Acetal structure-containing polyurethane capable of controllably degrading acid enzyme as well as preparation method and application of acetal structure-containing polyurethane

Abstract

The invention discloses acetal structure-containing polyurethane capable of being controllably degraded by acid enzyme as well as a preparation method and application of the acetal structure-containing polyurethane. The polyurethane comprises hard segment structures with an acid-controlled degradation function and soft segment structures with an enzyme-controlled degradation function, and the soft segment structures and the hard segment structures are alternately distributed; the soft segment structure comprises polycaprolactone glycol and polytetrahydrofuran ether glycol, and the hard segment structure is formed by reacting a chain extender containing an acetal structure with isocyanate. The acetal structure-containing polyurethane capable of being controllably degraded by the acid enzyme provided by the invention has excellent mechanical properties, thermal properties and good optical permeability, and has a controllable degradation characteristic; meanwhile, the preparation method disclosed by the invention has the characteristics of simple process, controllable material performance, raw material bio-based source, controllable degradation, high optical transparency and the like, and the material is suitable for multiple fields such as flexible electronic devices and degradable packaging materials and has extremely wide application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane, and in particular relates to an acid enzyme-controllably degradable polyurethane containing an acetal structure, and a preparation method and application thereof. Background Art

[0002] Polyurethane materials are widely used in many fields, such as electronic devices, medical devices and flexible electronic devices, due to their excellent physical properties and structural diversity. However, traditional polyurethane is difficult to degrade and recycle, which may have adverse effects on the environment during waste disposal. Therefore, how to achieve efficient recycling and controllable degradation of polyurethane materials has become one of the important research directions, especially with the increasing attention to environmental protection and sustainable development of resources.

[0003] In recent years, the main drawback of traditional polyurethane is that its chemical structure is stable and difficult to degrade naturally. After being discarded, it accumulates in the environment for a long time, causing ecological burden. In addition, the cross-linked structure of polyurethane materials makes recycling difficult, and existing recycling technologies are difficult to effectively achieve resource recycling, which increases environmental burden and resource waste. In order to overcome these defects, the development of controllable degradable polyurethane containing acetal structure has become a research hotspot due to its unique structural characteristics. By introducing acetal structure into the polyurethane molecular chain, precise control of the degradation performance of the material can be achieved. In an acidic environment, the acetal structure is susceptible to acid-catalyzed hydrolysis, resulting in the disintegration of the molecular chain of polyurethane. At the same time, the introduction of ester bonds that are easy to be hydrolyzed by enzymes allows further degradation under the action of enzymes, achieving synergistic degradation of acids and enzymes. This synergistic effect makes the degradation process of the material more efficient and controllable, which is conducive to the recovery and reuse of materials.

[0004] By adjusting the concentration of acid and enzyme, temperature and other environmental factors, the degradation rate of polyurethane can be flexibly controlled, thus having a high degree of adjustability in practical applications. Compared with traditional non-degradable or difficult-to-recycle polyurethanes, controllable degradable polyurethanes containing acetal structures have great potential in terms of environmental friendliness and sustainable utilization. For example, this material can be used in flexible electronic devices as a base material for flexible electrodes, with high flexibility and excellent mechanical properties, and can be recycled through acid treatment after the end of its service life.

[0005] In summary, the development of polyurethanes containing acetal structures that can be controlled to degrade through the synergistic action of acids and enzymes can not only overcome the defects of traditional polyurethanes that are difficult to degrade and recycle, effectively improve their environmental performance, but also promote their wide application in the fields of electronics and medical treatment. At present, there are no reports on polyurethane materials with acid-enzyme synergistic degradation and controllable degradation rate. This research direction has broad prospects. Summary of the invention

[0006] The main purpose of the present invention is to provide an acid enzyme controllably degradable polyurethane containing an acetal structure and a preparation method and application thereof, so as to overcome the shortcomings of the prior art.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: The embodiment of the present invention provides an acid enzyme controllably degradable polyurethane containing an acetal structure, wherein the polyurethane comprises a hard segment structure having an acid-controlled degradation function and a soft segment structure having an enzyme-controlled degradation function, wherein the soft segment structure and the hard segment structure are alternately distributed; the soft segment structure comprises polycaprolactone diol and polytetramethylene glycol, and the hard segment structure is formed by reacting a chain extender containing an acetal structure with isocyanate; the chain extender containing an acetal structure has a structure as shown in formula (I): ; Formula (I) Wherein, R, R1, and R2 are independently selected from alkyl, alkenyl, alkynyl, monocyclic alkyl, bicyclic alkyl or aromatic ring.

[0008] The embodiment of the present invention also provides a method for preparing the aforementioned polyurethane containing an acetal structure and controllably degradable by acid enzyme, which comprises: Under a protective atmosphere, a mixed reaction system containing at least polycaprolactone diol, polytetramethylene glycol, isocyanate, a chain extender containing an acetal structure, a catalyst and a solvent is reacted to prepare an acid enzyme-controllably degradable polyurethane containing an acetal structure.

[0009] The embodiments of the present invention also provide the use of the aforementioned polyurethane containing an acetal structure and controllably degradable by acid enzymes in the preparation of flexible electronic devices or degradable packaging materials.

[0010] The embodiment of the present invention also provides a method for recovering polyurethane, which comprises: The product prepared by using the aforementioned polyurethane controllably degradable by acid enzyme containing acetal structure is placed in an acidic solution containing degradable enzyme for degradation, thereby realizing the recovery of polyurethane.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) The polyurethane containing an acetal structure and controllably degradable by acid enzymes provided by the present invention has excellent mechanical properties. At the same time, the polyurethane can be controlled by enzymes and / or acids in a solution containing a degrading enzyme and / or an acid. At the same time, the present invention uses biodegradable polycaprolactone diol, which is environmentally friendly and can partially recycle and reuse raw materials. Polytetramethylene glycol is used to break the crystallinity, which plays an important role in performance. (2) The method for preparing a polyurethane containing an acetal structure that is controllably degradable by an acid enzyme provided by the present invention has the characteristics of readily available raw materials, simple process, and multifunctional integration. The polyurethane is synthesized by using bio-based degradable polycaprolactone diol and polytetramethylene glycol, and the acetal structure-containing chain extender is used in conjunction to realize controllable degradation and recycling functions. At the same time, the ester bond of the polyester soft segment serves as a degradation site, and the acetal structure formed by the chain extender and isocyanate serves as an acid-controlled degradation site to realize the degradation function. The prepared polyurethane containing an acetal structure that is controllably degradable by an acid enzyme has broad application prospects in the fields of flexible devices, degradable packaging materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 1 is a schematic structural diagram of a polyurethane containing an acetal structure that can be controlled by an acid enzyme in a typical embodiment of the present invention; Figure 2 Schematic diagram of the degradation site of polyurethane containing acetal structure that can be controlled by acid enzyme degradation in a typical embodiment of the present invention; Figure 3 is a hydrogen nuclear magnetic resonance spectrum of the acid enzyme controllably degradable polyurethane containing acetal structure prepared in Examples 1-5 of the present invention; Figure 4 This is a graph showing the test results of the transmittance of the polyurethane containing acetal structure and controllably degradable by acid enzyme in the visible wavelength range prepared in Examples 1-5 of the present invention; Figure 5 1 is a graph showing the mechanical properties of the polyurethane containing acetal structure and controllably degradable by acid enzyme prepared in Examples 1-5 of the present invention; Figure 6 This is a graph showing the change in mass loss of the polyurethane containing an acetal structure that can be controlled by an acid enzyme in Examples 1-5 of the present invention before and after degradation in a phosphate buffer solution containing a degradation enzyme for 28 days; Figure 7 This is a graph showing the change in mass loss of the polyurethane containing an acetal structure that can be controlled by acid enzyme degradation in Examples 1-5 of the present invention before and after degradation in a 1 mol / L hydrochloric acid aqueous solution for 28 days; Figure 8 This is a graph showing the mass loss changes of the polyurethane containing an acetal structure in Examples 1-5 of the present invention after being degraded in a phosphate buffer solution containing a degrading enzyme for 14 days and then in a 1 mol / L hydrochloric acid aqueous solution for 14 days, for a total of 28 days; Fig. 9 This is a schematic diagram of the surface morphology of the degradation process of the polyurethane containing acetal structure and controllably degradable by acid enzyme prepared in Example 1 of the present invention; Fig.10 This is a comparison diagram of the acid enzyme-controllably degradable polyurethane containing an acetal structure prepared in Example 1 of the present invention before and after degradation in a phosphate buffer solution containing a degrading enzyme and a 1 mol / L hydrochloric acid aqueous solution for 28 days; Fig.11 1 is a TGA curve diagram of the polyurethane containing acetal structure and controllably degradable by acid enzyme prepared in Examples 1-5 of the present invention. DETAILED DESCRIPTION

[0014] In view of the defects of the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] Specifically, as one aspect of the technical solution of the present invention, an acid enzyme-controllable degradable polyurethane containing an acetal structure comprises a hard segment structure having an acid-controlled degradation function and a soft segment structure having an enzyme-controlled degradation function, wherein the soft segment structure and the hard segment structure are alternately distributed; the soft segment structure comprises polycaprolactone diol and polytetramethylene glycol, and the hard segment structure is formed by reacting a chain extender containing an acetal structure with isocyanate; the chain extender containing an acetal structure has a structure as shown in formula (I): ; Formula (I) Wherein, R, R1, and R2 are independently selected from alkyl, alkenyl, alkynyl, monocyclic alkyl, bicyclic alkyl or aromatic ring.

[0016] In the present invention, polycaprolactone diol: provides an ester bond as the main site for enzyme-controlled degradation, and its crystallinity improves the mechanical strength of the material and can adjust the degradation rate. Polytetramethylene ether diol: destroys part of the crystalline structure of PCL to form an amorphous region, making the material easier to degrade and improving the flexibility of the material. Chain extender containing acetal structure: the acetal structure is easily hydrolyzed in an acidic environment, thereby providing a breaking point for acid-controlled degradation and achieving precise degradation control. The synergistic effect of the three enables the material to achieve a controllable degradation process under the dual action of acid and enzyme. The combination of PCL and PTMG provides a balance between mechanical properties and degradation flexibility, while the chain extender containing acetal structure ensures the preferential degradation characteristics of the material in an acidic environment. Therefore, only by adopting the combination of these three can the efficient and controllable degradation of polyurethane under the synergistic conditions of acid and enzyme be achieved, while other diols cannot achieve the same effect.

[0017] In some preferred embodiments, the acetal structure-containing chain extender includes an aliphatic diol or an aromatic diol having a spiro acetal structure, and is not limited thereto.

[0018] In some preferred embodiments, the molecular weight of the chain extender containing an acetal structure is 100-1000 g / mol.

[0019] In some preferred embodiments, the molecular weight of the polycaprolactone diol is 600-6000.

[0020] In some preferred embodiments, the molecular weight of the polytetramethylene ether glycol is 600-6000.

[0021] In some preferred embodiments, the polyurethane has a structure as shown in formula (II): ; Formula (II) Wherein, R, R1, and R2 are independently selected from alkyl, alkenyl, alkynyl, monocyclic alkyl, bicyclic alkyl or aryl, R3 and R4 are independently derived from isocyanate, p and q are independently selected from 1 to 10; n and m are independently selected from 1 to 100.

[0022] The schematic diagram of the structure of the polyurethane containing acetal structure that can be controlled by acid enzyme degradation in the present invention is as follows Figure 1 As shown, it includes a soft segment structure with enzyme-controlled degradation and recovery (polycaprolactone diol and polytetramethylene glycol mixed soft segment, mainly a soft segment containing an ester bond, and the addition of polytetramethylene glycol breaks the crystallinity to facilitate degradation) and an acid-controlled degradation and recovery hard segment containing an acetal structure to jointly play a controllable degradation and recovery. The soft segment structure and the hard segment structure are alternately distributed. The schematic diagram of the degradation site is shown in Figure 2 shown.

[0023] The acid enzyme controllably degradable polyurethane containing acetal structure in the present invention can break the acetal structure by acid stimulation and break the ester bond under enzyme stimulation, so as to achieve acid enzyme synergistic degradation, and the degradation recovery rate can be controlled by regulating factors such as the concentration of acid and enzyme.

[0024] In some preferred embodiments, the polyurethane is degraded in a phosphate buffer solution containing a degrading enzyme for 28 days, and the mass loss can reach 10%.

[0025] In some preferred embodiments, the polyurethane is degraded in a 1 mol / L hydrochloric acid aqueous solution for 28 days, and the mass loss can reach 25%.

[0026] In some preferred embodiments, the polyurethane is degraded in a phosphate buffer solution containing a degradable enzyme at a pH of 0 for 28 days with a mass loss of more than 32%.

[0027] In some preferred embodiments, the acid enzyme-controllably degradable polyurethane containing acetal structure has a tensile strength of 48.93 MPa, an elongation at break of 904.41%, and a fracture toughness of 117.1 MJ / m3 at a tensile rate of 50 mm / min, and has good puncture resistance.

[0028] Another aspect of the embodiments of the present invention further provides a method for preparing the aforementioned polyurethane containing an acetal structure and controllably degradable by acid enzyme, which comprises: Under a protective atmosphere, a mixed reaction system containing at least polycaprolactone diol, polytetramethylene glycol, isocyanate, a chain extender containing an acetal structure, a catalyst and a solvent is reacted to prepare an acid enzyme-controllably degradable polyurethane containing an acetal structure.

[0029] In some preferred embodiments, the preparation method specifically comprises: reacting a mixed reaction system comprising polycaprolactone diol, polytetramethylene glycol, chain extender, catalyst and solvent at 25-100° C. for 1-48 hours under a protective atmosphere to obtain an acid enzyme-controllably degradable polyurethane containing an acetal structure.

[0030] In some preferred embodiments, the preparation method specifically includes: under a protective atmosphere, mixing polycaprolactone diol, polytetramethylene glycol, a chain extender, a catalyst and a solvent and heating them at 25-100°C until they are completely dissolved, then adding isocyanate to form the mixed reaction system, while controlling the concentration of the reactants in the mixed reaction system to be 10-50wt%, then reacting at 25-100°C for 1-48h, and then post-treating to obtain an acid enzyme-controllably degradable polyurethane containing an acetal structure.

[0031] In some preferred embodiments, the isocyanate includes a diisocyanate, and the diisocyanate includes any one or more combinations of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,5-naphthyl diisocyanate, p-phenylene diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, diphenylmethane diisocyanate, trimethylene diisocyanate, dibenzofuran diisocyanate, and 1,4-cyclohexane diisocyanate, and is not limited thereto.

[0032] In some preferred embodiments, the chain extender containing an acetal structure includes any one or more combinations of 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, pentaerythritol acetal diol, glycerol acetal diol, ethylene glycol acetal diol, 1,3-propylene glycol acetal diol, 1,4-butanediol acetal diol, dimethylolpropionic acid acetal diol, trimethylolethane acetal diol, tetramethylolcyclohexane acetal diol, isosorbide acetal diol, and diglycerol acetal diol, and is not limited thereto.

[0033] Furthermore, the chain extender containing an acetal structure is 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane.

[0034] In some preferred embodiments, the catalyst includes any one or more combinations of bis(dimethylaminoethyl)ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, dibutyltin dilaurate, organic bismuth, triazine trimerization, and 1,4-diazabicyclo[2.2.2]octane catalysts, and is not limited thereto.

[0035] In some preferred embodiments, the solvent includes any one or more combinations of tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, 2-butanone, acetonitrile, and ethyl acetate, but is not limited thereto.

[0036] In some preferred embodiments, the protective atmosphere includes an inert gas atmosphere and / or a nitrogen atmosphere, but is not limited thereto.

[0037] Furthermore, the protective atmosphere is selected as argon atmosphere.

[0038] In some preferred embodiments, the molar ratio of the hydroxyl groups in the polycaprolactone diol and the polytetramethylene ether diol to the isocyanate groups in the isocyanate in the mixed reaction system is 0.5:1 to 2:1.

[0039] In some preferred embodiments, the molar ratio of the polycaprolactone diol to the polytetramethylene glycol is 0.1:1 to 10:1.

[0040] In some preferred embodiments, the mass ratio of the chain extender to the sum of polycaprolactone diol and polytetramethylene glycol is 1:99 to 99:1.

[0041] In some preferred embodiments, the content of the catalyst in the mixed reaction system is 0.1-1 wt %.

[0042] Furthermore, the post-treatment includes: after the reaction is completed, washing the obtained solid with a washing liquid, and then vacuum drying at 40-120° C. for 6-48 hours to obtain the acid enzyme-controllably degradable polyurethane containing the acetal structure.

[0043] Furthermore, the washing liquid includes deionized water and / or ethanol, and is not limited to this.

[0044] Another aspect of the embodiments of the present invention further provides the use of the aforementioned acid enzyme-controllably degradable polyurethane containing an acetal structure in the preparation of flexible electronic devices or degradable packaging materials.

[0045] The acid enzyme-controllably degradable polyurethane containing an acetal structure of the present invention has excellent mechanical properties, thermal properties and good optical transmittance, and has controllable degradation characteristics; at the same time, the preparation method of the present invention has the characteristics of simple process, controllable material properties, bio-based source of raw materials, controllable degradation, high optical transparency, etc. At the same time, the preparation method of the present invention has the characteristics of easy availability of raw materials and simple process, and the material is suitable for multiple fields such as flexible electronic devices and degradable packaging materials, and has extremely broad application prospects.

[0046] Another aspect of the embodiments of the present invention further provides a method for recovering polyurethane, comprising: The product prepared by using the aforementioned polyurethane controllably degradable by acid enzyme containing acetal structure is placed in an acidic solution containing degradable enzyme for degradation, thereby realizing the recovery of polyurethane.

[0047] The controlled degradation of the polyurethane with acid enzyme controllable degradation containing acetal structure provided by the present invention is achieved by polycaprolactone diol, polytetrahydrofuran ether diol and 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, wherein polycaprolactone diol is biodegradable, and polycaprolactone has certain crystallinity, while polytetrahydrofuran ether diol is amorphous. When the content of polycaprolactone diol is large, the crystallinity is relatively large, and the ester bond is relatively difficult to break, which affects the degradation performance. By adding a small amount of polytetrahydrofuran ether diol, the crystallization is broken, so that it is easy to degrade in an amorphous state, and the bishydroxydimethyl spirocycloundecane containing acetal structure can be broken under the condition of acid stimulation, and the content of bishydroxydimethyl spirocycloundecane is adjusted, thereby achieving the purpose of controlled degradation.

[0048] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and drawings. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0049] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0050] In the embodiment of the present invention, the nuclear magnetic resonance hydrogen spectrum 1 H-NMR was measured using a Bruker 400 AVANCEⅢ spectrometer, 400 MHz, deuterated chloroform (CDCl3). According to the test standard of ASTM D 882, the mechanical properties of the polyurethane specimens were measured on a 1KN universal testing machine (UTM, Zwick Instruments, Model: Z1.0), with a tensile rate of 50 mm / min. The UV-visible (UV-vis) spectrum was received by a UV-visible spectrophotometer (PerkinElmer Lambda 950, Perkin Elmer, USA) in the range of 200 to 800 nm. The degradation micromorphology was recorded by a scanning electron microscope (EVO18, Carl Zeiss, Germany) at an accelerating voltage of 20 kV to record the morphological changes of the degradation process. Thermal analysis was tested by a thermogravimeter (TGA09F1, Germany).

[0051] Example 1 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetrahydrofuran ether diol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 1 / 99 (mass ratio), the molecular weight of polycaprolactone diol and polytetrahydrofuran ether diol are both 2000 g / mol, the molar ratio of polycaprolactone diol to polytetrahydrofuran ether diol is 10:1, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10 wt%, the reaction temperature is 55 ℃, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 ℃ for 12 h to constant weight to obtain polyurethane PU-1 containing acetal structure that can be controlled by acid enzyme degradation. (NMR hydrogen spectrum see Figure 3 , the transmittance in the visible light wavelength range is Figure 4 , mechanical properties see Figure 5 , degradable properties see Figure 6 , Figure 7 , Figure 8 , Fig. 9 , Fig.10 , thermal analysis see Fig.11 ).

[0052] Example 2 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. The reaction conditions are [polycaprolactone diol] and [polytetrahydrofuran ether diol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 50 / 50 (mass ratio), the molecular weight of polycaprolactone diol and polytetrahydrofuran ether diol are both 2000 g / mol, the molar ratio of polycaprolactone diol to polytetrahydrofuran ether diol is 1:1, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10 wt%, the reaction temperature is 25 °C, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 °C for 12 h to constant weight to obtain an acid enzyme-controllably degradable polyurethane PU-2 containing an acetal structure. (NMR hydrogen spectrum see Figure 3 , the transmittance in the visible light wavelength range is Figure 4 , mechanical properties see Figure 5 , degradable properties see Figure 6 , Figure 7 , Figure 8 , thermal analysis see Fig.11 ).

[0053] Example 3 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetrahydrofuran ether diol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 99 / 1 (mass ratio), the molecular weight of polycaprolactone diol and polytetrahydrofuran ether diol is 600 g / mol, the molar ratio of polycaprolactone diol to polytetrahydrofuran ether diol is 1:1, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10 wt%, the reaction temperature is 25 ℃, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 ℃ for 12 h to constant weight to obtain polyurethane PU-3 containing acetal structure that can be controlled by acid enzyme degradation. (NMR hydrogen spectrum see Figure 3 , the transmittance in the visible light wavelength range is Figure 4 , mechanical properties see Figure 5 , degradable properties see Figure 6 , Figure 7 , Figure 8 , thermal analysis see Fig.11 ).

[0054] Example 4 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetrahydrofuran ether diol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 1 / 99 (mass ratio), the molecular weight of polycaprolactone diol and polytetrahydrofuran ether diol are both 6000 g / mol, the molar ratio of polycaprolactone diol to polytetrahydrofuran ether diol is 1:1, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10 wt%, the reaction temperature is 25 °C, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 °C for 12 h to constant weight to obtain polyurethane PU-4 containing acetal structure that can be controlled by acid enzyme degradation. (NMR hydrogen spectrum see Figure 3 , the transmittance in the visible light wavelength range is Figure 4 , mechanical properties see Figure 5 , degradable properties see Figure 6 , Figure 7 , Figure 8 , thermal analysis see Fig.11 ).

[0055] Example 5 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetrahydrofuran ether diol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 50 / 50 (mass ratio), the molecular weight of polycaprolactone diol and polytetrahydrofuran ether diol are both 2000 g / mol, the molar ratio of polycaprolactone diol to polytetrahydrofuran ether diol is 1:1, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10 wt%, the reaction temperature is 25 ℃, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 ℃ for 12 h to constant weight to obtain polyurethane PU-5 containing acetal structure that can be controlled by acid enzyme degradation. (NMR hydrogen spectrum see Figure 3 , the transmittance in the visible light wavelength range is Figure 4 , mechanical properties see Figure 5 , degradable properties see Figure 6 , Figure 7 , Figure 8 , thermal analysis see Fig.11 ).

[0056] Example 6 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 1 / 99 (mass ratio), the molecular weight of polycaprolactone diol and polytetramethylene glycol is 500 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 1:1, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl group to isocyanate group is 0.5:1, the concentration of all reactants is 10 wt%, the reaction temperature is 25 ℃, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 ℃ for 12 h to constant weight to obtain an acid enzyme-controllably degradable polyurethane PU-6 containing an acetal structure.

[0057] Example 7 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dimethylaminoethyl ether and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 1 / 99 (mass ratio), the molecular weights of polycaprolactone diol and polytetramethylene glycol are both 1000 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 1:2, dimethylaminoethyl ether accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10 wt%, the reaction temperature is 25 °C, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 °C for 12 h to constant weight to obtain an acid enzyme-controllably degradable polyurethane PU-7 containing an acetal structure.

[0058] Example 8 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dimethylaminoethyl ether and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 50 / 50 (mass ratio), the molecular weights of polycaprolactone diol and polytetramethylene glycol are both 1000 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 1:2, dibutyltin dilaurate accounts for 0.5 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 1:1, the concentration of all reactants is 10 wt%, the reaction temperature is 30 °C, the reaction time is 2 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 °C for 12 h to constant weight to obtain an acid enzyme-controllably degradable polyurethane PU-8 containing an acetal structure.

[0059] Example 9 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dimethylaminoethyl ether and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane]=75 / 25 (mass ratio), the molecular weight of polycaprolactone diol and polytetramethylene glycol is 1500 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 1:1, dimethylaminoethyl ether accounts for 1 wt% of the total mass of the reactants, the molar ratio of hydroxyl group to isocyanate group is 1:5, the concentration of all reactants is 20 wt%, the reaction temperature is 35 ℃, the reaction time is 2 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 ℃ for 12 h to constant weight to obtain the acid enzyme-controllably degradable polyurethane PU-9 containing acetal structure.

[0060] Example 10 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, pentaerythritol acetal diol, organic bismuth and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [pentaerythritol acetal diol] = 25 / 75 (mass ratio), the molecular weight of polycaprolactone diol and polytetramethylene glycol is 2000 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 1:5, organic bismuth accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl group to isocyanate group is 1:1, the concentration of all reactants is 10 wt%, the reaction temperature is 40 ℃, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 ℃ for 12 h to constant weight to obtain an acid enzyme-controllably degradable polyurethane PU-10 containing an acetal structure.

[0061] Embodiment 11 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 10 / 90 (mass ratio), the molecular weights of polycaprolactone diol and polytetramethylene glycol are both 2500 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 1:5, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 1:2, the concentration of all reactants is 30 wt%, the reaction temperature is 45 ℃, the reaction time is 3 h, and finally, the polymer precipitate is washed several times with deionized water and vacuum dried at 60 ℃ for 12 h to constant weight to obtain an acid enzyme-controllably degradable polyurethane PU-11 containing an acetal structure.

[0062] Example 12 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol ether diol, 1,3-propylene glycol acetal diol, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, which was sealed and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetrahydrofuran ether diol] / [1,3-propylene glycol acetal diol] = 1 / 99 (mass ratio), the molecular weight of polycaprolactone diol and polytetrahydrofuran ether diol is 600 g / mol, the molar ratio of polycaprolactone diol to polytetrahydrofuran ether diol is 1:5, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl group to isocyanate group is 0.5:1, the concentration of all reactants is 10wt%, the reaction temperature is 100 ℃, and the reaction time is 1 h. Finally, the polymer precipitate is washed with deionized water several times, and vacuum dried at 60 ℃ for 12 h to constant weight to obtain polyurethane PU-12 containing acetal structure that can be controlled by acid enzyme degradation.

[0063] Embodiment 13 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetrahydrofuran ether diol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 1 / 99 (mass ratio), the molecular weight of polycaprolactone diol and polytetrahydrofuran ether diol are both 600 g / mol, the molar ratio of polycaprolactone diol to polytetrahydrofuran ether diol is 1:5, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 20wt%, the reaction temperature is 60 ℃, and the reaction time is 1h. Finally, the polymer precipitate is washed with deionized water several times, and vacuum dried at 60 ℃ for 12 h to constant weight to obtain the acid enzyme-controllably degradable polyurethane PU-13 containing acetal structure.

[0064] Embodiment 14 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetrahydrofuran ether diol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 1 / 99 (mass ratio), the molecular weight of polycaprolactone diol and polytetrahydrofuran ether diol are both 2000 g / mol, the molar ratio of polycaprolactone diol to polytetrahydrofuran ether diol is 1:5, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10wt%, the reaction temperature is 25 ℃, and the reaction time is 48h. Finally, the polymer precipitate is washed with deionized water several times, and vacuum dried at 40 ℃ for 48h to constant weight to obtain polyurethane PU-14 containing acetal structure that can be controlled by acid enzyme degradation.

[0065] Embodiment 15 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 1 / 99 (mass ratio), the molecular weights of polycaprolactone diol and polytetramethylene glycol are both 2000 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 1:5, dibutyltin dilaurate accounts for 0.5 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 1:1, the concentration of all reactants is 20 wt%, the reaction temperature is 50°C, the reaction time is 24h, and finally, the polymer precipitate is washed several times with deionized water and vacuum dried at 50°C for 24h to constant weight to obtain an acid enzyme-controllably degradable polyurethane PU-15 containing an acetal structure.

[0066] Example 16 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 1 / 99 (mass ratio), the molecular weights of polycaprolactone diol and polytetramethylene glycol are both 2000 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 1:5, dibutyltin dilaurate accounts for 1.0 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 2:1, the concentration of all reactants is 50 wt%, the reaction temperature is 100°C, the reaction time is 1h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 100°C for 1h to constant weight to obtain an acid enzyme-controllably degradable polyurethane PU-16 containing an acetal structure.

[0067] Embodiment 17 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane] = 1 / 99 (mass ratio), the molecular weights of polycaprolactone diol and polytetramethylene glycol are both 2000 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 8:1, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10wt%, the reaction temperature is 25 ℃, the reaction time is 1h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 ℃ for 48 h to constant weight to obtain an acid enzyme-controllably degradable polyurethane PU-17 containing an acetal structure.

[0068] Comparative Example 1 In a glove box filled with 99.999% Ar, polycaprolactone diol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. A one-step reaction was carried out, wherein [polycaprolactone diol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane]=1 / 99 (mass ratio), the molecular weight of polycaprolactone diol was 600 g / mol, dibutyltin dilaurate accounted for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl group to isocyanate group was 0.5:1, the concentration of all reactants was 10 wt%, the reaction temperature was 25 °C, the reaction time was 1 h, and finally the polymer precipitate was washed several times with deionized water and vacuum dried at 60 °C for 12 h to constant weight to obtain comparative polyurethane 1.

[0069] Comparative Example 2 In a glove box filled with 99.999% Ar, polytetramethylene glycol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polytetramethylene oxide ether diol] / [3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane]=1 / 99 (mass ratio), the molecular weight of polytetramethylene oxide ether diol is 2000 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene oxide ether diol is 10:1, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10 wt%, the reaction temperature is 55 °C, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 °C for 12 h to constant weight to obtain comparative polyurethane 2.

[0070] Comparative Example 3 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetrahydrofuran ether diol, dibutyltin dilaurate and tetrahydrofuran were added to a three-necked reactor equipped with a mechanical stirrer, sealed, and then removed to an oil bath for a one-step reaction. After the above reaction was completely dissolved, isophorone diisocyanate was added dropwise. Among them, the molecular weights of polycaprolactone diol and polytetrahydrofuran ether diol were both 2000 g / mol, the molar ratio of polycaprolactone diol to polytetrahydrofuran ether diol was 10:1, dibutyltin dilaurate accounted for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups was 0.5:1, the concentration of all reactants was 10 wt%, the reaction temperature was 55 ℃, the reaction time was 1 h, and finally the polymer precipitate was washed several times with deionized water and vacuum dried at 60 ℃ for 12 h to constant weight to obtain comparative polyurethane 3.

[0071] Comparative Example 4 In a glove box filled with 99.999% Ar, polycaprolactone diol, polytetramethylene glycol, 1,4-butanediol, dibutyltin dilaurate and tetrahydrofuran were added into a three-necked reactor equipped with a mechanical stirrer, which was sealed and then removed to an oil bath for a one-step reaction. After the above reaction mixture was completely dissolved, isophorone diisocyanate was added dropwise. Among them, [polycaprolactone diol] and [polytetramethylene glycol] / [1,4-butanediol] = 1 / 99 (mass ratio), the molecular weight of polycaprolactone diol and polytetramethylene glycol is 2000 g / mol, the molar ratio of polycaprolactone diol to polytetramethylene glycol is 10:1, dibutyltin dilaurate accounts for 0.1 wt% of the total mass of the reactants, the molar ratio of hydroxyl groups to isocyanate groups is 0.5:1, the concentration of all reactants is 10 wt%, the reaction temperature is 55 °C, the reaction time is 1 h, and finally the polymer precipitate is washed several times with deionized water and vacuum dried at 60 °C for 12 h to constant weight to obtain comparative polyurethane 4.

[0072] Performance characterization: 1. Nuclear Magnetic Resonance ( 1 H-NMR) The analysis was performed on an AVANCE III (400 MHz) at room temperature using tetramethylsilane as an internal standard. 1 H-NMR spectra, sample concentration was 1-5wt%.

[0073] 2. Optical transmittance The spectra were collected by a UV-visible spectrophotometer (PerkinElmer Lambda 950, Perkin Elmer, USA) in the range of 200 to 800 nm.

[0074] from Figure 4It can be seen that the acid enzyme-controllably degradable polyurethane containing acetal structure prepared in Examples 1-5 has a transmittance greater than 92% in the visible light wavelength range above 750 nm, which can meet the needs of different conditions.

[0075] 3. Mechanical properties The mechanical properties of the samples were measured using a universal testing machine (UTM, Zwick Instruments, model: Z1.0), and the tensile rate was maintained at 50 mm / min.

[0076] from Figure 5 It can be seen that the mechanical properties of the polyurethane containing acetal structure and controllably degradable by acid enzyme prepared in Examples 1-5 vary with the different components, and can meet the requirements of different conditions.

[0077] 4. Degradable performance from Figure 6 It can be seen that the mass loss reaches 10% during 28 days of degradation in a phosphate buffer solution containing a degrading enzyme, indicating that the polyurethane containing an acetal structure and controllably degradable by acid enzymes obtained in Examples 1-5 of the present invention has good controllable degradation performance.

[0078] from Figure 7 It can be seen that the mass loss reaches 25% after 28 days of degradation in 1 mol / L hydrochloric acid aqueous solution, indicating that the polyurethane containing acetal structure and controllably degradable by acid enzymes obtained in Examples 1-5 of the present invention has good controllable degradation performance.

[0079] from Figure 8 It can be seen that after 14 days of degradation in a phosphate buffer solution containing a degrading enzyme and then 14 days of degradation in a 1 mol / L hydrochloric acid aqueous solution, the mass loss reaches 32%, indicating that the acid enzyme-controllably degradable polyurethane containing an acetal structure obtained in Examples 1-5 of the present invention has good controllable degradation performance.

[0080] The degradation microstructure was recorded by scanning electron microscopy (EVO18, Carl Zeiss, Germany) at an accelerating voltage of 20 kV. Fig. 9 It can be seen that the polyurethane prepared in Example 1 was degraded in a phosphate buffer solution containing a degrading enzyme for 14 days, and then degraded in a 1 mol / L hydrochloric acid aqueous solution for 14 days. The surface microstructure after degradation was obviously broken compared with that before degradation.

[0081] from Fig.10 It can be seen that the state of the polyurethane prepared in Example 1 before and after degradation has changed greatly, and the sample after degradation is broken into many pieces, which indirectly verifies that the polyurethane containing acetal structure can be controllably degraded by acid enzyme into small molecules.

[0082] When the polyurethanes in Comparative Examples 1-4 were degraded in 1 mol / L hydrochloric acid aqueous solution for 28 days, the maximum mass loss was only 12%, which indicates that the polyurethanes synthesized without introducing acetal structure and / or without using mixed soft segments have poor degradation performance.

[0083] When the polyurethanes in Comparative Examples 1-4 were degraded in a phosphate buffer solution containing a degrading enzyme for 28 days, the maximum mass loss was only 5%, further indicating that their degradation performance was far inferior to that of the embodiments of the present invention.

[0084] When the polyurethane samples in Comparative Examples 1-4 were degraded in a phosphate buffer solution containing a degrading enzyme for 14 days and then further degraded in a 1 mol / L hydrochloric acid aqueous solution for 14 days, the maximum mass loss was only 15%. This indicates that the polyurethane without the introduction of acetal structure and / or the use of mixed soft segments does not have the characteristics of acid-enzyme coordinated controllable degradation.

[0085] 5. Thermal stability from Fig.11 It can be seen that the T values ​​of the polyurethanes containing acetal structures that can be controlled by enzyme degradation obtained in Examples 1-5 are d5% Above 270°C, it is shown that the prepared polyurethane containing acetal structure and controllably degradable by acid enzyme has good thermal stability.

[0086] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0087] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0088] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the protection scope of the present invention.

Claims

1. A polyurethane containing an acetal structure that can be controlled by enzyme degradation, characterized in that: The polyurethane comprises a hard segment structure with an acid-controlled degradation function and a soft segment structure with an enzyme-controlled degradation function, wherein the soft segment structure and the hard segment structure are alternately distributed; the soft segment structure comprises polycaprolactone diol and polytetramethylene glycol; the hard segment structure is formed by reacting a chain extender containing an acetal structure with isocyanate; the chain extender containing an acetal structure has a structure as shown in formula (I): ; Formula (I) Wherein, R, R1, and R2 are independently selected from alkyl, alkenyl, alkynyl, monocyclic alkyl, bicyclic alkyl or aromatic ring.

2. The polyurethane according to claim 1, characterized in that: The chain extender containing an acetal structure includes an aliphatic diol or an aromatic diol having a spiro acetal structure; and / or, the molecular weight of the chain extender containing the acetal structure is 100-1000 g / mol; and / or, the molecular weight of the polycaprolactone diol is 600-6000 g / mol; And / or, the molecular weight of the polytetramethylene ether glycol is 600-6000 g / mol.

3. The polyurethane according to claim 1, characterized in that The polyurethane has a structure as shown in formula (II): ; Formula (II) Wherein, R, R1, and R2 are independently selected from alkyl, alkenyl, alkynyl, monocyclic alkyl, bicyclic alkyl or aryl, R3 and R4 are independently derived from isocyanate, p and q are independently selected from 1 to 10; n and m are independently selected from 1 to 100.

4. The polyurethane according to claim 1, characterized in that: The polyurethane is degraded in a phosphate buffer solution containing a degradable enzyme and at a pH value of 0 for 28 days, with a mass loss of more than 32%.

5. The method for preparing the polyurethane containing acetal structure and controllably degradable by acid enzyme according to any one of claims 1 to 4, characterized in that: include; Under a protective atmosphere, a mixed reaction system containing at least polycaprolactone diol, polytetramethylene glycol, isocyanate, a chain extender containing an acetal structure, a catalyst and a solvent is reacted to prepare an acid enzyme-controllably degradable polyurethane containing an acetal structure.

6. The preparation method according to claim 5, characterized in that: Specifically include: Under a protective atmosphere, polycaprolactone diol, polytetramethylene glycol, a chain extender, a catalyst and a solvent are mixed and heated at 25-100° C. until they are completely dissolved, and then isocyanate is added to form the mixed reaction system. At the same time, the concentration of the reactants in the mixed reaction system is controlled to be 10-50wt%, and then the mixture is reacted at 25-100° C. for 1-48 hours, and then post-treated to obtain an acid enzyme-controllably degradable polyurethane containing an acetal structure.

7. The preparation method according to claim 5, characterized in that: The isocyanate includes a diisocyanate, and the diisocyanate includes any one or more combinations of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,5-naphthyl diisocyanate, p-phenylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, diphenylmethane diisocyanate, trimethylene diisocyanate, dibenzofuran diisocyanate, and 1,4-cyclohexane diisocyanate; And / or, the chain extender containing an acetal structure includes any one or more combinations of 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane, pentaerythritol acetal diol, glycerol acetal diol, ethylene glycol acetal diol, 1,3-propylene glycol acetal diol, 1,4-butanediol acetal diol, dimethylol propionic acid acetal diol, trimethylolethane acetal diol, tetramethylolcyclohexane acetal diol, isosorbide acetal diol, and diglycerol acetal diol; And / or, the catalyst comprises any one or more combinations of bis(dimethylaminoethyl)ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, dibutyltin dilaurate, organic bismuth, triazine trimerization, and 1,4-diazabicyclo[2.2.2]octane catalysts; And / or, the solvent includes any one or more combinations of tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, 2-butanone, acetonitrile, and ethyl acetate; and / or, the molar ratio of the hydroxyl groups in the polycaprolactone diol and the polytetramethylene ether diol to the isocyanate groups in the isocyanate in the mixed reaction system is 0.5:1 to 2:1; And / or, the molar ratio of the polycaprolactone diol to the polytetrahydrofuran ether diol is 0.1:1 to 10:1; And / or, the mass ratio of the chain extender to the sum of polycaprolactone diol and polytetramethylene glycol is 1:99 to 99:1; And / or, the content of the catalyst in the mixed reaction system is 0.1-1wt%.

8. The preparation method according to claim 5, characterized in that: The post-treatment comprises: after the reaction is completed, washing the obtained solid with a washing liquid, and then vacuum drying at 40-120° C. for 6-48 hours to obtain the polyurethane containing the acetal structure that can be controlled by acid enzyme degradation.

9. Use of the polyurethane containing an acetal structure and controllably degradable by acid enzyme according to any one of claims 1 to 5 in the preparation of flexible electronic devices or degradable packaging materials.

10. A method for recovering polyurethane, characterized in that: include: The product prepared by using the polyurethane containing acetal structure controllably degraded by acid enzyme according to any one of claims 1 to 5 is placed in an acidic solution containing degradable enzyme for degradation, thereby realizing the recovery of polyurethane.

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