A method for continuously dynamically reorganizing to produce a hydrophilic lubricating zwitterionic polyurethane and the zwitterionic polyurethane and applications thereof

Abstract

The application provides a method for continuously and dynamically recombining to prepare a hydrophilic lubricating zwitterionic polyurethane and the zwitterionic polyurethane and application thereof, and relates to the technical field of medical polymer materials for implant intervention. The application first synthesizes a polyurethane elastomer containing a dynamic tert-butyl urea bond and an ATRP initiator; then, the elastomer is crushed into fine particles, and a polyelectrolyte brush is introduced onto the surface of the particles through SI-ATRP reaction; the particles with the introduced polyelectrolyte brush are treated through hot pressing to obtain a uniform and transparent zwitterionic polyurethane film; after continuous crushing, grafting of the polyelectrolyte brush and hot pressing for multiple times, a zwitterionic polyurethane with a high polyelectrolyte brush content is obtained. The zwitterionic polyurethane prepared by the application contains a high content of polyelectrolyte brushes in the bulk and on the surface, has controllable mechanical and hydrophilic lubricating properties, and is expected to be widely applied in the field of medical devices for implant intervention.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of implant interventional medical polymer materials, and particularly relates to a method for continuously and dynamically recombining to prepare hydrophilic and lubricating zwitterionic polyurethane, and the zwitterionic polyurethane and application thereof. BACKGROUND

[0002] Implant interventional medical devices have been more and more widely used. As one of the most commonly used biomedical materials, polyurethane has the characteristics of controllable chemical structure, excellent mechanical properties and good biocompatibility, and has been widely used in catheters, tracheas, artificial joint cushions, meniscus substitutes and the like in recent years. At present, there are already several medical-grade polyurethane products on the market. However, polyurethane devices often exhibit a high coefficient of friction (COF) due to their hydrophobic surfaces, which often leads to complications such as tissue trauma, biofouling, postoperative pain and foreign body reactions in clinical use. Therefore, it is necessary to modify the polyurethane to be hydrophilic in order to reduce the COF between the polyurethane and the biological tissue, thereby reducing the pain of the patient.

[0003] A very effective method is to introduce zwitterionic polyelectrolyte brushes onto polyurethane to create zwitterionic polyurethane. This is mainly because zwitterionic groups have strong hydration ability, excellent biocompatibility, and anti-fouling and anti-bacterial adhesion ability. At present, there are mainly two methods for grafting polyelectrolyte brushes on polyurethane: one is to modify the polyelectrolyte brushes on the surface of polyurethane by physical coating, chemical coupling or chemical grafting, etc. to improve the hydrophilicity and stable lubricating performance. However, the initiator of this method mainly exists on the surface of the substrate, and there are generally problems such as poor adhesion, easy to fall off or wear under shear force, etc., which further leads to the loss of lubrication of the material. The other is bulk modification, which mainly refers to introducing zwitterionic groups such as phosphorylcholine, carboxybetaine and sulfobetaine into the main chain or side chain of polyurethane. Although this method solves the problem of poor adhesion, the content of zwitterionic groups in the zwitterionic polyurethane prepared by this method is relatively low, and the mechanical properties and hydrophilic and lubricating properties of the material are relatively fixed, which cannot meet the application requirements of different medical devices. SUMMARY

[0004] Therefore, the present application aims to provide a method for continuously and dynamically recombining to prepare hydrophilic and lubricating zwitterionic polyurethane, and the zwitterionic polyurethane and application thereof. The zwitterionic polyurethane prepared by the present application has controllable mechanical properties and hydrophilic and lubricating properties, and can meet the application requirements of different medical devices.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides a method for continuously and dynamically recombining to prepare hydrophilic and lubricating zwitterionic polyurethane, comprising the following steps:

[0007] polyol, diol, diisocyanate and organic solvent to perform a hydroxyl isocyanate reaction, mixing the obtained product with 2-(tert-butylamino)ethyl methacrylate to perform an amine isocyanate reaction, to obtain a polyurethane type acryl ester prepolymer containing a dynamic tert-butyl urea bond; the number of hydroxyl groups in the polyol is more than 3;

[0008] mixing the polyurethane type acryl ester prepolymer containing a dynamic tert-butyl urea bond with a dilution monomer and a photoinitiator to obtain a photocuring resin; the dilution monomer is grafted with an ATRP initiator;

[0009] performing photocuring on the photocuring resin to obtain a polyurethane elastomer containing a tert-butyl urea bond and an ATRP initiator;

[0010] performing the polyurethane elastomer containing a tert-butyl urea bond and an ATRP initiator in sequence with crushing, polyelectrolyte brush grafting and heat pressing operations, the sequence of crushing, polyelectrolyte brush grafting and heat pressing operations being repeated to obtain the hydrophilic lubricating zwitterionic polyurethane; the number of repetitions is ≥ 0 times.

[0011] Preferably, the diisocyanate includes one or more of isophorone diisocyanate, toluene diisocyanate, diphenyl methane diisocyanate, dicyclohexyl methane diisocyanate, hexamethylene diisocyanate and lysine diisocyanate; the polyol includes one or more of glycerol, pentaerythritol, trimethylolpropane, triethanolamine, xylitol and sorbitol; the diol includes one or more of polyethylene glycol, polytetrahydrofuran diol, polycarbonate diol and polycaprolactone diol.

[0012] Preferably, the molar ratio of hydroxyl groups in the polyol to isocyanate in the diisocyanate is (0.5-2):11; the molar ratio of hydroxyl groups in the diol to isocyanate in the diisocyanate is (2-8):11; the molar ratio of amine groups in the 2-(tert-butylamino)ethyl methacrylate to isocyanate in the diisocyanate is (3-8.5):11.

[0013] Preferably, the temperature of the hydroxyl isocyanate reaction is 30-150℃, and the time is 1-8h; the temperature of the amine isocyanate reaction is 0-100℃, and the time is 0.5-5h.

[0014] Preferably, the dilution monomer is obtained by nucleophilic substitution reaction of an ATRP initiator and a monomer, the ATRP initiator is 2-bromoisobutyryl bromide, and the monomer includes one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, allyl alcohol and methyl allyl alcohol.

[0015] Preferably, the mass of the diluent monomer is 10-40% of the mass of the photocuring resin, and the mass of the photoinitiator is 0.5-3% of the mass of the photocuring resin.

[0016] Preferably, the polyelectrolyte brush is one or more of poly(3-sulfopropyl methacrylate potassium salt), poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride, poly(N-isopropylacrylamide), poly(2-acrylamido-2-methylpropanesulfonic acid), poly(2-methacryloyloxyethyl phosphorylcholine), and poly(sulfobetaine methacrylate).

[0017] Preferably, the pressure of the single hot-pressing treatment is 2-15 MPa, the temperature is 80-180℃, and the time is 10-60 min.

[0018] The application provides a hydrophilic and lubricous zwitterionic polyurethane prepared by the method.

[0019] The application provides an application of the hydrophilic and lubricous zwitterionic polyurethane in the preparation of implant interventional medical devices.

[0020] The application provides a method for continuously and dynamically recombining a hydrophilic and lubricous zwitterionic polyurethane, which comprises the following steps: first, synthesizing a polyurethane elastomer containing a dynamic tertiary butyl urea bond and an ATRP initiator; then, crushing the elastomer into fine particles, and introducing a polyelectroylete brush onto the surface of the particles through SI-ATRP reaction; subjecting the particles with the introduced polyelectroylete brush to hot-pressing treatment to obtain a uniform and transparent zwitterionic polyurethane film; and repeating the crushing, polyelectroylete brush grafting and hot-pressing treatment multiple times to obtain a zwitterionic polyurethane with a high polyelectroylete brush content. In the application, the mechanical and hydrophilic and lubricous properties of the obtained zwitterionic polyurethane can be controlled by adjusting the number of times of the hot-pressing recovery, so as to meet the application requirements of different medical devices. The polyurethane elastomer synthesized in the application has good recycling and reprocessing capability, which is mainly due to the tertiary butyl urea (sterically hindered urea) structure formed by diisocyanate and 2-(tertiary butyl amino) ethyl methacrylate. The structure can be quickly broken and recombined during heating and cooling, thereby giving the material good dynamic recombination performance. In addition, the introduced zwitterionic polyelectroylete brush has strong hydration capacity, which can significantly improve the hydrophilic and lubricous capacity of the obtained zwitterionic polyurethane.

[0021] The application provides a hydrophilic and lubricous zwitterionic polyurethane prepared by the method. The zwitterionic polyurethane provided by the application contains a high content of polyelectroylete brushes in the bulk and on the surface, and has controllable mechanical and hydrophilic and lubricous properties, and is expected to be widely applied in the field of implant interventional medical devices. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The tensile strength of the zwitterionic polyurethane obtained under different cycle periods in step (8) of Example 1 is shown. Figure 1 The small images in the image are magnified views of specific areas;

[0023] Figure 2 The water contact angle of the zwitterionic polyurethane obtained under different cycle periods in step (8) of Example 1;

[0024] Figure 3 The tribological properties of zwitterionic polyurethane obtained under different cycle periods in step (8) of Example 1;

[0025] Figure 4 The sulfur distribution on the surface and cross-section of the zwitterionic polyurethane obtained under different cycle periods in step (8) of Example 1. Detailed Implementation

[0026] This invention provides a method for continuously and dynamically preparing hydrophilic and lubricating zwitterionic polyurethane, comprising the following steps:

[0027] A polyol, a diol, a diisocyanate, and an organic solvent are mixed to carry out a hydroxyisocyanation reaction. The resulting product is then mixed with ethyl 2-(tert-butylamino)methacrylate to carry out an aminoisocyanation reaction, thereby obtaining a polyurethane-type propylene ester prepolymer containing dynamic tert-butylurea bonds. The polyol contains three or more hydroxyl groups.

[0028] The polyurethane-type acrylic ester prepolymer containing dynamic tert-butylurea bonds is mixed with a diluent monomer and a photoinitiator to obtain a photocurable resin; the diluent monomer is grafted with an ATRP initiator.

[0029] The photocurable resin is photocured to obtain a polyurethane elastomer containing tert-butylurea bonds and an ATRP initiator;

[0030] The polyurethane elastomer containing tert-butylurea bonds and ATRP initiator is subjected to a series of operations including pulverization, polyelectrolyte brush grafting, and hot pressing. These operations are repeated to obtain the hydrophilic lubricating zwitterionic polyurethane. The number of repetitions is ≥0.

[0031] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.

[0032] This invention involves mixing polyol, diol, diisocyanate, and organic solvent to carry out a hydroxyisocyanate reaction, and then mixing the resulting product with ethyl 2-(tert-butylamino)methacrylate to carry out an aminoisocyanate reaction, thereby obtaining a polyurethane-type propylene ester prepolymer containing dynamic tert-butylurea bonds.

[0033] In this invention, the diisocyanate preferably includes one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate. In this invention, the polyol has three or more hydroxyl groups, and the polyol preferably includes one or more of glycerol, pentaerythritol, trimethylolpropane, triethanolamine, xylitol, and sorbitol; the diol preferably includes one or more of polyethylene glycol, polytetrahydrofuran glycol, polycarbonate diol, and polycaprolactone diol. In this invention, the organic solvent is preferably dichloromethane. In this invention, the molar ratio of the hydroxyl group in the polyol to the isocyanate group (-NCO) in the diisocyanate is preferably (0.5-2):11, and can be 0.5:11, 1:11, 1.5:11, or 2:11; the molar ratio of the hydroxyl group in the diol to the isocyanate group in the diisocyanate is preferably (2-8):11, and can be 2:11, 3:11, 4:11, 5:11, 6:11, 7:11, or 8:11. In this invention, the polyol serves as a crosslinking agent, and the diol serves as a chain extender.

[0034] In this invention, the preferred method for mixing the polyol, diol, diisocyanate, and organic solvent is stirring, wherein the stirring is performed until all components are uniformly mixed. In this invention, the solid content of the mixture obtained by mixing the polyol, diol, diisocyanate, and organic solvent is preferably 30 wt%.

[0035] In this invention, the temperature of the hydroxyisocyanate esterification reaction is preferably 30-150°C, more preferably 40-100°C, and even more preferably 50-60°C, and the time is preferably 1-8 hours, more preferably 5-6 hours.

[0036] Following the hydroxyisocyanate reaction, no post-treatment is required; ethyl 2-(tert-butylamino)methacrylate is directly added to the resulting product for aminoisocyanate reaction. In this invention, the molar ratio of the amino group in the ethyl 2-(tert-butylamino)methacrylate to the isocyanate group in the diisocyanate is preferably (3–8.5):11, and can be 3:11, 4:11, 5:11, 6:11, 7:11, 8:11, or 8.5:11. In this invention, the temperature of the aminoisocyanate reaction is preferably 0–100°C, more preferably 20–80°C, and even more preferably 50–60°C; the time is preferably 0.5–5 h, more preferably 1–3 h, and even more preferably 2 h. After the aminoisocyanate reaction is completed, the organic solvent is preferably removed by rotary evaporation to obtain a polyurethane-type propylene ester prepolymer containing dynamic tert-butylurea bonds.

[0037] After obtaining a polyurethane-type propylene ester prepolymer containing dynamic tert-butylurea bonds, the present invention mixes the polyurethane-type propylene ester prepolymer containing dynamic tert-butylurea bonds with a diluent monomer and a photoinitiator to obtain a photocurable resin (or photosensitive resin).

[0038] In this invention, the diluent monomer is grafted with an ATRP (Surface-Initiated Atom Transfer Radical Polymerization, i.e., SI-ATRP) initiator (in embodiments of this invention, the diluent monomer grafted with the ATRP initiator is also referred to as a diluent monomer containing the SI-ATRP initiator). In this invention, the diluent monomer is preferably obtained by a nucleophilic substitution reaction between an ATRP initiator and a monomer; the ATRP initiator is preferably 2-bromoisobutyryl bromide, and the monomer preferably includes one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, allyl alcohol, and methacryl alcohol; the molar ratio of the ATRP initiator to the monomer is preferably 1.1:1. In this invention, the ATRP initiator, monomer, acid-binding agent, and organic solvent are preferably mixed to carry out the nucleophilic substitution reaction; the acid-binding agent is preferably triethylamine, and the molar ratio of the acid-binding agent to the ATRP initiator is preferably 1:1; the organic solvent is preferably dichloromethane, and the solid content of the resulting mixture is preferably 10 wt%. In this invention, the nucleophilic substitution reaction preferably includes a sequential ice bath reaction and a room temperature reaction, wherein the ice bath reaction is preferably carried out for 2 hours and the room temperature reaction is preferably carried out for 4 hours. After the nucleophilic substitution reaction is completed, the resulting reaction solution is preferably filtered to remove the white precipitate, the filtrate is washed three times with saturated saline solution, and then subjected to separation, dehydration with anhydrous magnesium sulfate, filtration, and solvent removal by rotary evaporation to obtain the diluted monomer.

[0039] In this invention, the photoinitiator is preferably one or more of Darocur 1173, Irgacure 184, Irgacure 651 and Irgacure 369.

[0040] In this invention, the mass of the diluted monomer is preferably 10-40% of the mass of the photocurable resin, more preferably 15-25%, and even more preferably 18-20%; the mass of the photoinitiator is preferably 0.5-3% of the mass of the photocurable resin, more preferably 1-2%.

[0041] The present invention does not have any special requirements for the method of mixing the polyurethane-type propylene ester prepolymer containing dynamic tert-butylurea bonds with the diluted monomer and photoinitiator, as long as the mixing is uniform.

[0042] After obtaining the photocurable resin, the present invention performs photocuring on the photocurable resin to obtain a polyurethane elastomer containing tert-butylurea bonds and ATRP initiator.

[0043] In this invention, the photocuring is preferably UV curing, specifically involving pouring the photocurable resin into a polytetrafluoroethylene mold for UV curing. In this invention, the UV curing light intensity is preferably 10–100 mW / cm². 2 More preferably 80–100 mW / cm 2 The light exposure time (i.e., curing time) is preferably 2 to 30 minutes, more preferably 10 to 15 minutes.

[0044] After obtaining the polyurethane elastomer containing tert-butylurea bonds and ATRP initiator, the present invention sequentially performs crushing, polyelectrolyte brush grafting and hot pressing on the polyurethane elastomer containing tert-butylurea bonds and ATRP initiator. The sequential crushing, polyelectrolyte brush grafting and hot pressing operations are repeated to obtain the hydrophilic lubricating zwitterionic polyurethane.

[0045] In this invention, the pulverization is preferably carried out by using a pulverizer to pulverize the polyurethane elastomer containing tert-butylurea bonds and ATRP initiator into fine particles with a particle size of less than 1 mm.

[0046] In this invention, the polyelectrolyte brush is preferably one or more of the following: potassium propyl 3-sulfonate polymethacrylate, poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride, poly(N-isopropylacrylamide), poly(2-acrylamide-2-methylpropanesulfonic acid), poly(2-methacryloyloxyethyl phosphocholine), and polysulfonate betaine methacrylate.

[0047] In this invention, the preferred specific operation for the polyelectrolyte brush grafting is as follows:

[0048] A zwitterionic monomer solution is obtained by mixing water, alcohol solvent, hydrophilic alkenyl monomer, catalyst, ligand and reducing agent.

[0049] The polyurethane elastomer particles obtained after pulverization are immersed in the zwitterionic monomer solution, and polyelectrolyte brushes are grafted onto the surface of the polyurethane elastomer particles by SI-ATRP reaction.

[0050] In this invention, the water is preferably deionized water; the alcohol solvent is preferably methanol; the hydrophilic alkenyl monomer is preferably one or more of potassium propyl 3-sulfonate methacrylate, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, N-isopropylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, 2-methacryloyloxyethyl phosphoric acid choline, and sulfobetaine methacrylate; the catalyst is preferably copper chloride dihydrate; the ligand is preferably pentamethyldiethylenetriamine; and the reducing agent is preferably vitamin C. In this invention, the preferred ratio of water, alcohol solvent, hydrophilic alkenyl monomer, catalyst, ligand, and reducing agent is 40 mL:40 mL:40 g:0.24 g:0.244 g:2.48 g. In this invention, the preferred method for mixing the water, alcohol solvent, hydrophilic alkenyl monomer, catalyst, ligand, and reducing agent is stirring, with the stirring aimed at achieving uniform mixing of all components. In this invention, the zwitterionic monomer solution is preferably deoxygenated before use. In this invention, the soaking time (i.e., the SI-ATRP reaction time) is preferably 6 to 18 hours, more preferably 10 to 12 hours, and the soaking can be carried out at room temperature.

[0051] In this invention, the pressure of the single hot-pressing treatment is preferably 2-15 MPa, more preferably 4-12 MPa, and even more preferably 5-10 MPa; the temperature is preferably 80-180°C, more preferably 100-150°C, and even more preferably 120-140°C; the time is preferably 10-60 min, and even more preferably 30-40 min. The hot-pressing treatment is preferably carried out in a flat vulcanizing machine. After the hot-pressing treatment, a uniform and transparent zwitterionic polyurethane film is formed.

[0052] In this invention, the operations of sequentially crushing, polyelectrolyte brush grafting, and hot pressing are repeated; the number of repetitions is ≥0. The polyurethane elastomer synthesized by this invention has good recyclability, mainly attributed to the tert-butylurea (sterically hindered urea) structure formed by diisocyanate and ethyl 2-(tert-butylamino)methacrylate. This structure can rapidly break and recombine during heating and cooling, thus endowing the material with good dynamic recombination properties. This invention enables controllable adjustment of the mechanical and hydrophilic lubricating properties of zwitterionic polyurethane by the number of repetitions of the above-mentioned crushing, polyelectrolyte brush grafting, and hot pressing (which can be called the number of hot pressing recycling). Specifically, different numbers of hot pressing recycling result in different mechanical properties of the zwitterionic polyurethane; the more hot pressing recycling, the higher the polyelectrolyte brush content, thus affecting the hydrophilic lubricating properties of the zwitterionic polyurethane. In the embodiments of this invention, the specific number of repetitions of the sequential crushing, polyelectrolyte brush grafting, and hot pressing operations is 1, 2, or 3. This invention involves repeatedly crushing polyurethane elastomer into fine particles, then grafting polymer brushes onto the surface of the particles, and finally hot-pressing them to form a polyurethane body and surface containing a high content of polyelectrolyte brushes.

[0053] This invention provides a hydrophilic and lubricating zwitterionic polyurethane prepared by the method described above. Starting from the molecular structure design of polyurethane, this invention develops a new zwitterionic polyurethane with controllable mechanical and hydrophilic lubricating properties.

[0054] This invention provides the application of the hydrophilic lubricating zwitterionic polyurethane described above in the preparation of implantable medical devices. The hydrophilic lubricating zwitterionic polyurethane provided by this invention has a high content of polyelectrolyte brushes, with a high content of polyelectrolyte brushes in both the body and surface, and possesses stable and excellent hydrophilic lubrication properties, making it promising for widespread application in the field of implantable medical devices.

[0055] To further illustrate the present invention, the method for preparing hydrophilic lubricating zwitterionic polyurethane through continuous dynamic recombination, the zwitterionic polyurethane and its applications provided by the present invention are described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] A method for preparing hydrophilic lubricating zwitterionic polyurethane through continuous dynamic recombination, comprising the following steps:

[0058] (1) Glycerol (with a molar ratio of hydroxyl to -NCO of 1:11), polytetrahydrofuran glycol (number average molecular weight of 2000, with a molar ratio of hydroxyl to -NCO of 4:11), isophorone diisocyanate, and dichloromethane solvent (solid content of 30wt%) were added to a reactor. After stirring evenly, the mixture was heated to 50°C and reacted for 5 hours. Subsequently, ethyl 2-(tert-butylamino)methacrylate (with a molar ratio of amino to -NCO of 6:11) was added to the above container, and the reaction was continued at 50°C for 2 hours. After the reaction was completed, the dichloromethane solvent was removed by rotary evaporation to obtain a polyurethane-type propylene ester prepolymer containing dynamic tert-butylurea bonds.

[0059] (2) A diluted monomer containing the SI-ATRP initiator was prepared by nucleophilic substitution reaction of hydroxyethyl acrylate and 2-bromoisobutyryl bromide in dichloromethane solvent and triethylamine acid-binding agent. The molar ratio of 2-bromoisobutyryl bromide, hydroxyethyl acrylate, and triethylamine was 1.1:1:1.1, the solid content of the system was 10 wt%, and the nucleophilic substitution reaction conditions were: ice bath reaction for 2 h, and room temperature reaction for 4 h. After the reaction was completed, the white precipitate was removed by filtration, the filtrate was washed three times with saturated brine, and then separated by liquid-liquid extraction, dehydration with anhydrous magnesium sulfate, filtration, and rotary evaporation to remove the dichloromethane solvent, yielding a pale yellow diluted monomer containing the SI-ATRP initiator.

[0060] (3) The polyurethane-type propylene ester prepolymer synthesized in step (1), the diluted monomer synthesized in step (2) and the photoinitiator Darocur 1173 are uniformly mixed to obtain a photosensitive resin; wherein, the mass of the prepolymer is 80% of the total mass of the photosensitive resin, the mass of the diluted monomer is 18% of the total mass of the photosensitive resin, and the mass of the photoinitiator is 2% of the total mass of the photosensitive resin.

[0061] (4) Pour the photosensitive resin obtained in step (3) into a polytetrafluoroethylene mold and cure it under UV light (light intensity 100mW / cm). 2 A polyurethane elastomer containing both dynamic tert-butylurea bonds and an ATRP initiator was obtained by irradiation for 10 min.

[0062] (5) Add 40 mL of deionized water, 40 mL of methanol, 40 g of sulfonated betaine methacrylate, 0.24 g of copper chloride dihydrate, 0.244 g of pentamethyldiethylenetriamine, and 2.48 g of vitamin C to a glass bottle, stir well, and obtain an amphoteric monomer solution.

[0063] (6) The polyurethane elastomer synthesized in step (4) is crushed into fine particles (<1mm) by a pulverizer, and then soaked in the deoxygenated zwitterionic monomer solution synthesized in step (5). After 12h of SI-ATRP reaction, polyelectrolyte brushes are grafted onto its surface.

[0064] (7) The polyelectrolyte-modified polyurethane particles obtained in step (6) are hot-pressed using a flat vulcanizing machine (hot pressing conditions: pressure 10MPa, temperature 140℃, time 30min) to obtain a uniform transparent zwitterionic polyurethane film.

[0065] (8) Steps (6) and (7) are repeated continuously. One step (6) and (7) is one operation. The total number of times this operation is performed is 1, 2, 3 and 4 times respectively, and finally zwitterionic polyurethane with high content of polyelectrolyte brush is obtained.

[0066] The performance of the zwitterionic polyurethane of Example 1 was tested using the following method:

[0067] 1) Mechanical property testing: The tensile strength of the zwitterionic polyurethane obtained after each recycling and reprocessing was measured using a universal testing machine.

[0068] Figure 1 The tensile strength of the zwitterionic polyurethane obtained under different cycle periods in step (8) of Example 1 is shown. Figure 1 In the original text, "Original" represents the polyurethane elastomer synthesized in step (4), and "1st," "2nd," "3rd," and "4th" represent the operations in steps (6) and (7) being performed 1, 2, 3, and 4 times, respectively. Figure 1 It can be seen that as the number of cycles increases, the tensile strength and fracture strain of the obtained zwitterionic polyurethane continuously decrease. This is mainly because the recycling and reprocessing process destroys the original cross-linked network structure of the polymer.

[0069] 2) Hydrophilicity test: The water contact angle of the zwitterionic polyurethane obtained after each recycling and reprocessing was measured using a contact angle meter.

[0070] Figure 2 The water contact angle of the zwitterionic polyurethane obtained under different cycle periods in step (8) of Example 1. Figure 2 It can be seen that as the number of cycles increases, the water contact angle of the obtained zwitterionic polyurethane first decreases and then increases, reaching its lowest value after three operations in steps (6) and (7). This is mainly because the content of polyelectrolyte brush in the zwitterionic polyurethane increases with the number of cycles in the initial stage of the cycle, thereby improving the hydrophilicity of the material; continued cycling leads to the destruction of the original cross-linked network and surface structure of the material, thereby reducing the hydrophilicity.

[0071] 3) Friction test: The zwitterionic polyurethane obtained in step (8) of Example 1 was subjected to friction test using a CSM friction tester. The friction test conditions were as follows: the friction pair was a polydimethylsiloxane (PDMS) elastomer ball with a diameter of 6 mm, the sliding frequency was 2 Hz, the applied load was 1 N, the lubricant was water, the friction stroke was 6 mm, and 2000 reciprocating friction tests were performed.

[0072] Figure 3 The tribological properties of the zwitterionic polyurethane obtained under different cycle periods in step (8) of Example 1 are shown. Figure 3 It can be seen that as the number of cycles increases, the coefficient of friction (COF) of the obtained zwitterionic polyurethane first decreases and then increases, reaching its lowest value after three operations in steps (6) and (7). The specific reason is the same as the trend of water contact angle change mentioned above.

[0073] 4) Sulfur distribution test: The sulfur distribution on the surface and cross-section of the zwitterionic polyurethane obtained in step (8) of Example 1 was determined by field emission scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS).

[0074] Figure 4 The sulfur element (derived from the grafted sulfonate betaine methacrylate) distribution on the surface and cross-section of the zwitterionic polyurethane obtained under different cycle periods in step (8) of Example 1 is shown. Figure 4 The top row of images shows the sulfur distribution on the surface, and the bottom row shows the sulfur distribution across the cross-section. Figure 4 It can be seen that as the number of cycles increases, the sulfur content of the resulting zwitterionic polyurethane increases and the distribution becomes more uniform.

[0075] Example 2

[0076] The zwitterionic polyurethane was prepared according to the method of Example 1, except that in step (5), sulfonated betaine methacrylate was replaced with potassium propyl methacrylate 3-sulfonate.

[0077] Example 3

[0078] The zwitterionic polyurethane was prepared according to the method of Example 1, except that in step (5), sulfonated betaine methacrylate was replaced with [2-(methacryloyloxy)ethyl]trimethylammonium chloride.

[0079] Example 4

[0080] The zwitterionic polyurethane was prepared according to the method of Example 1, except that in step (5), sulfonated betaine methacrylate was replaced with N-isopropylacrylamide.

[0081] Example 5

[0082] The zwitterionic polyurethane was prepared according to the method of Example 1, except that in step (5), sulfonated betaine methacrylate was replaced with 2-acrylamide-2-methylpropanesulfonic acid.

[0083] The tensile strength, water contact angle and coefficient of friction of the zwitterionic polyurethanes obtained in Examples 1 to 5 (the operations of steps (6) and (7) were performed 4 times) are shown in Table 1. The test conditions for the coefficient of friction in Table 1 are the same as those for the friction test in step 3) above.

[0084] Table 1. Tensile strength, water contact angle, and coefficient of friction of samples from Examples 1-5

[0085] Example Tensile strength (MPa) Water contact angle (o) Friction coefficient Example 1 2.68 37.58 0.138 Example 2 2.54 40.23 0.147 Example 3 1.89 42.65 0.156 Example 4 3.21 78.56 0.452 Example 5 3.02 47.89 0.371

[0086] Comparative Example 1

[0087] Amphoteric polyurethane was prepared according to the method of Example 1, except that in step (1), the molar ratio of hydroxyl groups to -NCO in polytetrahydrofuran diol was 8:11, and the molar ratio of amino groups to -NCO in ethyl 2-(tert-butylamino)methacrylate was 2:11. The polyurethane elastomer obtained in this comparative example had a relatively low content of dynamic tert-butylurea bonds, and the sample could not be recycled and reprocessed by hot pressing.

[0088] Comparative Example 2

[0089] Amphoteric polyurethane was prepared according to the method of Example 1, except that the diluent monomer containing the SI-ATRP initiator in steps (2) and (3) was directly replaced with hydroxyethyl acrylate. Because the polyurethane elastomer obtained in this comparative example does not contain the SI-ATRP initiator, it is impossible to introduce a polyelectrolyte brush onto its surface via the SI-ATRP reaction, nor can an amphoteric polyurethane be obtained through dynamic recombination.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing hydrophilic lubricating zwitterionic polyurethane through continuous dynamic recombination, characterized in that, Includes the following steps: A polyol, a diol, a diisocyanate, and an organic solvent are mixed to undergo a hydroxyisocyanation reaction. The resulting product is then mixed with ethyl 2-(tert-butylamino)methacrylate to undergo an aminoisocyanation reaction, yielding a polyurethane-type propylene ester prepolymer containing dynamic tert-butylurea bonds. The polyol contains three or more hydroxyl groups. The molar ratio of hydroxyl groups in the polyol to isocyanates in the diisocyanate is (0.5~2):

11. The molar ratio of hydroxyl groups in the diol to isocyanates in the diisocyanate is (2~8):

11. The molar ratio of amino groups in the ethyl 2-(tert-butylamino)methacrylate to isocyanates in the diisocyanate is (3~8.5):

11. The polyurethane-type acrylic ester prepolymer containing dynamic tert-butylurea bonds is mixed with a diluent monomer and a photoinitiator to obtain a photocurable resin; the diluent monomer is grafted with an ATRP initiator; the diluent monomer is obtained by a nucleophilic substitution reaction between the ATRP initiator and the monomer, wherein the ATRP initiator is 2-bromoisobutyryl bromide, and the monomer includes one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, allyl alcohol, and methacryl alcohol; the mass of the diluent monomer is 10-40% of the mass of the photocurable resin. The photocurable resin is photocured to obtain a polyurethane elastomer containing tert-butylurea bonds and an ATRP initiator; The polyurethane elastomer containing tert-butylurea bonds and ATRP initiator is subjected to a series of operations including pulverization, polyelectrolyte brush grafting, and hot pressing. These operations are repeated to obtain the hydrophilic lubricating zwitterionic polyurethane. The number of repetitions is ≥0. The polyelectrolyte brush is one or more of the following: potassium propyl 3-sulfonate polymethacrylate, poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride, poly(N-isopropylacrylamide), poly(2-acrylamide-2-methylpropanesulfonic acid), poly(2-methacryloyloxyethyl phosphocholine), and polysulfonate betaine methacrylate.

2. The method according to claim 1, characterized in that, The diisocyanate includes one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate; the polyol includes one or more of glycerol, pentaerythritol, trimethylolpropane, triethanolamine, xylitol, and sorbitol; the diol includes one or more of polyethylene glycol, polytetrahydrofuran glycol, polycarbonate diol, and polycaprolactone diol.

3. The method according to claim 1, characterized in that, The hydroxyisocyanate reaction is carried out at a temperature of 30~150℃ for 1~8h; the aminoisocyanate reaction is carried out at a temperature of 0~100℃ for 0.5~5h.

4. The method according to claim 1, characterized in that, The mass of the photoinitiator is 0.5-3% of the mass of the photocurable resin.

5. The method according to claim 1, characterized in that, The pressure for a single hot pressing treatment is 2~15MPa, the temperature is 80~180℃, and the time is 10~60min.

6. The hydrophilic lubricating zwitterionic polyurethane prepared by the method according to any one of claims 1 to 5.

7. The application of the hydrophilic lubricating zwitterionic polyurethane of claim 6 in the preparation of implantable medical devices.

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