High molecular weight functionalized polyolefins by slurry admet polymerization

Abstract

Disclosed herein are improved methods and materials for increasing efficiency of ADMET polymerization. One aspect of the disclosure involves a method of conducting ADMET polymerization in a slurry that applies vacuum at strategic times in the polymerization process to remove ethylene to realize the high conversions that lead to high molecular weights.

Description

Attorney Docket Nol: 10457-605US0High Molecular Weight Functionalized Polyolefins by Slurry ADMET PolymerizationBACKGROUND

[0001] ADMET polymerization involves polymerizing alpha-omega dienes via olefin metathesis, which releases ethylene gas. A metal-carbene catalyst (typically Ru-based) firstly coordinates to the terminal double bond of the olefin monomer to form a metal-substituted cyclobutane intermediate (FIG. 1), which then decompose to give a metal methylene complex by removing a molecule of alkene. The metal methylene complex enters the polymerization cycle and coordinates with the terminal double bond of another olefin monomer to form a new metal-substituted cyclobutane intermediate. After that, the intermediate releases a growing polymer chain and metal complex, which can further react with monomers. However, since olefin metathesis is reversible, the ADMET reaction is also capable of undesirable depolymerization, chain transfer, and cyclization.

[0002] ADMET produces functionalized polyolefins with superior mechanical and physical properties, including tensile strength, elasticity, and thermal stability. For instance, incorporating a variety of functionalities into polyethylene copolymers led to a range of Tms that span from -12 °C - 134 °C (Figure 2). These effects are primarily due to modifications to the crystalline or amorphous content of polyolefins, which in turn also impact their mechanical properties. This realization inspires the current study to produce novel polyethylene copolymers and explore their thermomechanical properties with the goal of uncovering structure-property relationships in these materials. Ultimately, understanding the structure-property relationships in functionalized polyolefins will enable a systematic investigation into the application relevance of these materials.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Figure 1 is a diagram showing an ADMET Polymerization reaction whereby ethylene gas is released.

[0004] Figure 2 is a graph showing melting points of polymers having different pendant functionalities.Attorney Docket Nol: 10457-605US0

[0005] Figure 3 is a diagram of general reaction scheme as one example of a method embodiment.

[0006] Figure 4 provides structures of example monomers that may be used in an ADMET polymerization method embodiment.

[0007] Figure 5 provides a general reactor setup and reaction scheme relating to a large scale stirred reactor for use with method embodiments described herein.

[0008] Figure. 6 shows a reaction scheme and setup using a round bottle.

[0009] Figure ? shows graphs of HNMR and GPC analysis was conducted on a 6C-NBoc Admet polymer (see FIG. 7A-C). FIG. 7B shows a graph of the GPC analysis. FIG. 7C shows the HNMR is a graph of the 'HNMR analysis.

[0010] Figure s shows graphs of TGA and DSC analysis was also conducted on the 6C-NBoc- AdMet polymer (see FIG. 8A-C). FIG. 8B shows a graph representing the TGA analysis. FIG. 8C shows a graph representing the DSC analysis.

[0011] Figure 9 shows graphs pertaining to Shear rheology analysis on 6C-NBoc-AdMet polymer this data shows that the high molecular weight materials are more resistant to deformation than their lower molecular weight analogues.

[0012] Figure 10 is a diagram showing a polymer with a Boc protected heteroatom modified post polymerization by saturation and deprotection of the Boc group, and examples of other hydrogenation strategies.

[0013] Figure 11 shows graphs pertaining to TGA and DSC analysis was also conducted on the 6C-NH-AdMet polymer (see FIG. 11A-C). FIG. 11B shows a graph representing the TGA analysis. FIG. 11C shows a graph representing the DSC analysis.

[0014] Figure 12 provides a diagram showing various classes of monomers and polymers formed using such monomers.DETAIEED DESCRIPTION

[0015] It has been realized that in view of the reversibility of ADMET reactions, it is critical to constantly remove ethylene to realize the high conversions that lead to high molecular weights. It is also crucial to remove oxygen and water from the reaction mixtures, which are known to inhibitAttorney Docket Nol: 10457-605US0 catalytic performance. Finally, the step-growth nature of ADMET polymerization requires that the monomers used must be extremely pure, because even small amounts of monofunctional diene or contaminant can greatly suppress the molecular weight.

[0016] Accordingly, it has been determined that there is a need for an improved ADMET process that avoids challenges associated with conventional techniques. Namely, high molecular weight heteroatom containing polyolefins are known to be challenging to produce via metathesis routes, supported organometallic polymerizations, or other C-C bond-forming reactions. Described herein are synthesis embodiments that circumvent these challenges by conducting a metathesis polymerization in a slurry, where the rates of polymerization are enhanced by the high concentrations of monomer in these mixtures. Moreover, these polymerizations are performed under vacuum, which entropically drives these polymerizations by the release of ethylene. This polymerization approach is amenable to the incorporation of heteroatoms precisely installed along the carbon-backbone. The methods described herein provide a route to a vast library of high molecular weight functionalized polyolefins that can be processed using commercially relevant methods (e.g. fiber spinning), which will enable the exploration of these materials in a variety of applications including structural materials, garments, and membranes. In certain examples, polymers with molecular weights of up to 50k g / mol, 100k g / mol and higher are achieved.

[0017] In one embodiment, provided is a method of conducting ADMET polymerization in a slurry, the method involving (a) mixing an amount of monomer and an amount of catalyst in a container under N2 protection to form a mixture; (b) heating the mixture while stirring such that polymerization occurs and ethylene is produced as a byproduct; (c) removing the ethylene from the container via vacuum; (d) adding an amount of dichlorobenzene to the container as solidity of the mixture increases, wherein addition of the dichlorobenzene reduces solidity of the mixture to create a slurry; (e) subsequent to step (d), and as solidity of the slurry increases, adding an additional amount of dichlorobenzene to reduce solidity of the slurry; and (f) repeating step (e) 1- 4 times to produce polymer; and optionally, wherein step (c) occurs continuously during steps (d), (e) and (f), or is repeated during or after steps (d), (e) and (f); and wherein the slurry is stirred at steps (d), (e) and (f). In a specific embodiment, the container comprises a flask and stirring occurs by a stir bar added to the flask. Any number of catalysts may be used, such as Grubbs Catalysts, with Grubbs Catalyst M204 being one example. U.S. Pat No. 11 ,001 ,673 describes other catalystsAttorney Docket Nol: 10457-605US0 that may be implemented in the methods herein. In one example, removal of ethylene by vacuum involves multiple vacuum applications to the mixture as polymerization in step (b) occurs. FIG. 3 provides general reaction scheme as one example of the above described method.

[0018] In a further embodiment, the polymer is hydrogenated (saturated), and depending on polymer, Boc deprotected.

[0019] A non-limiting list of monomers that may be used in the ADMET polymerization method are provided in FIG. 4.

[0020] The resulting polymers produced by the methods described herein can be characterized, such as by HNMR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).EXAMPLESExample 1 : General Protocol

[0021] Before running ADMet:• validate monomer purity (extraction, column and distillation if needed)• all monomer and solvent both need N2 sparkling 2h and vacuum Ih (large scale need Freeze -pump-thaw solvent)• Flame dry Round bottle (Vacuum-N2 circle 3 times)When setup, initiate ADMet (neat):• add Pure monomer in Flame dry Round bottle under N2 protection (FIG. 4 provides a nonlimiting list of monomers)• add Grubbs Catalyst M204 (1 mol%) into Round bottle under N2 protection• Quick Vacuum-N2 circle 3 times, leave the system under vacuum, stir and heat at 70 °CDuring ADMet running (slurry):Attorney Docket Nol: 10457-605US0• with ethylene removed by vacuum, the reaction will become sticky and hard to stir evenly, then add dichlorobenzene (DCB) (IM)• Run reaction 5d, need add DCB 2-4 times

[0022] ADMET Slurry Polymerization: In a flame-dried round-bottom flask equipped with a magnetic stir bar, we add 1 equivalent of monomer under a nitrogen atmosphere. We then evacuate the reaction flask and replace the atmosphere with nitrogen three times to ensure an inert atmosphere. We then introduce 1 mol% 2ndgeneration Grubbs catalyst (M204) and introduce it into the flask. We then repeat the evacuation / nitrogen cycling to remove residual oxygen. This mixture was then heated to 70 °C and stirred under vacuum for 5 days, which accelerates the removal of ethylene from the reaction mixture. When the stir bar visibly ceases to move (approximately 3 days), we cool the polymerization room temperature and add dichlorobenzene to the reaction mixture, with a target concentration of IM with respect to monomer, producing a slurry of polyolefin in dichlorobenzene. This mixture was then stirred for one day at room temperature under vacuum, after which time an additional amount of dichlorobenzene was added to reestablish a IM concentration. Throughout the course of the polymerization, a red color is maintained, which suggests that the Ru-based catalyst is still active. Upon intentional exposure to oxygen, this color is lost and black nanoparticles are produced.

[0023] FIG. 5 provides a general reactor setup and reaction scheme relating to a large scale stirred reactor. FIG. 6 shows a reaction scheme and setup using a round bottle.Example 2: Post-polymerization modification

[0024] In one example, a polymer with a Boc protected heteroatom was modified post polymerization by saturation and deprotection of the Boc group (see FIG. 10). Protocol: in the same flask used for the polymerization and under a nitrogen atmosphere, add dichloromethane to achieve a concentration of IM. Gradually add 10 equivalents of trifluoroacetic acid (TFA) to the flask. Allow the mixture to stir continuously for 22 hours under the nitrogen atmosphere. After 22 hours, remove the nitrogen atmosphere.

[0025] Similar hydrogenation and Boc deprotection (depending on monomer used) can be applied to other polymers. Also, other hydrogenation strategies are presented in FIG. 10.Attorney Docket Nol: 10457-605US0Example 3: Characterization of 6C-NBoc AdMet Polymer

[0026] HNMR and GPC analysis was conducted on a 6C-NBoc Admet polymer (see FIG. 7A-C). FIG. 7B shows a graph of the GPC analysis. FIG. 7C shows the HNMR is a graph of the ’HNMR analysis.

[0027] TGA and DSC analysis was also conducted on the 6C-NBoc-AdMet polymer (see FIG. 8A-C). FIG. 8B shows a graph representing the TGA analysis. FIG. 8C shows a graph representing the DSC analysis. These data show that at higher molecular weights, the thermal properties of these materials are virtually unchanged.

[0028] Shear rheology analysis was also conducted on the 6C-NBoc-AdMet polymer (see FIG. 9). This data was conducted at variable temperatures with a reference temperature of 60 °C. This data shows that the high molecular weight materials are more resilient to deformation than what one would expect for lower temperature analogues. This data shows that larger amounts of entanglements and larger crystallites are found in higher molecular weight samples.Example 4: Characterization of 6C-NH-ADMet polymer

[0029] TGA and DSC analysis was also conducted on the 6C-NH-AdMet polymer (see FIG. 11 A- C). FIG. 1 IB shows a graph representing the TGA analysis. FIG. 11C shows a graph representing the DSC analysis. This data shows that high molecular weight samples are also amenable to complete hydrogenation. This leads to high thermal stabilities and high amounts of crystallinity. These data validate that these approaches are amenable to creating precisely functionalized polyolefin copolymers with modest molecular weights.

Claims

Attorney Docket Nol: 10457-605US0CLAIMSWhat is claimed is:

1. A method of conducting ADMET polymerization in a si urry, the method comprising(a) mixing an amount of monomer and an amount of catalyst in a container under N2 protection to form a mixture;(b) heating the mixture while stirring such that polymerization occurs and ethylene is produced as a byproduct;(c) removing the ethylene from the container via vacuum;(d) adding an amount of dichlorobenzene to the container as solidity of the mixture increases, wherein addition of the dichlorobenzene reduces solidity of the mixture to create a slurry;(e) subsequent to step (d), and as solidity of the slurry increases, adding an additional amount of dichlorobenzene to reduce solidity of the slurry; and(f) repeating step (e) 1-4 times to produce polymer; and wherein, optionally, step (c) occurs continuously during steps (d), (c) and (f), or is repeated during or after steps (d), (e) and (f); and wherein, optionally, the slurry is stirred at steps (d), (e) and (f).

2. The method of claim 1, wherein the container comprises a flask and stirring occurs by a stir bar added to the flask.

3. The method of claim 1 or 2, wherein the catalyst is a Grubbs Catalyst.

4. The method of claim 3, wherein the Grubbs Catalyst is Grubbs Catalyst M204.

5. The method of any of claims 1-4, wherein removing ethylene by vacuum comprises multiple vacuum applications to the mixture as polymerization in step (b) occurs.

6. The method of any of claims 2-5, wherein an increase or reduction of solidity is associated with a decrease or increase, respectively, of movement of the stir bar.Attorney Docket Nol: 10457-605US07. The method of any of claims 1-6, wherein the monomer is subjected to extraction, column chromatography and / or distillation prior to step (a).

8. The method of any of claims 1-6, wherein the monomer is subjected to N2 sparkling and vacuum prior to step (a).

9. The method of any of claims 1-8, wherein the container is subjected to flame-drying, nitrogen exposure and vacuum prior to step (a).

10. The method of any of claims 1-9, wherein the catalyst is a Grubbs catalyst.

11. The method of claim 10, wherein the Grubbs catalyst is M204.

12. The method of any of claims 1-11, further comprising modifying the polymer.

13. The method of claim 12, wherein modifying comprises hydrogenation.

14. The method of any of claims 1-13, further comprising characterizing the polymer by subjecting it to by HNMR. gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and / or shear rheology.

15. The method of any of claims 1-14, wherein the monomer is selected from16. A polymer made by the method of any of claims 1-15.

17. The polymer of claim 16, wherein the polymer comprises a molecular weight of at least 50k g / mol, or at least 100k g / mol.

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