Preparation And Properties Of Biodegradable Two-component Polyurethane Adhesive And Photopolymerized Hydrogel

The medical polyurethane materials have been used in wide range of applications,owning to their good biotoxicity,biodegradability,blood compatibility,biocompatibility,and excellent mechanical properties.Contrary tothe traditional two-component polyurethane adhesive and medical hydrogel were developed for the improvement of medical polyurethane adhesive and hydrogel.Ring-opening polymerization was carried out by using polyether(poly(ethylene oxide)-b-(propylene oxide),PPEO)with different arms as the main material,and using L-lactide(L-LA)or ε-caprolactone(ε-CL)as monomers under the catalysis of stannous octoate.Then the hydroxyl prepolymer contained polyesters segments was end capped with the hexamethylene diisocyanate(HDI)to get a prepolymerwith terminal-NCO groups(-NCO,B component),which can react with the aspartic acid ester compounds(ASP,A component)to obtain a two-component polyurethane adhesive.The structures andproperties of hydroxyl prepolymer,isocyanate prepolymer,aspartate compound and polyurethane adhesivewere characterized by NMR,FT-IR,HR-TOF-MS,TGA,DSC and so on.The optimum reaction conditions were obtained by di-n-butylamine method: the molar ratio of-NCO:-OH group was 3,the reaction time was 3.5 ~ 4 h.Through the study of different proportions of A and B components,the index of the-NCO was 1.2,the obtained adhesive had a shorter(2 minutes)dry time and a curing time(6 minutes).At the same time,it also had a good mechanical performance,bond strength(74 N·cm-2),tensile elongation at break(60%),and tensile strength at break(2.8 MPa).The result of the polyurethane adhesive analysized bythermal properties revealed that there were two glass transition temperatures,which proved that there weremicrophase separations in its structures.There were three thermal decomposition stages in the thermal stability experiment: the first stage was the decomposition of ureaand urethane groups,the second stage was the decomposition of ester groups,the third stage was attributed to soft segment ether groupdecomposition.The results of the polyurethane adhesive film contact angle and in vitro degradation analysis showed that the more proportion of ester groups in the polyurethane adhesive,the faster of the degradation rate.In result,we can control the ester groups to prepare the different parts of the required adhesive.N-arm-poly(ethylene glycol)-polycaprolactone(n-arm-PEG-PCL,n=2,3,4)was synthesized via bulk ring-opening polymerization with n-arm-PEGas initiator,ε-caprolactone(ε-CL)as monomer and stannous octoate as catalyst,then reacted with acryloyl chloride to obtain the acrylate-terminated n-arm-PEG-PCL prepolymer(n-arm-PEG-PCL-AC).The chemical structures of the polymers were confirmed by FT-IR and1 H NMR.The photosensitive properties of the prepolymeraqueous solution were researched under UV light,and the results showed that the gelation time decreased with theincreasment of copolymer concentration and arms.The results of in vitrodegradation indicated that the degradation rate of the hydrogel after polyester modification increased obviously,and decreased with the increasing arm of prepolymer.In vitro drug release studies were carried out using ceftibuten as a model drug,the results indicated that drug release rate was consistent with the degradation rate and the hydrogel was an effective system for achieving long-sustained(15-30days)controlled release.Also,the pH-sensitive hydrogels were prepared by adding acrylic acid to the prepolymeraqueous solution,and the swelling ratio and drug release rate of the pH-sensitive hydrogels increased obviously with increasement of pH value.