PHA-based microporous articles and methods of forming same

Abstract

Provided are microporous and tough PHA-based articles having a knot and fibril structure, as well as processes for making these articles using a less than melt processing manner. In some embodiments, a method of forming a porous expanded PHA composite comprising a porous PHA material can include depositing a partially crystalline polyhydroxyalkanoate (PHA) polymer on a substrate at a deposition temperature below a melting temperature of the PHA polymer to form a PHA-substrate composite, and expanding the PHA-substrate composite at a temperature between the glass transition temperature of the PHA polymer and the melting temperature of the PHA polymer.

Description

Technical Field

[0001] The present disclosure generally relates to apparatuses, systems, and methods for forming polyhydroxyalkanoate (PHA)-based microporous articles. More specifically, the present disclosure relates to apparatuses, systems, and methods for forming PHA-based microporous articles having knots and fibrils using below-melting processing modes. Background Art

[0002] Polyhydroxybutyrate (PHB) is a sub-series of polyhydroxyalkanoates (PHA), which are biodegradable and biocompatible aliphatic polyesters. PHA is a thermoplastic polymer as a linear polyester, which can be produced naturally by various microorganisms or can be synthesized chemically. Due to its biodegradation path in the environment, PHA is considered a fully recyclable material.

[0003] PHB materials are subject to poor mechanical properties. Due to its high stereoregularity, crystallinity, and formation of large spherulites, PHB materials tend to be rigid and brittle. The thermal processing window of PHB materials is also narrow because its thermal decomposition temperature is close to its melting point. In addition, PHB materials have low melt strength, making their melt processing challenging.

[0004] Common ways to mitigate these challenges involve using low molecular weight PHA, blending with nucleating agents / other polymers, and using higher-cost PHA copolymers with limited thermal properties to improve processability and its final mechanical properties. However, these ways inherently limit the highest achievable mechanical properties, and any additional materials involved can have a significant impact on biodegradability, biocompatibility, cost, and potential processing paths; thus limiting its suitability in various high-demand applications.

[0005] PHA can also be synthesized chemically (Westlie et al. Synthetic biodegradable polyhydroxyalkanoates (PHAs): Recent advances and future challenges, Progress in Polymer Science 134 (2022) 101608). Chemical catalytic synthesis routes enable fine-tuning of the thermal and mechanical properties of polyesters by manipulating polymer stereomicrostructure, topology, and pendant group structure. The chemical catalytic route of PHA offers several advantages, such as: (i) synthesis precision (control of chain length (M n ) and , comonomer sequence, and architecture); (ii) tunable polymer stereomicrostructure (it, st, at, sb-tacticity, and R or S stereoconfiguration), molecular catalyst structure (symmetry and chirality; stereoselectivity), and copolymer structure; and (iii) scalability and speed of production (easy to process, fast reaction kinetics, which is usually associated with the catalytic ring-opening polymerization (ROP) process) (Westlie et al., supra). Monosubstituted or disubstituted alkyl or aryl groups on the PHA monomer increase the thermal stability of the resulting PHA polymer by suppressing cis-elimination (Zhou et al., Science 380, 64–69 (2023)). Examples of these substituted PHA polymers include, but are not limited to: poly(3-hydroxy-2,2-dimethylbutyrate) (P3H(Me)2B), poly(3-hydroxy-2,2-diethylbutyrate) (P3H(Et)2B). However, there is still a need for PHA-based articles that are microporous and have sufficient thermal and mechanical properties for a variety of applications. Summary of the Invention

[0006] According to one aspect (“Aspect 1”), the method includes: depositing a partially crystalline polyhydroxyalkanoate (PHA) polymer on a substrate at a deposition temperature below the melting temperature (T m ) of the PHA polymer to form a PHA-substrate composite, and swelling the PHA-substrate composite at a temperature between the glass transition temperature (T g ) and the melting temperature (T m ) of the PHA polymer to form a porous swollen PHA composite, the porous swollen PHA composite including a porous PHA material having a microstructure including a plurality of knots and a plurality of fibrils interconnected with the plurality of knots, wherein each fibril defines a fibril axis.

[0007] According to a further aspect for Aspect 1 (“Aspect 2”), wherein the fibril includes an extended chain crystal (ECC) of the PHA polymer oriented along the fibril axis, wherein the melting temperature of the extended chain crystal of the PHA polymer is higher than the T m of the PHA polymer before swelling.

[0008] According to a further aspect for Aspect 1 or Aspect 2 (“Aspect 3”), wherein depositing the partially crystalline PHA polymer includes dissolving the PHA polymer in a solvent to form a PHA solution, casting the PHA solution on the substrate, and at least partially crystallizing the PHA polymer by partially removing the solvent, adjusting the deposition temperature, or a combination thereof.

[0009] According to a further aspect with respect to aspects 1 to 3 (“aspect 4”), it further includes: separating the porous PHA material from the porous expanded PHA composite to form a self-supporting porous PHA material.

[0010] According to a further aspect with respect to any one of aspects 1 to 4 (“aspect 5”), wherein the porosity of the self-supporting porous PHA material is 25% to 99%.

[0011] According to a further aspect with respect to any one of aspects 1 to 5 (“aspect 6”), wherein the self-supporting porous PHA material is in the form of a film, tube, sheet, or three-dimensional shape.

[0012] According to a further aspect with respect to any one of aspects 1 to 6 (“aspect 7”), wherein the matrix tensile strength of the self-supporting porous PHA material in the machine direction (MD) and / or the transverse direction (TD) is at least 5 MPa.

[0013] According to a further aspect with respect to any one of aspects 1 to 7 (“aspect 8”), wherein the total surface area per unit mass of the self-supporting porous PHA material is 20 m 2 / g to 80 m 2 / g.

[0014] According to a further aspect with respect to any one of aspects 1 to 8 (“aspect 9”), wherein the PHA-substrate composite is expanded at a temperature 10 °C lower than the PHA polymer T m below.

[0015] According to a further aspect with respect to any one of aspects 1 to 9 (“aspect 10”), wherein the PHA-substrate composite is uniaxially expanded, biaxially expanded, or radially expanded.

[0016] According to a further aspect with respect to any one of aspects 1 to 10 (“aspect 11”), wherein the PHA-substrate composite is expanded at a rate of 1% / s to 1000% / s.

[0017] According to a further aspect with respect to any one of aspects 1 to 11 (“aspect 12”), wherein the expansion ratio of the PHA-substrate composite is 1:1.1 to 1:100.

[0018] According to a further aspect with respect to any one of aspects 1 to 12 (“aspect 13”), wherein the PHA polymer includes a monomer, homopolymer, or copolymer, and the monomer, homopolymer, or copolymer includes 3-hydroxybutyrate, 3-hydroxypentanoate, 4-hydroxybutyrate, 3-hydroxyhexanoate, or any combination thereof.

[0019] According to a further aspect (“Aspect 14”) of any one of Aspects 1 to 13, wherein the PHA polymer is: poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(4-hydroxybutyrate) (P4HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), or poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx).

[0020] According to a further aspect (“Aspect 15”) of any one of Aspects 1 to 14, it further includes: forming a modified PHA article by processing the porous expanded PHA composite or the self-supporting porous PHA material, wherein the processing includes: coating, imbibing, laminating, or any combination thereof, and wherein the modified PHA article is porous or non-porous.

[0021] According to a further aspect (“Aspect 16”) of any one of Aspects 1 to 15, it further includes: densifying the porous expanded PHA composite, the porous self-supporting porous PHA material, or the modified PHA article to form a densified PHA material.

[0022] According to a further aspect (“Aspect 17”) of Aspect 16, wherein the densified PHA material can detect an endotherm associated with the presence of extended-chain crystals of the PHA polymer.

[0023] According to a further aspect (“Aspect 18”) of Aspect 16 or Aspect 17, wherein the densifying includes applying heat, applying pressure, stretching, or any combination thereof.

[0024] According to a further aspect (“Aspect 19”) of any one of Aspects 1 to 16, wherein before deposition on a substrate, the PHA polymer further includes at least one pore-forming agent.

[0025] According to a further aspect (“Aspect 20”) of Aspect 19, it further includes removing the pore-forming agent before or after expanding the PHA-substrate composite.

[0026] According to a further aspect (“Aspect 21”) of any one of Aspects 1 to 16, wherein the substrate is a deformable substrate.

[0027] According to a further aspect (“Aspect 22”) of Aspect 21, wherein the deformable substrate is an expandable polymer.

[0028] According to a further aspect ("Aspect 23") of Aspect 21 or Aspect 22, wherein the deformable substrate comprises a material selected from the group consisting of: polytetrafluoroethylene (PTFE) tape, PTFE film, polyolefin tape, polyolefin film, expanded polyolefin film, ultra-high molecular weight polyethylene (UHMWPE) tape, UHMWPE film, and expanded UHMWPE film.

[0029] According to one aspect ("Aspect 24"), the porous polyhydroxyalkanoate (PHA) material is formed from a PHA polymer having a microstructure comprising a plurality of knots and a plurality of fibrils interconnected with the plurality of knots, the plurality of fibrils defining a fibril axis.

[0030] According to a further aspect ("Aspect 25") of Aspect 24, wherein the fibrils comprise a plurality of extended chain crystals of the PHA polymer oriented along the fibril axis, wherein the melting temperature of the extended chain crystals of the PHA polymer is higher than the T of the PHA polymer before expansion. m 。

[0031] According to a further aspect ("Aspect 26") of Aspect 24 or Aspect 25, wherein the molecular weight of the PHA polymer is from 30,000 g / mol to 10,000,000 g / mol.

[0032] According to a further aspect ("Aspect 27") of any one of Aspect 24 to Aspect 26, wherein the porosity of the porous PHA material is from 25% to 99%.

[0033] According to a further aspect ("Aspect 28") of any one of Aspect 24 to Aspect 27, wherein the porous PHA material is in the form of a film, a tube, a sheet, or a three-dimensional shape.

[0034] According to a further aspect ("Aspect 29") of any one of Aspect 24 to Aspect 28, wherein the matrix tensile strength of the porous PHA material in the machine direction (MD) and / or the transverse direction (TD) is at least 5 MPa.

[0035] According to a further aspect ("Aspect 30") of any one of Aspect 24 to Aspect 29, wherein the total surface area per unit mass of the porous PHA material is greater than 20 m 2 / g.

[0036] According to a further aspect ("Aspect 31") of any one of Aspect 24 to Aspect 30, wherein the PHA polymer comprises a monomer, a homopolymer, or a copolymer, the monomer, the homopolymer, or the copolymer comprising 3-hydroxybutyrate, 3-hydroxypentanoate, 4-hydroxybutyrate, 3-hydroxyhexanoate, or any combination thereof.

[0037] According to a further aspect (“Aspect 32”) of any one of Aspects 24 to 31, wherein the PHA polymer is: poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(4-hydroxybutyrate) (P4HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), or poly(3-hydroxybutyrate-co-hydroxyhexanoate) P(HB-co-HHx).

[0038] According to a further aspect (“Aspect 33”) of any one of Aspects 24 to 32, wherein the PHA polymer is blended with an additional polymer selected from: polylactic acid (PLA), poly(butylene adipate terephthalate) (PBAT), poly(butylene succinate) (PBS), cellulose, poly(glycolic acid) (PGA), polycaprolactone (PCL), poly(vinyl acetate) (PVAc), chitin, chitosan, starch, and any combination thereof.

[0039] According to one aspect (“Aspect 34”), the composite comprises a porous PHA material as described in any one of Aspects 24 - 33.

[0040] According to a further aspect (“Aspect 35”) of Aspect 34, wherein the PHA composite is microporous.

[0041] According to one aspect (“Aspect 36”), the article comprises a porous PHA material as described in any one of Aspects 24 - 33, or a composite as described in Aspects 34 and 35.

[0042] According to a further aspect (“Aspect 37”) of Aspect 36, wherein the article comprises a woven or non-woven support substrate.

[0043] According to one aspect (“Aspect 38”), the material comprises densified expanded polyhydroxyalkanoate, which exhibits an endotherm associated with the presence of straight-chain crystals of the remaining PHA polymer, wherein the porosity of the material is less than 10%.

[0044] According to one aspect (“Aspect 39”), the porous polyhydroxyalkanoate (PHA) material is formed from a PHA polymer of Formula I or Formula II:

[0045] or

[0046] Formula II:

[0047]

[0048] wherein R1 and R2 are independently H or C1-C6 alkyl or aryl; R3 is C1-C4 alkyl; X is 2-4; and n = 3000-100,000; and wherein the porous PHA material has a fibrillar microstructure comprising a plurality of interconnected nodes of fibrils or comprising only fibrils, and wherein the orientation of the fibrils defines a fibril axis.

[0049] According to a further aspect ( "Aspect 40") of Aspect 39, wherein the fibrils comprise a plurality of extended-chain crystals of the PHA polymer oriented along the fibril axis, wherein the melting temperature of the extended-chain crystals of the PHA polymer is higher than the T of the PHA polymer before expansion. m 。

[0050] According to a further aspect ( "Aspect 41") of Aspect 39 or Aspect 40, wherein the molecular weight of the PHA polymer is 30,000 g / mol to 10,000,000 g / mol.

[0051] According to a further aspect ( "Aspect 42") of any one of Aspects 39 to 41, wherein the porosity of the porous PHA material is 25% to 99%.

[0052] According to a further aspect ( "Aspect 43") of any one of Aspects 39 to 42, wherein the porous PHA material is in the form of a film, tube, sheet, monofilament, or three-dimensional shape.

[0053] According to a further aspect ( "Aspect 44") of any one of Aspects 39 to 43, wherein the matrix tensile strength of the porous PHA material in the machine direction (MD) and / or the transverse direction (TD) is at least 5 MPa.

[0054] According to a further aspect ( "Aspect 45") of any one of Aspects 39 to 44, wherein the total surface area per unit mass of the porous PHA material is greater than 20 m 2 / g.

[0055] According to a further aspect ( "Aspect 46") of any one of Aspects 39 to 45, wherein the PHA polymer comprises a monomer, homopolymer, or copolymer, the monomer, homopolymer, or copolymer comprising 3-hydroxybutyrate, 3-hydroxypentanoate, 4-hydroxybutyrate, 3-hydroxyhexanoate, 3-hydroxy-2,2-dimethylbutyrate, 3-hydroxy-2-methylbutyrate, 3-hydroxy-2-ethylbutyrate, 3-hydroxy-2-methyl-2-ethylbutyrate, 3-hydroxy-2,2-diethylbutyrate, or any combination thereof.

[0056] According to a further aspect (“Aspect 47”) of any one of Aspects 39 to 46, wherein the PHA polymer is: poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(4-hydroxybutyrate) (P4HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-hydroxyhexanoate) P(HB-co-HHx), poly(3-hydroxy-2,2-dimethylbutyrate), poly(3-hydroxy-2-methylbutyrate), poly(3-hydroxy-2-ethylbutyrate), poly(3-hydroxy-2,2-diethylbutyrate), or poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0057] According to a further aspect (“Aspect 48”) of any one of Aspects 39 to 47, wherein the PHA polymer is blended with an additional polymer selected from: polylactic acid (PLA), poly(butylene adipate terephthalate) (PBAT), poly(butylene succinate) (PBS), cellulose, polyglycolic acid (PGA), polycaprolactone (PCL), poly(vinyl acetate) (PVAc), chitin, chitosan, starch, and any combination thereof.

[0058] According to one aspect (“Aspect 49”), the composite comprises a porous PHA material as described in any one of Aspects 39 to 48.

[0059] According to a further aspect (“Aspect 50”) of Aspect 49, wherein the PHA composite is microporous.

[0060] According to one aspect (“Aspect 51”), the article comprises a porous PHA material as described in any one of Aspects 39 to 48, or a composite as described in Aspect 49 or Aspect 50.

[0061] According to a further aspect (“Aspect 52”) of Aspect 51, in the form of a film, tube, sheet, monofilament article, or three-dimensional shape.

[0062] According to a further aspect (“Aspect 53”) of Aspect 52, wherein the monofilament article is dental floss, a medical suture, or fishing line.

[0063] According to a further aspect (“Aspect 54”) of Aspect 51, wherein the article comprises a woven or non-woven support substrate.

[0064] According to one aspect (“Aspect 55”), a woven or knitted fabric comprises a porous PHA as described in any one of Aspects 39 to 48.

[0065] According to one aspect (“Aspect 56”), the wearable garment includes a woven or knitted fabric as described in Aspect 55. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to further understand the present disclosure. The drawings illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The drawings are not necessarily to scale and may be enlarged to illustrate various aspects of the present disclosure. In this regard, the drawings should not be considered limiting.

[0067] Figure 1A and 1B are scanning electron microscope (SEM) micrographs of the porous poly(3-hydroxybutyrate) film prepared in Example 11 at two different magnifications according to the embodiments disclosed herein;

[0068] Figure 2A and 2B are scanning electron microscope (SEM) micrographs of the porous poly(3-hydroxybutyrate) film prepared in Example 12 at two different magnifications according to the embodiments disclosed herein;

[0069] Figure 3A and 3B are scanning electron microscope (SEM) micrographs of the porous poly(3-hydroxybutyrate) film prepared in Example 14 at two different magnifications according to the embodiments disclosed herein;

[0070] Figure 4 is a differential scanning calorimetry (DSC) graph of the cast P3HB film and the resulting biaxially expanded P3HB film described in Example 14 according to the embodiments disclosed herein;

[0071] Figure 5A and 5B are scanning electron microscope (SEM) micrographs of the porous poly(3-hydroxybutyrate) film prepared in Example 15 at two different magnifications according to the embodiments disclosed herein;

[0072] Figure 6A and 6B are scanning electron microscope (SEM) micrographs of the porous poly(3-hydroxybutyrate) film prepared in Example 16 at two different magnifications according to the embodiments disclosed herein;

[0073] Figure 7A and 7Bare scanning electron microscope (SEM) micrographs of the porous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) film described in Example 17 at two different magnifications, according to embodiments disclosed herein;

[0074] Figure 8 is a differential scanning calorimetry (DSC) plot of the cast PHBV film and the resulting biaxially expanded PHBV film described in Example 17, according to embodiments disclosed herein;

[0075] Figure 9 are scanning electron microscope (SEM) micrographs of the porous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) film described in Example 19, according to embodiments disclosed herein;

[0076] Figure 10 are scanning electron microscope (SEM) micrographs of the porous poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) film described in Example 20, according to embodiments disclosed herein; and

[0077] Figure 11A and 11B are scanning electron microscope (SEM) micrographs of the porous poly(3-hydroxybutyrate) / polyethylene composite film described in Example 22, according to embodiments disclosed herein. Figure 11A is a top view of the composite, showing that the porous P3HB layer has a microstructure of knots and fibrils. Figure 11B is a cross-sectional view of the porous P3HB / PE composite, showing the porous P3HB layer and the porous polyethylene layer. DETAILED DESCRIPTION

[0078] Definitions and Terms

[0079] The present disclosure is not intended to be construed in a limiting manner. For example, the terms used in this application should be construed broadly in the context of the meanings given to such terms in the art. It will be understood that the terms "melt temperature", "melting temperature", and "melt point" may be used interchangeably herein.

[0080] For imprecise terms, the terms "about" and "approximately" are used interchangeably and are intended to mean that a measured value includes the recited value and also includes any measured value that is reasonably close to the recited value. As would be understood and readily ascertainable by one of ordinary skill in the relevant art, a measured value that is reasonably close to the recited value deviates from the recited value by a relatively small amount. Such deviation may be attributable to measurement error, differences in measurement and / or manufacturing equipment calibration, human error in reading and / or setting measurements, fine-tuning for measurement differences associated with other components to optimize performance and / or structural parameters, particular implementation scenarios, imprecise adjustment and / or operation of objects by persons or machines, etc. If it is determined that a person of ordinary skill in the relevant art cannot readily ascertain the value of such reasonably small differences, the terms "about" and "approximately" can be understood to mean plus or minus 10% of the recited value.

[0081] As used herein, "polyhydroxyalkanoate (PHA)" is a linear biodegradable polyester that can be produced by various microorganisms or can be synthesized chemocatalytically (Westlie et al., supra).

[0082] In some embodiments, PHA polymers suitable for preparing the porous articles of the present invention include those shown in Formula I and Formula II:

[0083] Formula I

[0084]

[0085] Or

[0086] Formula II

[0087]

[0088] wherein R1 and R2 are independently H, or a C1 to C6 alkyl or aryl group;

[0089] R3 is a C1 to C7 alkyl or aryl group;

[0090] X is from 2 to 4; and

[0091] n = 3000 to 100,000.

[0092] In some embodiments, both R1 and R2 are hydrogen. In some embodiments, at least one of R1 and R2 is a C1 to C6 alkyl or aryl group. In some embodiments, both R1 and R2 are C1 to C6 alkyl or aryl groups. In some embodiments, both R1 and R2 are C1 to C6 alkyl groups.

[0093] The PHA polymers used to prepare the microporous PHA articles of the present invention having a fibrillated microstructure (i.e., interconnected fibrils or substantially only fibrils) can be PHA homopolymers, PHA copolymers, or PHA terpolymers.

[0094] PHA is classified based on the carbon number of its monomer units. Some short-chain-length PHAs composed of 3-5 carbon monomers include: poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(4-hydroxybutyrate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate). Medium-chain-length PHAs having 6-14 carbon monomers include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate), while long-chain-length PHAs contain at least 15 carbon monomers (Tan et al., Polymers 2014, 6:706-754).

[0095] PHA can include those in which the α-hydrogen on the PHA monomer is mono- or di-substituted with an alkyl or aryl group, thereby increasing the thermal stability of the resulting PHA polymer by inhibiting cis-elimination (Zhou et al., Science 380, 64–69 (2023)). Examples of these substituted PHA polymers include, but are not limited to: poly(3-hydroxy-2,2-dimethylbutyrate) (P3H(Me)2B), poly(3-hydroxy-2,2-diethylbutyrate) (P3H(Et)2B).

[0096] A variety of linear PHA homopolymers and copolymers are semi-crystalline. The relative crystallinity can be determined by various well-known techniques, including but not limited to: density measurement, differential scanning calorimetry, X-ray diffraction, infrared spectroscopy, and nuclear magnetic resonance (NMR).

[0097] This method produces a knotted and fibrillar microstructure, where the fibrils contain straight molecular chains with the PHA polymer oriented along the longitudinal axis of the fibrils. The oriented chains can be in the form of extended-chain crystals (ECC). As used herein, "extended-chain crystal" refers to a crystalline form in which the linear PHA polymer chains are oriented in a highly extended conformation. Extended-chain crystals are the thermodynamically most stable form of the polymer material. Thus, the melting temperature of the extended-chain crystals of the PHA polymer will be higher than the melting temperature of the PHA polymer before swelling. Differential scanning calorimetry (DSC) can be used to determine the presence of extended-chain crystals.

[0098] As used herein, "partially crystalline" describes a semi-crystalline polymer with a crystallinity range of about 5% to less than 90%.

[0099] Examples of various PHAs and their related melting temperatures and glass transition temperatures are provided in Table 1 below.

[0100] Table 1

[0101] Melting temperature (T m ) and glass transition temperature (T g )

[0102]

[0103]

[0104] [1] Sudesh, K., Abe, H., Doi, Y., (2000), Progress in Polymer Science, 25(10): 1503 - 1555.

[0105] [2] Martinez, J.I., Verdu, I., Fenollar, O., Sanchez - Nacher, L., Balart, R. and Quiles - Carrillo, (2020), Polymers, 12, 1118.

[0106] [3] Luo, L., Wei, X. and Chen, GQ., (2009), Journal of Biomaterials Science, 20, 1537 - 1553.

[0107] [4] Hori, Y., Yamaguchi, A. and Hagiwara, T., (1995), Polymer, 36, 24, 4703 - 4705.

[0108] [5] Zhou, L., Zhang, Z., Shi, C., Scoti, M., Barange, DK., Gowda, RR. And Chen, EYX., (2023), Science, 380, 64 - 69.

[0109] Description of Embodiments

[0110] The present disclosure relates to PHA - based microporous and tough articles having a node and fibril structure, and to processes for manufacturing these articles using below - the - melt processing methods. PHA - based microporous articles processed by below - the - melt methods have improved processibility and mechanical properties and help keep PHA polymers as a bio - derived sustainable material option.

[0111] In some embodiments, PHA-based microporous intermediates can be produced by solvent-induced phase inversion and thermal-induced phase inversion, where all processes are carried out below the melting temperature of the selected PHA. The intermediate can be produced by blending a starting PHA homopolymer and / or copolymer with a solvent and / or plasticizer, or by dissolving the starting PHA homopolymer and / or copolymer using a solvent and / or plasticizer.

[0112] In some embodiments, subsequently, the intermediate can be stretched or expanded at a temperature above the glass transition temperature of the selected PHA and below the melting temperature of the selected PHA. The stretching can be carried out in a uniaxial manner, a biaxial manner, and / or an ordered manner. The final stretched article has a nodule and fibril microstructure, where the fibrils contain oriented molecular chains along the longitudinal axis of the fibrils, resulting in improved mechanical properties. PHA is a surface degradation material. The degradation rate of the final article can also be controlled by its properties, by changing the processing parameters of stretching and / or the initial properties of the PHA. For example, the degradation rate can be controlled by the surface area, molecular weight, crystallinity, etc. of the PHA.

[0113] In some embodiments, a method for forming a porous expanded PHA composite includes: depositing a partially crystalline PHA polymer on a substrate at a deposition temperature below the melting temperature of the PHA polymer to form a PHA-substrate composite. Depositing the PHA polymer can include: dissolving the PHA polymer in a solvent to form a PHA solution, casting the PHA solution on the substrate, and at least partially crystallizing the PHA polymer by partially removing the solvent, adjusting the deposition temperature, or a combination thereof.

[0114] In some embodiments, the method can further include: expanding the PHA-substrate composite at a temperature between the glass transition temperature of the PHA polymer and the melting temperature of the PHA polymer. The formed PHA composite can include a porous PHA material having a microstructure with a plurality of nodules and a plurality of fibrils interconnected with the plurality of nodules, and the fibrils define a fibril axis. The fibrils of the porous expanded PHA composite can include extended chain crystals (ECC) of the PHA polymer oriented along the fibril axis. The melting temperature of the extended chain crystals of the PHA polymer can be higher than the melting temperature of the PHA polymer before expansion. The PHA composite can be expanded uniaxially, biaxially, or radially.

[0115] The semi-crystalline PHA polymer may include short-chain, medium-chain, and long-chain PHA monomers, homopolymers, or copolymers. In some embodiments, the PHA polymer may include monomers, homopolymers, or copolymers that include 3-hydroxybutyrate, 3-hydroxyvalerate, 4-hydroxybutyrate, 3-hydroxyhexanoate, or any combination thereof. In some embodiments, the PHA copolymer may include monomers such as 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate, and combinations thereof. In some embodiments, the PHA polymer may be: poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(4-hydroxybutyrate) (P4HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), or poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx). In some embodiments, the PHA polymer may be: poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), or poly(3-hydroxybutyrate-co-3-hydroxydecanoate).

[0116] In some embodiments, prior to deposition on the substrate, the PHA polymer may include at least one pore former. In some cases, the pore former may be removed before swelling the PHA-substrate composite. In some cases, the pore former may be removed after swelling the PHA-substrate composite.

[0117] The substrate may be deformable. In some embodiments, the substrate may be an expandable polymer different from the PHA polymer. In some embodiments, the substrate may include a material selected from the group consisting of: polytetrafluoroethylene (PTFE) tape, PTFE film, polyolefin tape, polyolefin film, expanded polyolefin film, ultra-high molecular weight polyethylene (UHMWPE) tape, UHMWPE film, and expanded UHMWPE film.

[0118] Swelling of the PHA-substrate composite may be carried out at a temperature that is about 5°C to 15°C below the melting temperature of the PHA polymer, or about 6°C to 14°C below the melting temperature of the PHA polymer, or about 7°C to 13°C below the melting temperature of the PHA polymer, or about 8°C to 12°C below the melting temperature of the PHA polymer, or about 9°C to 11°C below the melting temperature of the PHA polymer, or any temperature covered by the foregoing ranges. In some embodiments, the PHA-substrate composite may be swollen at a temperature about 10°C below the melting temperature of the PHA polymer.

[0119] The PHA-substrate can be expanded at a rate of: about 1% / s to about 1000% / s, or about 2% / s to about 950% / s, or about 3% / s to about 900% / s, or about 4% / s to about 850% / s, or about 5% / s to about 800% / s, or about 6% / s to about 750% / s, or about 7% / s to about 700% / s, or about 8% / s to about 650% / s, or about 9% / s to about 600% / s, or about 10% / s to about 550% / s, or about 15% / s to about 500% / s, or about 20% / s to about 450% / s, or about 25% / s to about 400% / s, or about 30% / s to about 350% / s, or about 35% / s to about 300% / s, or about 40% / s to about 250% / s, or about 45% / s to about 200% / s, or about 50% / s to about 150%, or any rate covered by the foregoing ranges.

[0120] The expansion ratio of the PHA-substrate composite can be: about 1:1.1 to about 1:100, or about 1:1.2 to about 1:95, or about 1:1.3 to about 1:90, or about 1:1.4 to about 1:85, or about 1:1.5 to about 1:80, or about 1:1.6 to about 1:75, or about 1:1.7 to about 1:70, or about 1:1.8 to about 1:65, or about 1:1.9 to about 1:60, or about 1:2 to about 1:55, or about 1:3 to about 1:50, or about 1:4 to about 1:45, or about 1:5 to about 1:40, or about 1:6 to about 1:35, or about 1:7 to about 1:30, or about 1:8 to about 1:25, or about 1:9 to about 1:20, or about 1:10 to about 1:15, or any expansion ratio covered by the foregoing ranges.

[0121] In some embodiments, the method of forming a porous expanded PHA composite may further include: separating the porous PHA material from the porous expanded PHA composite to form a self-supporting porous PHA material. The self-supporting porous PHA material can be in the form of a film, tube, sheet, or three-dimensional shape.

[0122] The porosity of the self-supporting porous PHA material can be: about 25% to about 99%, or about 30% to about 98.5%, or about 35% to about 98%, or about 40% to about 97.5%, or about 45% to about 97%, or about 50% to about 96.5%, or about 55% to about 96%, or about 60% to about 95.5%, or about 65% to about 95%, or about 66% to about 94.5%, or about 67% to about 94%, or any porosity covered by the foregoing ranges.

[0123] The matrix tensile strength of the self-supporting porous PHA material in the machine direction (MD) and / or the transverse direction (TD) can be at least 5 MPa. In some embodiments, the matrix tensile strength of the self-supporting porous PHA material in the MD or TD can be at least 10 MPa, or at least 15 MPa, or at least 20 MPa, or at least 25 MPa.

[0124] In some embodiments, the total surface area (specific surface area) per unit mass of the self-supporting porous PHA material can be: about 1 m 2 / g to about 150 m 2 / g, or about 1 m 2 / g to about 100 m 2 / g, or about 5 m 2 / g to about 95 m 2 / g, or about 10 m 2 / g to about 90 m 2 / g, or about 15 m 2 / g to about 85 m 2 / g, or about 20 m 2 / g to about 80 m 2 / g, or about 25 m 2 / g to about 75 m 2 / g, or about 26 m 2 / g to about 74 m 2 / g, or about 27 m 2 / g to about 73 m 2 / g, or any specific surface area covered by the foregoing ranges.

[0125] In some embodiments, the method of forming the porous expanded PHA composite can further include: forming a modified PHA article by processing the porous expanded PHA composite or the self-supporting porous PHA material. The processing can include: coating, liquid absorption, lamination, or any combination thereof. In some cases, the modified PHA article can be porous. In some cases, the modified PHA article can be non-porous.

[0126] In some embodiments, the porous expanded PHA composite, the porous self-supporting porous PHA material, or the modified PHA article can be densified to form a densified PHA material. The densification can include applying heat, applying pressure, stretching, or any combination thereof. The densified PHA material can detect an endotherm associated with the presence of the straight-chain crystals of the PHA polymer.

[0127] In some embodiments, a porous polyhydroxyalkanoate (PHA) material having a plurality of knots and a plurality of fibrils interconnected with the plurality of knots may be formed from a PHA polymer. The plurality of fibrils may define a fibril axis and may include a plurality of extended-chain crystals of the PHA polymer oriented along the fibril axis. Prior to swelling the PHA polymer, the melting temperature of the extended-chain crystals of the PHA polymer may be higher than the melting temperature of the PHA polymer. The porous PHA material may be in the form of a film, a tube, a sheet, a monofilament, or a three-dimensional shape.

[0128] The PHA polymer may include a monomer, a homopolymer, or a copolymer, the monomer, homopolymer, or copolymer including 3-hydroxybutyrate, 3-hydroxypentanoate, 4-hydroxybutyrate, 3-hydroxyhexanoate, or any combination thereof. In some embodiments, the PHA polymer may be: poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxypentanoate) (PHBV), poly(4-hydroxybutyrate) (P4HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), or poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx).

[0129] The molecular weight of the PHA polymer may be: from about 30,000 g / mol to about 10,000,000 g / mol, or from about 30,000 g / mol to about 10,000,000 g / mol, or from about 40,000 g / mol to about 9,000,000 g / mol, or from about 50,000 g / mol to about 8,000,000 g / mol, or from about 60,000 g / mol to about 7,000,000 g / mol, or from about 70,000 g / mol to about 6,000,000 g / mol, or from about 80,000 g / mol to about 5,000,000 g / mol, or from about 90,000 g / mol to about 4,000,000 g / mol, or from about 100,000 g / mol to about 3,000,000 g / mol, or from about 110,000 g / mol to about 2,000,000 g / mol, or from about 120,000 g / mol to about 1,000,000 g / mol, or from about 130,000 g / mol to about 900,000 g / mol, or any molecular weight covered by the foregoing ranges.

[0130] In some embodiments, the PHA polymer may be blended with additional polymers selected from: polylactic acid (PLA), poly(butylene adipate terephthalate) (PBAT), poly(butylene succinate) (PBS), cellulose, polyglycolic acid (PGA), polycaprolactone (PCL), poly(vinyl acetate) (PVAc), chitin, chitosan, starch, and any combination thereof.

[0131] In some embodiments, the porosity of the porous PHA material may be: about 25% to 99%, or about 30% to about 98.5%, or about 35% to about 98%, or about 40% to about 97.5%, or about 45% to about 97%, or about 50% to about 96.5%, or about 55% to about 96%, or about 60% to about 95.5%, or about 65% to about 95%, or about 66% to about 94.5%, or about 67% to about 94%, or any porosity covered by the foregoing ranges.

[0132] In some embodiments, the matrix tensile strength of the porous PHA material in the machine direction (MD) and / or the transverse direction (TD) may be at least 5 MPa. In some embodiments, the matrix tensile strength of the self-supporting porous PHA material in the MD or TD may be at least 10 MPa, or at least 15 MPa, or at least 20 MPa, or at least 25 MPa.

[0133] In some embodiments, the total surface area (specific surface area) per unit mass of the porous PHA material is about 1 m 2 / g to about 150 m 2 / g, or about 1 m 2 / g to about 100 m 2 / g, or about 5 m 2 / g to about 95 m 2 / g, or about 10 m 2 / g to about 90 m 2 / g, or about 15 m 2 / g to about 85 m 2 / g, or about 20 m 2 / g to about 80 m 2 / g, or about 25 m 2 / g to about 75 m 2 / g, or about 26 m 2 / g to about 74 m 2 / g, or about 27 m 2 / g to about 73 m 2 / g. In an exemplary embodiment, the total surface area (specific surface area) per unit mass of the porous PHA material is greater than about 20 m 2 / g, or any specific surface area covered by the foregoing ranges.

[0134] In some embodiments, the mass / area of the porous PHA material can be from about 0.1 g / m 2 to about 100 g / m 2 or from about 0.1 g / m 2 to about 50 g / m 2 or from about 0.5 g / m 2 to about 50 g / m 2 or from about 0.5 g / m 2 to about 10 g / m 2 or from about 0.7 g / m 2 to about 9 g / m 2 from about 0.9 g / m 2 to about 8 g / m 2 from about 1 g / m 2 to about 7 g / m 2 from about 1.1 g / m 2 to about 6 g / m 2 from about 1.2 g / m 2 to about 5 g / m 2 from about 1.5 g / m 2 to about 4.5 g / m 2 or any mass / area covered by the foregoing ranges.

[0135] In some embodiments, the porous PHA material can be in the form of a film with a thickness of from about 5 μm to about 500 μm, or a thickness of from about 5 μm to about 100 μm, or from about 6 μm to about 90 μm, from about 7 μm to about 80 μm, from about 8 μm to about 70 μm, from about 9 μm to about 65 μm, from about 10 μm to about 60 μm, from about 11 μm to about 55 μm, or any thickness covered by the foregoing ranges.

[0136] In some embodiments, the ATEQ air flow rate of the porous PHA material can be from about 0.1 L / hr to about 1000 L / hr, or from about 0.1 L / hr to about 400 L / hr, or from about 0.5 L / hr to about 390 L / hr, or from about 1 L / hr to about 380 L / hr, or from about 1.5 L / hr to about 370 L / hr, or from about 2 L / hr to about 360 L / hr, or from about 2.5 L / hr to about 350 L / hr, or from about 2.9 L / hr to about 340 L / hr, or from about 3 L / hr to about 330 L / hr, or any ATEQ air flow rate covered by the foregoing ranges.

[0137] In some embodiments, the water entry pressure (WEP) of the porous PHA material is about 7 kPa.

[0138] In some embodiments, the composite may comprise a porous PHA material as described herein. The composite may be microporous. In some embodiments, the article may comprise the porous PHA material, or a composite comprising the porous PHA material. The article may comprise a woven or non-woven support substrate.

[0139] In some embodiments, a material comprising a densified expanded polyhydroxyalkanoate may exhibit an endotherm associated with the presence of extended-chain crystals of the residual PHA polymer, and the porosity may be less than 10%.

[0140] In some embodiments, a PHA-based microporous article having a fibrillar microstructure is in the form of a microporous monofilament. The monofilament can be used to make woven and knitted articles, fabrics, medical sutures, fishing lines, dental floss / tape, and the like. The PHA monofilament may include various further modifications to introduce additional texture or coarseness (such further modifications include, for example, twisting, folding, knotting, embossing, forming a ribbed structure, incorporating abrasive fillers, and combinations thereof), especially for applications such as medical sutures, dental floss / tape, and the like. In one embodiment, the PHA monofilament can be formed by using the general method described in International Patent Application Publication No. WO2022 / 103783 to Minor, R. (describing the preparation of porous ultra-high molecular weight polyethylene (UHMWPE) dental floss), slitting a PHA membrane into strips of appropriate size for the desired application. In various embodiments, the PHA strips can be stacked and subjected to further machining modifications such as twisting, folding, knotting, embossing, calendering, additional stretching or expansion, and various combinations thereof to obtain the desired properties for the target application. In some embodiments, these further machining modification steps can be carried out above or below the melting of the PHA polymer. In a further embodiment, these further machining modifications are carried out below the melting of the PHA polymer.

[0141] In some embodiments, the porous PHA monofilament further comprises a functionalizing additive such as particulate fillers, flavorants, caries-preventive agents, colorants, coatings (waxes, silicones, etc.), radiopaque materials, and the like. The general methods for preparing dental floss / tape based on non-PHA polymers may be followed (see, for example, U.S. Patent Publication No. 2011 / 0214683A1 to Hardesty, and U.S. Patent No. 8,522,796B2 to Ochs; U.S. Patent No. 7,854,235B2 to Blanchard et al., U.S. Patent No. 8,048,111B2 to Lutz et al., U.S. Patent No. 7,174,903B2 to Longoni, E., U.S. Patent No. 7,060,354B2 to Baillie et al., and U.S. Patent No. 6,289,904B1 to Suhonen et al.) to introduce structural features and functionalizing additives / coatings for dental floss / tape into the PHA monofilaments of the present invention having a fibrillated microstructure.

[0142] In a further embodiment, the porous PHA monofilament is used to manufacture a fabric. The fabric may comprise one or more porous PHA monofilament yarns, porous PHA multifilament yarns, or combinations thereof. Such yarns may be formed from the above-described microporous PHA monofilaments and other materials such as: wool, cotton, silk, linen, hemp, hair from various animals, angora, sisal, ramie, acrylics, polyesters, polyamides, polyaramids, polyurethanes, acetate, rayon, polybenzimidazole, polybenzoxazole, lyocell, modified acrylics, polyvinylidene chloride, carbon, glass, cellulose, cellulose acetate, cellulose esters, elastomers, or any combination thereof.

[0143] Test Methods

[0144] Average Thickness Measurement

[0145] The thickness is measured by placing the sample between two Mitutoyo contact thickness gauges (Mitutoyo America Corporation, Aurora, Illinois). The average of three measurements is reported and used in the % porosity calculation below.

[0146] % Porosity Calculation

[0147] By using 1.2 g / cm 3Calculate the % porosity of the film as the bulk density of the sample. Die cut samples using a 25 mm circular die. Weigh each sample using an electronic balance (Mettler Toledo, Columbus, OH). The density of the sample can be calculated using the following equation:

[0148]

[0149] where ρ = density (g / cm 3 ), m = mass (g), A = area of the circular die (cm 2 ), and t = thickness (cm).

[0150] Report the average of three measurements.

[0151] Differential Scanning Calorimetry (DSC):

[0152] Collect DSC data using a TA Instruments Discovery DSC (TA Instruments–Waters LLC, Newcastle, Delaware) between -50 °C and 200 °C at a heating rate of 10 °C / min. The film sample was prepared by punching a 4 mm disc and placing it in a pan with the lid tightened so that the film was sandwiched between the pan and the lid.

[0153] Scanning Electron Micrograph (SEM)

[0154] Image the SEM samples using a Hitachi FlexSEM 1000II (Hitachi High-Tech America, Inc., Schaumburg, Illinois) at 1.0 to 10 kV.

[0155] Tensile Testing

[0156] Measure the matrix tensile strength (MTS) by measuring the response of stress to a constant uniaxial displacement rate on a dynamic mechanical analyzer (DMA) using an axial test (model: RSA-G2, manufactured by TA Instruments–Waters LLC, Newcastle, Delaware, USA). Die cut rectangular specimens of the sample with a width of 4.7 mm. The DMA is equipped with a film / fiber tensile fixture. Control the gauge length under the same test conditions at room temperature (about 22 °C). Place the prepared sample on the DMA fixture with a gauge length of 10 mm. The axial test consists of applying a constant displacement rate of 0.1 mm / s while measuring the instantaneous axial force.

[0157] The matrix tensile strength is calculated using the following equation: MTS = (maximum stress / cross-sectional area) * (true density of the sample / bulk density of the sample)

[0158] Airflow Measurement

[0159] Airflow is a test method for measuring the volumetric flow rate of air passing through a sample. Each sample is clamped between two plates, each with a #210 or equivalent O-ring, and there is an opening between the O-rings, creating a sealed area of 2.99 cm 2 in the flow path. The holes in the downstream-side flow path have a grid support structure across them. Using [ATEQ Corp., Livonia, Michigan] a Premier D Compact Flow Tester or equivalent equipment, the airflow rate (L / hour) through each sample is measured by applying an air pressure difference of 1.2 kPa (12 mbar) across the sample. The reported results are the average of three measurements.

[0160] Specific Surface Area Measurement

[0161] Brunauer-Emmett-Teller (BET) surface area analysis using a Quantachrome NOVAtouch LX4 (Anton Paar GmbH, Germany) is used to measure the specific surface area of the sample.

[0162] Water Entry Pressure (WEP) Measurement

[0163] Water penetration pressure provides a test method for water intrusion through a membrane. The test sample is clamped between a pair of test plates. The lower plate can apply pressure to a portion of the sample using water. A pH test strip is placed on top of the sample on the non-pressurized side between the disks as an indicator of water intrusion. Subsequently, the sample is pressurized in small increments and waited for 10 seconds after each pressure change until a color change in the pH test strip indicates the first sign of water entry. The water pressure at penetration or intrusion is recorded as the water penetration pressure. The test results are taken from the center of the test sample to avoid false results that may occur due to edge damage.

[0164] Weight-Average Molecular Weight by Size Exclusion Chromatography (SEC)

[0165] The weight-average molecular weight was determined as follows: Using a Malvern OMNISEC Reveal multi-detector SEC (Malvern PANalytical, Westborough, Massachusetts) with Shodex (Showa Denko America, Inc., New York, New York) columns KF-806L, KF807L, and KF-803, with a chloroform (Sigma-Aldrich, St. Louis, Missouri; GPC grade) solvent flow rate of 0.8 mL / min, an injection volume of 100 μL, a concentration of 2 - 3 mg / mL, at 30 °C.

[0166] Example

[0167] Example 1: Preparation of Poly(3-hydroxybutyrate) (P3HB) Solution

[0168] At room temperature (about 22 °C) and under vacuum, 10 grams of P3HB polymer (Biomer, Bavaria, Germany) was dried for 24 hours. The average molecular weight of the polymer was determined to be 1400 kDa. Subsequently, in a jacketed glass reactor with a PTFE stirrer paddle, at 75 °C under reflux conditions, the P3HB polymer was dissolved in 100 mL of chloroform (Sigma Aldrich, St. Louis, Missouri) for 1 hour. The resulting solution was aged at room temperature (about 22 °C) for 24 hours.

[0169] Example 2: Preparation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Solution

[0170] At room temperature (about 22 °C) and under vacuum, 10 grams of PHBV polymer (Tianan Biomaterials Co., Ltd., Zhejiang, China) with 3 mol% modification (i.e., 3 mol% of 3-hydroxyvalerate) was dried for 24 hours. According to the supplier, the average molecular weight of the polymer was 400 kDa. Subsequently, the PHBV polymer was mixed with 100 mL of chloroform (Sigma Aldrich) and dissolved in a jacketed glass reactor with a PTFE stirrer paddle at 65 °C under reflux conditions for 1 hour. The resulting solution was aged at room temperature (about 22 °C) for 24 hours.

[0171] Example 3: Preparation of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB / PHBH) Solution

[0172] At 75 °C, under reflux conditions, in a jacketed glass reactor with a PTFE stirrer paddle, 1 g of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) polymer (Sigma Aldrich) with 15.2 mol% modification (15.2 mol% 3-hydroxyhexanoate) and an average molecular weight of 580 kDa according to the manufacturer and 9 g of poly(3-hydroxybutyrate) (Biomer, Bayern, Germany) were dissolved together in 100 mL of chloroform for 1 hour. The resulting solution was aged at room temperature (about 22 °C) for 24 hours.

[0173] Example 4: Preparation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) / Polyethylene Glycol (PEG) Solution

[0174] To the 10% w / v PHBV solution prepared in Example 2, 2.4 g of a polyethylene glycol polymer (Sigma Aldrich) with an average molecular weight of 8 kDa according to the supplier was added and dissolved at room temperature (about 22 °C) for 24 hours with magnetic stirring. In the final solution, the ratio of the weight of PHBV to the weight of PEG was 5:1.

[0175] Example 5: Preparation of Poly(3-hydroxybutyrate) Cast Film on a Polytetrafluoroethylene (PTFE) Substrate, Using Methanol to Perform Non-Solvent Induced Phase Separation (NIPS)

[0176] A porous PTFE tape (thickness 258 μm, porosity 28%) was prepared according to the method of U.S. Patent No. 3,953,566 assigned to Gore. The porous PTFE tape was attached to a glass plate and then spin-coated with the P3HB solution (15 mL) prepared in Example 1 using a 254 μm drawdown bar. Subsequently, the P3HB-coated PTFE tape was immediately transferred to a bath filled with methanol (VWR International, LLC, Radnor, Pennsylvania) at room temperature (about 22 °C) for poor solvent-induced phase separation. The P3HB-coated PTFE tape was kept in the methanol bath for at least 5 minutes until the solvent exchange was complete. The solvent-exchanged P3HB / PTFE tape was removed from the bath and air-dried at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0177] Example 6: Preparation of Poly(3-hydroxybutyrate) Cast Film on a Polyethylene (PE) Substrate, Using Methanol to Perform Non- Solvent Induced Phase Separation

[0178] On a porous ultra-high molecular weight polyethylene (PE) tape with a thickness of 185 μm and a porosity of 25% (prepared according to U.S. Patent No. 10,577,468 attributed to Sbriglia), the P3HB solution (10 mL) prepared in Example 1 was coated using a 254-μm drawdown bar. The P3HB-coated PE tape was immediately immersed in a bath filled with methanol (VWR International, LLC) at room temperature (about 22 °C) to perform poor-solvent-induced phase separation. The P3HB-coated PE tape was kept in this methanol bath for 5 minutes until the solvent exchange was completed. The solvent-exchanged P3HB / PE tape was removed from the bath and air-dried at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0179] Example 7: Preparation of Poly(3-hydroxybutyrate) Cast Film on a Polyethylene (PE) Substrate, Using Methanol to Perform Non- Solvent Induced Phase Separation

[0180] Using a 254-μm drawdown bar, the P3HB solution prepared in Example 1 was coated on a porous ultra-high molecular weight polyethylene (UHMWPE) tape with a thickness of 360 μm and a porosity of 26% (prepared according to U.S. Patent No. 10,577,468 attributed to Sbriglia). The P3HB-coated PE tape was immediately immersed in a bath filled with methanol (VWR International, LLC) at room temperature (about 22 °C) to perform poor-solvent-induced phase separation. The P3HB-coated PE tape was kept in this methanol bath for 5 minutes until the solvent exchange was completed. The solvent-exchanged P3HB / PE tape was removed from the bath and air-dried at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0181] Example 8: Preparation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Cast Film on a Polyethylene (PE) Substrate, Using Isopropanol to Perform Non-Solvent Induced Phase Separation

[0182] Using a 254-μm thick drawdown bar, the PHBV solution (15 mL) prepared in Example 2 was coated onto a porous ultra-high molecular weight polyethylene (UHMWPE) tape with a thickness of 185 μm and a porosity of 25% (prepared according to U.S. Patent No. 10,577,468 attributed to Sbriglia). At room temperature (about 22 °C), the PHBV-coated PE tape was immediately immersed in a bath filled with isopropanol (VWR International, LLC). The solvent-exchanged PHBV / PE tape was kept in the isopropanol bath for 5 minutes to ensure solvent exchange. The solvent-exchanged PHBV / PE tape was removed from the bath and air-dried at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0183] Example 9: Preparation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) / Polyethylene Glycol (PEG) Cast Film on a Polyethylene Substrate

[0184] Using a 254 μm draw bar, coat the PHBV / PEG solution prepared in Example 4 onto a porous ultra-high molecular weight polyethylene (UHMWPE) tape with a thickness of 185 μm and a porosity of 25% (prepared according to U.S. Patent No. 10,577,468 attributed to Sbriglia). Air dry the PHBV / PEG-coated PE tape at room temperature (about 22 °C) for 24 hours to remove the chloroform solvent. Immerse the dried PHBV / PEG-coated PE tape in a reverse osmosis water bath at room temperature (about 22 °C) for 24 hours to remove the PEG. Subsequently, dry the PHBV-coated PE tape under vacuum at room temperature (about 22 °C) for 24 hours.

[0185] Example 10: Preparation of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB / PHBH) Cast Film on a Polyethylene Substrate, Using Methanol to Perform Non-Solvent Induced Phase Separation

[0186] Using a 254 μm thick draw bar, coat the P3HB / PHBH solution mixture prepared in Example 3 onto a porous ultra-high molecular weight polyethylene (UHMWPE) tape with a thickness of 185 μm and a porosity of 25% (prepared according to U.S. Patent No. 10,577,468 attributed to Sbriglia). Immediately immerse the P3HB / PHBH-coated PE tape in a bath filled with methanol (VWR International, LLC) at room temperature (about 22 °C) for 10 minutes to ensure solvent exchange. Remove the solvent-exchanged P3HB / PHBH-coated PE tape from the methanol bath and air dry it at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0187] Example 11: Preparation of Uniaxially Expanded Poly(3-hydroxybutyrate) Film

[0188] Use the P3HB / PTFE tape prepared according to Example 5 as the starting material for preparing a uniaxially expanded P3HB film. Using a razor blade, cut a rectangular sample (120 mm long, 10 mm wide) from the P3HB / PTFE tape and confine the sample between two pneumatic clamps with a gauge length of 80 mm ( Model 5965 tensile tester, equipped with an in-built convection oven, Illinois ToolWorks Inc, Norwood, Massachusetts). Equilibrate the sample at 110 °C for 1 minute and then uniaxially expand it to 4 times its original length. The uniaxially expanded P3HB film shows a porous nodular, fibrillar microstructure (see Figure 1A and 1B ). The properties of the uniaxially expanded P3HB film are provided in Table 2.

[0189] Example 12: Preparation of Uniaxially Expanded Poly(3-hydroxybutyrate) Film

[0190] Use the P3HB / PE tape prepared according to Example 6 as the starting material. Cut a rectangular sample (70 mm wide and 150 mm long) from the P3HB / PE tape. Load the rectangular sample into a Karo IV biaxial stretching machine (Brückner Maschinenbau GmbH & Co., Siegsdorf, Germany) and thermally equilibrate it at 120 °C for 2 minutes. Uniaxially stretch the rectangular sample to 9 times its original length at a strain rate of 100% / s. SEM micrographs of the uniaxially stretched sample show the formation of a porous P3HB film with a nodular and fibrillar microstructure (see Figure 2A and 2B ). The properties of the uniaxially stretched P3HB film are provided in Table 2.

[0191] Example 13: Preparation of Biaxially Expanded Poly(3-hydroxybutyrate) Film

[0192] Prepare a poly(3-hydroxybutyrate)-coated polyethylene tape (P3HB / PE) according to Example 6. Cut a rectangular sample (70 mm wide (transverse direction; TD), 150 mm long (machine direction; MD)) from the P3HB / PE tape. Load the rectangular sample into a Karo IV biaxial stretching machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrate it at 120 °C for 2 minutes. After equilibration at 120 °C for 2 minutes, biaxially stretch the rectangular sample (simultaneously in the MD and TD directions) at a strain of 100% / s in both directions (MD & TD) until its total area ratio reaches 8. Remove the biaxially stretched P3HB film from the PE substrate. The specific surface area of the P3HB film is measured to be 72.03 m 2 / g. Additional properties of the biaxially stretched P3HB film are shown in Table 2.

[0193] Example 14: Preparation of Biaxially Expanded Poly(3-hydroxybutyrate) Film

[0194] Prepare a poly(3-hydroxybutyrate)-coated polyethylene tape (P3HB / PE) according to Example 6. Cut a rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) from the P3HB / PE tape. Load the rectangular sample into a Karo IV biaxial stretching machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrate it at 120 °C for 2 minutes. Biaxially stretch the rectangular sample (simultaneously) at a strain rate of 100% / s in both MD and TD until its area ratio reaches 12. Remove the biaxially stretched P3HB film from the PE substrate. SEM micrographs of the biaxially stretched film show a porous nodular and fibrillar microstructure ( Figure 3A and 3B)。Differential scanning calorimetry (DSC) was performed on the P3HB cast film (before biaxial expansion) and the biaxially expanded P3HB film Figure 4 )。As Figure 4 shown, due to the presence of extended chain crystals within the fibrils, the melting peak of the biaxially expanded P3HB film is higher. Tensile testing was performed, and the matrix tensile strength (MTS) of the porous biaxially expanded P3HB film in both the MD and TD directions was 28.2 MPa. The biaxially expanded P3HB film was 50 μm thick, and the calculated porosity was 93.6%. Additional properties of the biaxially expanded P3HB film are shown in Table 2.

[0195] Example 15: Preparation of Biaxially Expanded Poly(3-hydroxybutyrate) Film

[0196] A poly(3-hydroxybutyrate)-coated polyethylene tape (P3HB / PE) was prepared according to Example 7. A rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) was cut from the P3HB / PE tape. The rectangular sample was loaded into a Karo IV biaxial expansion machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrated at 120 °C for 2 minutes. The rectangular sample was biaxially expanded (simultaneously) at a strain of 100% / s in both the MD and TD until its area ratio reached 30. The biaxially expanded P3HB film was removed from the PE substrate. The calculated porosity of the biaxially expanded P3HB film was 96%. Measured by the ATEQ air flow through the film was 161 L / hr. SEM micrographs of the simultaneously biaxially expanded P3HB film showed a porous microstructure containing knots and fibrils ( Figure 5A and 5B ). Properties of the biaxially expanded P3HB film are provided in Table 2.

[0197] Example 16: Preparation of Biaxially Expanded Poly(3-hydroxybutyrate) Film

[0198] A poly(3-hydroxybutyrate)-coated polyethylene tape (P3HB / PE) was prepared according to Example 6. A rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) was cut from the P3HB / PE tape. The rectangular sample was loaded into a Karo IV biaxial expansion machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrated at 140 °C for 2 minutes. The rectangular sample was biaxially expanded (simultaneously) at a strain of 100% / s in both the MD and TD until its area ratio reached 4. The biaxially expanded P3HB film was removed from the PE substrate. SEM micrographs of the biaxially expanded P3HB film showed a porous microstructure containing knots and fibrils ( Figure 6A and 6B)。The properties of the biaxially expanded P3HB film are provided in Table 2.

[0199] Example 17: Preparation of Biaxially Expanded Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Film

[0200] According to Example 8, a polyethylene tape (PHBV / PE) coated with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was prepared. A rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) was cut from the PHBV / PE tape. The rectangular sample was loaded into a Karo IV biaxial expansion machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrated at 120 °C for 2 minutes. The rectangular sample was biaxially expanded (simultaneously in the MD and TD) at strain rates of MD 100% / s and TD 10% / s until its area ratio reached 16. The biaxially expanded PHBV film was removed from the PE substrate. SEM micrographs of the biaxially expanded PHBV film showed a porous microstructure containing knots and fibrils ( Figure 7A and 7B ). Differential scanning calorimetry (DSC) was performed on the PHBV cast film (before biaxial expansion) and the biaxially expanded PHBV film ( Figure 8 ). As shown in Figure 8 , the melting peak of the biaxially expanded PHBV film was higher due to the presence of extended-chain crystals within the fibrils. The porosity of the biaxially expanded PHBV film calculated was 94%. Measured by ATEQ air flow through the film was 321 L / hr. Additional properties of the biaxially expanded PHBV film are shown in Table 2.

[0201] Example 18: Preparation of Sequentially Expanded PHBV Film

[0202] According to Example 8, a polyethylene tape coated with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) (PHBV / PE) was prepared. A rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) was cut from the PHBV / PE tape. The rectangular sample was loaded into a Karo IV biaxial stretching machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrated at 120 °C for 2 minutes. First, the rectangular sample was stretched four times its original length in the MD at a strain rate of 10% / s, and subsequently stretched in the TD at 100% / s until its total area ratio reached 16. The biaxially stretched PHBV film was removed from the PE substrate. The thickness of the individual biaxially stretched PHBV film was 26 μm, and the calculated porosity was 93.8%. The ATEQ air flow through the biaxially stretched PHBV film was 313 L / hr, and the water entry pressure (WEP) was 6.89 kPa. Additional properties of the biaxially stretched PHBV film are shown in Table 2.

[0203] Example 19: Preparation of Biaxially Expanded Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Film, Using Polyethylene Glycol as a Pore-Forming Agent

[0204] According to Example 9 (wherein the polyethylene glycol pore former had been removed previously), a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) tape was prepared. A rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) was cut from the PHBV tape. The rectangular sample was loaded into a Karo IV biaxial stretching machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrated at 120 °C for 2 minutes. The rectangular sample was biaxially stretched (simultaneously) at a strain rate of 100% / s in both the MD and TD until the area ratio reached 4. The biaxially stretched PHBV film was removed from the PE substrate. SEM micrographs of the biaxially stretched PHBV film showed a porous structure containing knots and fibrils ( Figure 9 ). The biaxially stretched PHBV film was 20 μm thick, and the calculated porosity was 68%. Additional properties of the biaxially stretched PHBV film are shown in Table 2.

[0205] Example 20: Preparation of Uniaxially Expanded P3HB / PHBH Film

[0206] According to Example 10, a polyethylene tape coated with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB / PHBH) was prepared. Using a razor blade, a rectangular sample 120 mm long and 10 mm wide was cut from the P3HB / PHBH tape. The rectangular sample was clamped between two pneumatic grips with a gauge length of 80 mm ( Model 5965 tensile tester, equipped with an internal convection oven, Illinois Tool Works Inc, Norwood, Massachusetts). The samples were equilibrated at 120 °C for 1 minute and then uniaxially expanded to 5 times their original length. The uniaxially expanded P3HB / PHBH films showed a porous microstructure containing knots and fibrils( Figure 10 ). Additional properties of the biaxially expanded P3HB / PHBH films are shown in Table 2.

[0207] Example 21: Preparation of Densified Poly(3-hydroxybutyrate) Film from Expanded P3HB Film

[0208] The biaxially expanded P3HB film prepared according to Example 14 was laminated between two polyimide films( DuPont, Wilmington, Delaware) and densified between two silicone rollers set at 120 °C. The compression force was set to 400 N / mm and the linear speed was set to 1 m / min. The resulting densified product had a thickness of 12 μm and a mass / area (MPA) of 3.67 g / m 2 . The properties of the densified P3HB film are provided in Table 2.

[0209] Example 22: Preparation of biaxially expanded poly(3-hydroxybutyrate) / polyethylene composite (P3HB / PE)

[0210] According to Example 7, a poly(3-hydroxybutyrate) / polyethylene (P3HB / PE) composite tape was prepared. A rectangular sample 70 mm wide (MD) and 150 mm long (TD) was cut from the P3HB / PE composite tape. The rectangular sample was loaded into a Karo IV biaxial expansion machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrated at 120 °C for 2 minutes. The rectangular sample was biaxially expanded (simultaneously) at a strain of 100% / s in both the MD and TD until the area ratio reached 4. SEM micrographs of the biaxially expanded P3HB / PE composite showed a porous microstructure with knots and fibrils( Figure 11A and 11B ). Figure 11 is a top view of an AP3HB / PE composite showing the knot and fibril microstructure of the P3HB layer. Figure 11B is a cross-sectional view showing the microstructure of the laminated porous P3HB / PE composite.

[0211] Comparative Example 23: Preparation of uniaxially stretched dense poly(3-hydroxybutyrate) film without the assistance of a stretchable substrate

[0212] Using a 254-μm draw bar, coat the solution prepared as described in Example 1 on a glass plate. Subsequently, cover the P3HB-coated glass with a glass lid and slowly evaporate the chloroform solvent at room temperature (about 22 °C) for 24 hours to obtain a dense P3HB film. Using a razor blade, cut a rectangular sample (120 mm long and 10 mm wide) from the dense P3HB film and confine the sample between two pneumatic clamps with a gauge length of 80 mm ( Model 5965 tensile tester, equipped with a built-in convection oven, Illinois Tool Works Inc, Norwood, Massachusetts). Equilibrate the confined dense P3HB film at 100 °C for 1 minute and then uniaxially stretch it at a rate of 100% / s until a 25% strain is achieved. The dense P3HB film cannot be stretched beyond 25% because macroscopic defects form after this strain, indicating that a porous P3HB film-like material with a knot and fibril microstructure cannot be formed.

[0213] Comparative Example 24: Uniaxial expansion of dense poly(3-hydroxybutyrate-co-3-hydroxyvalerate) film

[0214] A dense poly(3-hydroxybutyrate-co-3-hydroxyvalerate) film (10 μm thick) was obtained from Goodfellow Corporation (Pittsburgh, Pennsylvania). Cut the dense PHBV film into rectangles (120 mm long and 10 mm wide). Confine a rectangular dense PHBV film sample between two pneumatic clamps with a gauge length of 80 mm ( Model 5965 tensile tester, equipped with a built-in convection oven, Illinois ToolWorks Inc, Norwood, Massachusetts). Equilibrate the dense PHBV film sample at 120 °C for 1 minute and then uniaxially expand it at a rate of 100% / s to twice its original length. However, the PHBV sample is brittle and a porous PHBV film-like material with a knot and fibril microstructure cannot be formed.

[0215] Comparative Example 25: Uniaxially expanded laminated composite of porous PTFE tape and dense PHVB film

[0216] A porous PTFE tape (258 μm thick, 28% porosity) was fabricated according to the method of U.S. Patent No. 3,953,566 assigned to Gore and cut using a razor blade. A dense 10-μm-thick poly(3-hydroxybutyrate-co-3-hydroxyvalerate) film (obtained from Goodfellow Corporation, Pittsburgh, Pennsylvania) was also cut into the same size and laminated on top of the porous PTFE tape. The laminated materials were sandwiched between two thinned PTFE films (non-porous; using a release liner) and a metal sheet. The sandwiched materials were placed in a hydraulic press (Carver, Inc., Wabash, IN) and thermally equilibrated at 175 °C for 2 minutes. The thermally equilibrated stacked materials were compressed at 500 lbs (about 3.45 MPa) for 30 seconds. The thinned PTFE films and the metal sheet were removed to obtain a laminated PHVB / PTFE composite material. A 120-mm long and 10-mm wide rectangular sample was cut from the laminated PHVB / PTFE composite using a razor blade and then clamped between two pneumatic fixtures with a gauge length of 80 mm( 5965 tensile tester, equipped with a built-in convection oven, Illinois ToolWorks Inc, Norwood, Massachusetts). The laminated PHVB / PTFE composite was equilibrated at 120 °C for 1 minute and then uniaxially expanded at a rate of 100% / s to twice its original length. However, the PHBV layer ruptured and a porous PHBV film with a nodular and fibrillar microstructure was not obtained.

[0217] Table 2

[0218] Sample properties

[0219]

[0220]

[0221] Example 26: Preparation of poly(3-hydroxy-2,2-dimethylbutyrate) (P3H(Me)2B) solution

[0222] Poly(3-hydroxy-2,2-dimethylbutyrate) (P3H(Me)2B) was synthesized according to the method described by Zhou et al. in “Chemically circular, mechanically tough, and melt-processable polyhydroxyalkanoates”, Science (2023) 380, 64 - 69. 0.68 g of the P3H(Me)2B polymer was dried at room temperature (about 22 °C) and under vacuum for 24 hours. Subsequently, in a glass vial with a polytetrafluoroethylene (PTFE) stir bar, the P3H(Me)2B polymer was dissolved in 5 mL of chloroform (Sigma Aldrich, St. Louis, Missouri) at 70 °C for 6 hours. The resulting solution was aged at room temperature (about 22 °C) for 24 hours.

[0223] Example 27: Preparation of poly(3-hydroxy-2,2-diethylbutyrate) (P3H(Et)2B) solution

[0224] P3H(Et)2B was synthesized according to the method described by Zhou et al. (see above). 10 g of the P3H(Et)2B polymer was dried at room temperature (about 22 °C) and under vacuum for 24 hours. Subsequently, in a jacketed glass reactor with a polytetrafluoroethylene (PTFE) stir paddle, the P3H(Et)2B polymer was dissolved in 100 mL of chloroform (Sigma Aldrich, St. Louis, Missouri) at 75 °C under reflux conditions for 1 hour. The resulting solution was aged at room temperature (about 22 °C) for 24 hours.

[0225] Example 28: Preparation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) solution

[0226] Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) was synthesized according to the method described by Hori et al. in “Chemical synthesis of high molecular weight poly(3-hydroxybutyrate-co-3-hydroxybutyrate)”, Polymer (1995) 36(24) 4703 - 4705. 10 g of the P3HB4HB polymer was dried at room temperature (about 22 °C) and under vacuum for 24 hours. Subsequently, in a jacketed glass reactor with a polytetrafluoroethylene (PTFE) stir paddle, the P3HB4HB polymer was dissolved in 100 mL of chloroform (Sigma Aldrich, St. Louis, Missouri) at 75 °C under reflux conditions for 1 hour. The resulting solution was aged at room temperature (about 22 °C) for 24 hours.

[0227] Example 29: Preparation of a cast tape of poly(3-hydroxy-2,2-dimethylbutyrate) (P3H (Me)2B) on a polytetrafluoroethylene (PTFE) substrate, using methanol for poor solvent-induced phase separation (NIPS)

[0228] According to the method of U.S. Patent No. 3,953,566 attributed to Gore, a porous PTFE tape (with a thickness of 258 μm and a porosity of 28%) was prepared. The porous PTFE tape was attached to a glass plate, and then coated with the P3H(Me)2B solution (15 mL) described in Example 25 using a 254-μm draw bar. Subsequently, the P3H(Me)2B-coated PTFE tape was immediately transferred to a bath filled with methanol (VWR International, LLC, Radnor, Pennsylvania) at room temperature (about 22°C) for poor-solvent-induced phase separation. The P3H(Me)2B-coated PTFE tape was kept in the methanol bath for at least 5 minutes until the solvent exchange was completed. The solvent-exchanged P3H(Me)2B / PTFE tape was removed from the bath and air-dried at room temperature (about 22°C) for 24 hours to remove the excess solvent.

[0229] Example 30: Preparation of a cast tape of poly(3-hydroxy-2,2-dimethylbutyrate) (P3H(Me)2B) on a polyethylene (PE) substrate, using methanol for poor solvent-induced phase separation (NIPS)

[0230] Using a 304.8-μm draw bar, the P3H(Me)2B solution (5 mL) prepared as described in Example 26 was coated on a porous ultra-high molecular weight polyethylene (PE) tape (with a thickness of 185 μm and a porosity of 25%, prepared according to the method described in U.S. Patent No. 10,577,468 attributed to Sbriglia). The P3H(Me)2B-coated PE tape was immediately immersed in a bath filled with methanol (VWR International, LLC) at room temperature (about 22°C) for poor-solvent-induced phase separation. The P3H(Me)2B-coated PE tape was kept in the methanol bath for 5 minutes until the solvent exchange was completed. The solvent-exchanged P3H(Me)2B / PE tape was removed from the bath and air-dried at room temperature (about 22°C) for 24 hours to remove the excess solvent.

[0231] Example 31: Preparation of a cast tape of poly(3-hydroxy-2,2-diethylbutyrate) (P3H (Et)2B) on a polytetrafluoroethylene (PTFE) substrate, using methanol for poor solvent-induced phase separation (NIPS)

[0232] According to the method of U.S. Patent No. 3,953,566 owned by Gore, a porous PTFE tape (with a thickness of 258 μm and a porosity of 28%) was prepared. The porous PTFE tape was attached to a glass plate, and then coated with the P3H(Et)2B solution (15 mL) described in Example 27 using a 254-μm drawdown bar. Subsequently, the P3H(Et)2B-coated PTFE tape was immediately transferred to a bath filled with methanol (VWR International, LLC, Radnor, Pennsylvania) at room temperature (about 22 °C) for poor-solvent-induced phase separation. The P3H(Et)2B-coated PTFE tape was kept in the methanol bath for at least 5 minutes until the solvent exchange was completed. The solvent-exchanged P3H(Et)2B / PTFE tape was removed from the bath and air-dried at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0233] Example 32: Preparation of a cast tape of poly(3-hydroxy-2,2-diethylbutyrate) (P3H(Et)2B) on a polyethylene (PE) substrate, using methanol for poor solvent-induced phase separation (NIPS)

[0234] Using a 254-μm drawdown bar, the P3H(Et)2B solution (5 mL) prepared as described in Example 27 was coated on a porous ultra-high molecular weight polyethylene (PE) tape (with a thickness of 185 μm and a porosity of 25%, prepared according to the method described in U.S. Patent No. 10,577,468 owned by Sbriglia). The P3H(Et)2B-coated PE tape was immediately immersed in a bath filled with methanol (VWR International, LLC) at room temperature (about 22 °C) for poor-solvent-induced phase separation. The P3H(Et)2B-coated PE tape was kept in the methanol bath for 5 minutes until the solvent exchange was completed. The solvent-exchanged P3H(Et)2B / PE tape was removed from the bath and air-dried at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0235] Example 33: Preparation of a cast tape of poly(3-hydroxybutyrate-co-4-hydroxybutyric acid) (P3HB4HB) on a polytetrafluoroethylene (PTFE) substrate, using methanol for poor solvent-induced phase separation (NIPS)

[0236] According to the method of U.S. Patent No. 3,953,566 attributed to Gore, a porous PTFE tape (with a thickness of 258 μm and a porosity of 28%) was prepared. The porous PTFE tape was attached to a glass plate, and then coated with a P3HB4HB solution (15 mL) prepared as described in Example 28 using a 254-μm drawdown bar. Subsequently, the P3HB4HB-coated PTFE tape was immediately transferred to a bath filled with methanol (VWR International, LLC, Radnor, Pennsylvania) at room temperature (about 22 °C) for poor-solvent-induced phase separation. The P3HB4HB-coated PTFE tape was kept in the methanol bath for at least 5 minutes until the solvent exchange was complete. The solvent-exchanged P3HB4HB / PTFE tape was removed from the bath and air-dried at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0237] Example 34: Preparation of a cast tape of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) on a polyethylene (PE) substrate, using methanol for poor solvent-induced phase separation (NIPS)

[0238] Using a 254-μm drawdown bar, a porous ultra-high molecular weight polyethylene (PE) tape (with a thickness of 185 μm and a porosity of 25%, prepared according to the method described in U.S. Patent No. 10,577,468 attributed to Sbriglia) was coated with a P3HB4HB solution (5 mL) prepared as described in Example 28. The P3HB4HB-coated PE tape was immediately immersed in a bath filled with methanol (VWR International, LLC) at room temperature (about 22 °C) for poor-solvent-induced phase separation. The P3HB4HB-coated PE tape was kept in the methanol bath for 5 minutes until the solvent exchange was complete. The solvent-exchanged P3HB4HB / PE tape was removed from the bath and air-dried at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0239] Example 35: Preparation of uniaxially expanded poly(3-hydroxy-2,2-dimethylbutyrate) ( P3H(Me)2B) film

[0240] Using the P3H(Me)2B / PE tape prepared according to Example 30 as the starting material. A rectangular sample (12.5 mm wide and 75.4 mm long) was cut from the P3H(Me)2B / PE tape. The rectangular sample was loaded between two pneumatic clamps with a gauge length of 30 mm ( 5965 tensile tester, equipped with a built-in convection oven, Illinois Tool Works Inc, Norwood, Massachusetts), and thermally equilibrated at 120 °C for 2 minutes. Subsequently, the rectangular sample was uniaxially expanded to 1.4 times its original length at a strain rate of 10% / s. This process produced a uniaxially expanded porous P3H(Me)2B film with a knot and fibril microstructure.

[0241] Example 36: Preparation of uniaxially expanded poly(3-hydroxy-2,2-diethylbutyrate) film

[0242] Use the P3H(Et)2B / PE tape prepared according to Example 32 as the starting material. Cut a rectangular sample (70 mm wide and 150 mm long) from the P3H(Et)2B / PE tape. Load the rectangular sample into a Karo IV biaxial stretching machine (Brückner Maschinenbau GmbH & Co., Siegsdorf, Germany) and thermally equilibrate it at 120 °C for 2 minutes. Uniaxially stretch the rectangular sample at a strain rate of 10% / s to 4 times its original length. Remove the uniaxially stretched P3H(Et)2B film from the PE substrate. This process should produce a uniaxially stretched porous P3H(Et)2B film with a knot and fibril microstructure.

[0243] Example 37: Preparation of uniaxially expanded poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) film

[0244] Use the P3HB4HB / PE tape prepared according to Example 34 as the starting material. Cut a rectangular sample (70 mm wide and 150 mm long) from the P3HB4HB / PE tape. Load the rectangular sample into a Karo IV biaxial stretching machine (Brückner Maschinenbau GmbH & Co., Siegsdorf, Germany) and thermally equilibrate it at 120 °C for 2 minutes. Uniaxially stretch the rectangular sample at a strain rate of 10% / s to 4 times its original length. Remove the uniaxially stretched P3HB4HB film from the PE substrate. This process should produce a uniaxially stretched porous P3HB4HB film with a knot and fibril microstructure.

[0245] Example 38: Preparation of biaxially expanded poly(3-hydroxy-2,2-dimethylbutyrate) (P3H(Me)2B) film

[0246] Prepare a P3H(Me)2B-coated polyethylene tape (P3H(Me)2B / PTFE) according to Example 29. Cut a rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) from the P3H(Me)2B / PTFE tape. Load the rectangular sample into a Karo IV biaxial stretching machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrate it at 120 °C for 2 minutes. Biaxially stretch (simultaneously) the rectangular sample at a strain of 100% / s in both the MD and TD until the area ratio reaches 4. This process should produce a biaxially stretched porous P3H(Me)2B film containing knots and fibrils.

[0247] Example 39: Preparation of biaxially expanded poly(3-hydroxy-2,2-diethylbutyrate) (P3H(Et)2B) film

[0248] Prepare a P3H(Et)2B-coated polyethylene tape (P3H(Et)2B / PTFE) according to Example 31. Cut a rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) from the P3H(Et)2B / PTFE tape.

[0249] Load the rectangular sample into a Karo IV biaxial inflation machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrate it at 120 °C for 2 minutes.

[0250] Biaxially inflate the rectangular sample (simultaneously) at a strain of 100% / s in both the MD and TD until the area ratio reaches 4. This process should produce a biaxially inflated P3H(Et)2B porous film containing knots and fibrils.

[0251] Example 40: Preparation of biaxially expanded poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) film

[0252] Prepare a P3HB4HB-coated polyethylene tape (P3HB4HB / PTFE) according to Example 33. Cut a rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) from the P3HB4HB / PTFE tape. Load the rectangular sample into a Karo IV biaxial inflation machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrate it at 120 °C for 2 minutes. Biaxially inflate the rectangular sample (simultaneously) at a strain of 100% / s in both the MD and TD until the area ratio reaches 4. This process should produce a biaxially inflated P3HB4HB porous film containing knots and fibrils.

[0253] Example 41: Preparation of a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) solution.

[0254] Dry 10 g of P3HB4HB polymer (Helian Polymers, Belfeld, Netherlands) under vacuum at room temperature (about 22 °C) for 24 hours. Subsequently, dissolve the P3HB4HB polymer in 100 mL of chloroform (Sigma Aldrich, St. Louis, Missouri) at 75 °C under reflux conditions in a jacketed glass reactor with a polytetrafluoroethylene (PTFE) stirrer paddle for 4 hours. Age the resulting solution at room temperature (about 22 °C) for 24 hours.

[0255] Example 42: Preparation of a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) casting tape on a polyethylene (PE) substrate, using methanol for poor solvent-induced phase separation (NIPS)

[0256] Using a 304.8 μm draw bar, coat the porous ultra-high molecular weight polyethylene (UHMWPE) tape with a thickness of 360 μm and a porosity of 26% (prepared according to U.S. Patent No. 10,577,468 attributed to Sbriglia) with the P3HB4HB solution prepared in Example 41. Immediately immerse the P3HB4HB-coated PE tape in a bath filled with methanol (VWR International, LLC) at room temperature (about 22 °C) for poor solvent-induced phase separation. Keep the P3HB4HB-coated PE tape in the methanol bath for 10 minutes until the solvent exchange is complete. Remove the solvent-exchanged P3HB4HB / PE tape from the bath and air dry it at room temperature (about 22 °C) for 24 hours to remove the excess solvent.

[0257] Example 43: Preparation of a uniaxially expanded poly(3-hydroxybutyrate-co-4-hydroxybutyrate) film

[0258] Use the P3H4HB / PE tape prepared according to Example 42 as the starting material. Cut a rectangular sample (25.4 mm wide and 75.4 mm long) from the P3H4HB / PE tape. Load the rectangular sample between two pneumatic clamps with a gauge length of 30 mm ( 5965 tensile tester, equipped with a built-in convection oven, Illinois Tool Works Inc, Norwood, Massachusetts), and thermally equilibrate at 60 °C for 2 minutes. Subsequently, uniaxially expand the rectangular sample at a strain rate of 10% / s to 1.4 times its original length. This process produces a uniaxially expanded porous P3H4HB film with a knot and fibril microstructure.

[0259] Example 44: Preparation of poly(3-hydroxybutyrate) (P3HB) monofilaments

[0260] Prepare a poly(3-hydroxybutyrate)-coated polyethylene tape (P3HB / PE) according to Example 6. Cut a rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) from the P3HB / PE tape. Load the rectangular sample into a Karo IV biaxial expansion machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrate at 120 °C for 2 minutes. Biaxially expand (simultaneously) the rectangular sample at a strain of 100% / s in both the MD and TD until the area ratio reaches 9. Remove the biaxially expanded P3HB film from the PE substrate. Subsequently, cut the film to produce monofilaments 1.7 mm wide and 35 μm thick, which have a knot and fibril microstructure.

[0261] Example 45: Preparation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) monofilaments

[0262] According to Example 8, a polyethylene tape coated with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) (PHBV / PE) was prepared. A rectangular sample 70 mm wide (transverse direction; TD) and 150 mm long (machine direction; MD) was cut from the PHBV / PE tape. The rectangular sample was loaded into a Karo IV biaxial inflation machine (Brückner Maschinenbau GmbH & Co.) and thermally equilibrated at 120 °C for 2 minutes. The rectangular sample was biaxially inflated (simultaneously) at a strain of 100% / s in both the MD and TD until the area ratio reached 4. The biaxially inflated PHBV film was removed from the PE substrate. The film was then slit to produce monofilaments 1.5 mm wide and 36 μm thick, which had a knot and fibril microstructure. The porosity of the monofilaments was 84.7%.

[0263] The disclosure of the present application has been described generally and in connection with specific embodiments above. It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the invention. Accordingly, the embodiments are intended to cover such modifications and variations of the invention as fall within the scope of the appended claims and their equivalents.

Claims

1. A method, the method comprising: At a deposition temperature below the melting temperature (T m ) of the PHA polymer, a partially crystalline polyhydroxyalkanoate (PHA) polymer is deposited on a substrate; and At a temperature between the glass transition temperature (T g ) of the PHA polymer and the melting temperature (T m ) of the PHA polymer, the PHA-substrate composite is expanded to form a porous expanded PHA composite, the porous expanded PHA composite comprising a porous PHA material and having a microstructure comprising the following: a plurality of knots; and a plurality of fibrils, the plurality of fibrils being interconnected with the plurality of knots, each of the fibrils defining a fibril axis.

2. The method according to claim 1, wherein the fibril comprises extended chain crystals of the PHA polymer oriented along the fibril axis, and wherein the melting temperature of the extended chain crystals of the PHA polymer is higher than the T of the PHA polymer before expansion m .

3. The method according to claim 1 or claim 2, wherein depositing a partially crystalline PHA polymer comprises: dissolving the PHA polymer in a solvent to form a PHA solution; casting the PHA solution onto the substrate; and at least partially crystallizing the PHA polymer by partially removing the solvent, adjusting the deposition temperature, or a combination thereof.

4. The method according to any one of claims 1 to 3, the method further comprising: separating the porous PHA material from the porous expanded PHA composite to form a self-supporting porous PHA material.

5. The method according to any one of claims 1 to 4, wherein the porosity of the self-supporting porous PHA material is from 25% to 99%.

6. The method according to any one of claims 1 to 5, wherein the self-supporting porous PHA material is in the form of a film, a tube, a sheet, or a three-dimensional shape.

7. The method according to any one of claims 1 to 6, wherein the matrix tensile strength of the self-supporting porous PHA material in the machine direction (MD) and / or the transverse direction (TD) is at least 5 MPa.

8. The method according to any one of claims 1 to 7, wherein the self-supporting porous PHA material has a total surface area of 20 m 2 / g to 80 m 2 / g.

9. The method according to any one of claims 1 to 8, wherein the PHA-substrate composite is expanded at a temperature below the T m of the PHA polymer by 10 °C or less.

10. The method according to any one of claims 1 to 9, wherein the PHA-substrate composite is uniaxially expanded, biaxially expanded, or radially expanded.

11. The method according to any one of claims 1 to 10, wherein the PHA-substrate composite expands at a rate of 1% / s to 1000% / s.

12. The method according to any one of claims 1 to 11, wherein the expansion ratio of the PHA-substrate composite is from 1:1.1 to 1:

100.

13. The method according to any one of claims 1 to 12, wherein the PHA polymer comprises a monomer, a homopolymer, or a copolymer, the monomer, homopolymer, or copolymer comprising 3-hydroxybutyrate, 3-hydroxyvalerate, 4-hydroxybutyrate, 3-hydroxyhexanoate, or any combination thereof.

14. The method according to any one of claims 1 to 13, wherein the PHA polymer is: poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(4-hydroxybutyrate) (P4HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), or poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx).

15. The method according to any one of claims 1 to 14, the method further comprising: forming a modified PHA article by processing the porous expanded PHA composite or the self-supporting porous PHA material, wherein the processing includes: coating, liquid absorption, lamination, or any combination thereof, and wherein the modified PHA article is porous or non-porous.

16. The method according to any one of claims 1 to 15, the method further comprising: densifying the porous expanded PHA composite, the porous self-supporting porous PHA material, or the modified PHA article to form a densified PHA material.

17. The method according to claim 16, wherein the densified PHA material is detectable of an endotherm associated with the presence of the extended-chain crystals of the PHA polymer.

18. The method according to claim 16 or claim 17, wherein the densifying includes applying heat, applying pressure, stretching, or any combination thereof.

19. The method according to any one of claims 1-16, wherein prior to deposition on a substrate, the PHA polymer further comprises at least one pore-forming agent.

20. The method according to claim 19, the method further comprising removing the pore-forming agent before or after expanding the PHA-substrate composite.

21. The method according to any one of claims 1-16, wherein the substrate is a deformable substrate.

22. The method according to claim 21, wherein the deformable substrate is an expandable polymer.

23. The method according to claim 21 or claim 22, wherein the deformable substrate comprises a material selected from the group consisting of: polytetrafluoroethylene (PTFE) tape, PTFE film, polyolefin tape, polyolefin film, expanded polyolefin film, ultra-high molecular weight polyethylene (UHMWPE) tape, UHMWPE film, and expanded UHMWPE film.

24. A porous polyhydroxyalkanoate (PHA) material formed from a PHA polymer, the porous PHA material having a microstructure comprising: a plurality of knots; and a plurality of fibrils interconnected with the plurality of knots, the plurality of fibrils defining a fibril axis.

25. The porous PHA material according to claim 24, wherein the fibril comprises a plurality of extended-chain crystals of the PHA polymer oriented along the fibril axis, and wherein the melting temperature of the extended-chain crystals of the PHA polymer is higher than the T of the PHA polymer before expansion m .

26. The porous PHA material according to claim 24 or claim 25, wherein the molecular weight of the PHA polymer is from 30,000 g / mol to 10,000,000 g / mol.

27. The porous PHA material according to any one of claims 24-26, wherein the porosity of the porous PHA material is from 25% to 99%.

28. The porous PHA material according to any one of claims 24-27, wherein the porous PHA material is in the form of a film, a tube, a sheet, or a three-dimensional shape.

29. The porous PHA material according to any one of claims 24-28, wherein the matrix tensile strength of the porous PHA material in the machine direction (MD) and / or the transverse direction (TD) is at least 5 MPa.

30. The porous PHA material according to any one of claims 24-29, wherein the total surface area of the porous PHA material per unit mass is greater than 20 m 2 / g.

31. The porous PHA material according to any one of claims 24-30, wherein the PHA polymer comprises a monomer, a homopolymer, or a copolymer, the monomer, the homopolymer, or the copolymer comprising 3-hydroxybutyrate, 3-hydroxypentanoate, 4-hydroxybutyrate, 3-hydroxyhexanoate, or any combination thereof.

32. The porous PHA material according to any one of claims 24 - 31, wherein the PHA polymer is: poly(3 - hydroxybutyrate) (PHB), poly(3 - hydroxybutyrate - co - 3 - hydroxyvalerate) (PHBV), poly(4 - hydroxybutyrate) (P4HB), poly(3 - hydroxybutyrate - co - 4 - hydroxybutyrate), or poly(3 - hydroxybutyrate - co - hydroxyhexanoate) P(HB - co - HHx).

33. The porous PHA material according to any one of claims 24 - 32, wherein the PHA polymer is blended with an additional polymer selected from: polylactic acid (PLA), poly(butylene adipate terephthalate) (PBAT), poly(butylene succinate) (PBS), cellulose, poly(glycolic acid) (PGA), polycaprolactone (PCL), poly(vinyl acetate) (PVAc), chitin, chitosan, starch, and any combination thereof.

34. A composite, the composite comprising the porous PHA material according to any one of claims 24 - 33.

35. The composite according to claim 34, wherein the PHA composite is microporous.

36. An article, the article comprising the porous PHA material according to any one of claims 24 - 33, or the composite according to claim 34 or claim 35.

37. The article according to claim 36, wherein the article comprises a woven or non - woven support substrate.

38. A material, the material comprising densified expanded polyhydroxyalkanoate, which exhibits an endotherm associated with the presence of straight - chain crystals of the remaining PHA polymer, wherein the porosity of the material is less than 10%.

39. A porous polyhydroxyalkanoate (PHA) material, which is formed from a PHA polymer of formula I or formula II: or Formula II: wherein R1 and R2 are independently H, or a C1 - C6 alkyl or aryl group; R3 is a C1 - C4 alkyl group; X is 2 - 4; and n = 3000 to 100,000; and wherein the porous PHA material has a fibrillated microstructure comprising: a plurality of knots interconnected by fibrils, or only fibrils, the fibrils having an orientation defining a fibril axis.

40. The porous PHA material according to claim 39, wherein the fibril comprises a plurality of extended chain crystals of the PHA polymer oriented along the fibril axis, and wherein the melting temperature of the extended chain crystals of the PHA polymer is higher than the T of the PHA polymer before expansion m .

41. The porous PHA material according to claim 39 or claim 40, wherein the molecular weight of the PHA polymer is from 30,000 g / mol to 10,000,000 g / mol.

42. The porous PHA material according to any one of claims 39 - 41, wherein the porosity of the porous PHA material is from 25% to 99%.

43. The porous PHA material according to any one of claims 39 - 42, wherein the porous PHA material is in the form of a film, tube, sheet, monofilament, or three - dimensional shape.

44. The porous PHA material according to any one of claims 39 - 43, wherein the matrix tensile strength of the porous PHA material in the machine direction (MD) and / or the transverse direction (TD) is at least 5 MPa.

45. The porous PHA material according to any one of claims 39-44, wherein the total surface area of the porous PHA material per unit mass is greater than 20 m 2 / g.

46. The porous PHA material according to any one of claims 39-45, wherein the PHA polymer comprises a monomer, a homopolymer, or a copolymer, and the monomer, homopolymer, or copolymer comprises 3-hydroxybutyrate, 3-hydroxyvalerate, 4-hydroxybutyrate, 3-hydroxyhexanoate, 3-hydroxy-2,2-dimethylbutyrate, 3-hydroxy-2-methylbutyrate, 3-hydroxy-2-ethylbutyrate, 3-hydroxy-2-methyl-2-ethylbutyrate, 3-hydroxy-2,2-diethylbutyrate, or any combination thereof.

47. The porous PHA material according to any one of claims 39-46, wherein the PHA polymer is: poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(4-hydroxybutyrate) (P4HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-hydroxyhexanoate) P(HB-co-HHx), poly(3-hydroxy-2,2-dimethylbutyrate), poly(3-hydroxy-2-methylbutyrate), poly(3-hydroxy-2-ethylbutyrate), poly(3-hydroxy-2,2-diethylbutyrate), or poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

48. The porous PHA material according to any one of claims 39-47, wherein the PHA polymer is blended with an additional polymer selected from: polylactic acid (PLA), poly(butylene adipate terephthalate) (PBAT), poly(butylene succinate) (PBS), cellulose, poly(glycolic acid) (PGA), polycaprolactone (PCL), poly(vinyl acetate) (PVAc), chitin, chitosan, starch, and any combination thereof.

49. A composite, the composite comprising the porous PHA material according to any one of claims 39-48.

50. The composite according to claim 49, wherein the PHA composite is microporous.

51. An article, the article comprising the porous PHA material according to any one of claims 39-48, or the composite according to claim 49 or claim 50.

52. The article according to claim 51, the article being in the form of a film, a tube, a sheet, a monofilament article, or a three-dimensional shape.

53. The article according to claim 52, wherein the monofilament article is dental floss, a medical suture, or fishing line.

54. The article according to claim 51, wherein the article comprises a woven or non-woven support substrate.

55. A woven or knitted fabric comprising the porous PHA material according to any one of claims 39 to 48.

56. A wearable garment comprising the woven or knitted fabric according to claim 55.

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