| Biomedical polymer materials have broad applications in biological system,such as the treatment of disease,drug delivery systems,the repair and replace of biological tissues and organs.Among them,biodegradable aliphatic polycarbonate containing functional groups have attracted more and more attention.As known,cholesterol is a fundamental composition of anmimals,its derivatives can be used as bioactive liquid crystal(LC)units because of good biological compatibility.In this paper,the main aim is to synthesize and characterize new biodegradable polymer materials with both biocompatible and the advantage of LC,and then self-assembly properties,drug delivery properties and degradation properties of the obtained material were studied to explore the potential application.In the second chapter,the compound 5-benzyloxy-trimethylene carbonate(BTMC)was first synthesized.Secondly,amphiphilic polymer mPEG43-b-PBTMC31 was synthesized by ring-opening polymerization of BTMC using poly(ethylene glycol)monomethyl ether(mPEG)as an initiator and Sn(Oct)2 as catalyst,and then amphiphilic block copolymer mPEG43-bP(BTMC20-TMC20)was synthesized by the copolymerization of BTMC and TMC using mPEG as initiator.The protective benzyl groups in polymer chains were removed by catalytic hydrogenolysis Pd/C and Pd(OH)2/C as catalyst under hydrogen atmosphere to obtain mPEG43b-PHTMC31 and mPEG43-b-P(HTMC20-TMC20).Finally,cholesteryl derivatives 6cholesteroxy-6-oxocaproicacid(C)was synthesized,and then C was reacted with mPEG43-bPHTMC31 and mPEG43-b-P(HTMC20-TMC20),respectively,to obtain four new amphiphilic graft copolymers mPEG43-b-P[(TMC-C)28-HTMC3](P,),mPEG43-b-P[(TMC-C)20-TMC20](P2-1),mPEG43-b-P[(TMC-C)15-HTMC5-TMC20](P2-0.75)and mPEG43-b-P[(TMC-C),2HTMC8-TMC20](P2-0.5)?The structure of cholesteryl derivatives and copolymers obtained in this study were characterized with FT-IR and 1H NMR,and then thermal properties and optical textures were characterized by DSC,TGA,POM and XRD.The results showed that C exhibited typical oily texture and focal conic texture of cholesteric phase on heating and cooling cycles,and P1,P2-1,P2-0.75,P2-0.5 exhibited focal conic texture of semctic phase.In addition,the corresponding melting temperature(Tm),isotropic temperature(Ti)and decomposition temperature(Td)increased with an increase of LC units in the copolymer.In the third chapter,the self-assembly behavior of amphiphilic block copolymers(P1,P2-1,P2-0.75,P2-0.5)were studied.The influence of solution concentration,pH value and molecular structure on self-assembly behavior of the copolymers was discussed.The results showed that the assembly process was faster and the aggregate particle size was larger when the polymer solution concentration was higher.The assembly behavior had a pH-responsive and quickly self-assemble happened under the condition of weak acid.Comparing the self-assembly process of polymers P2-1,P2-0.75,P2-0.5,the more content of LC units,the faster self-assembly process,and the smaller particle size formed.The reason was that the LC order could hasten the form of the self-assembly,and assembled sphere were more tightly packed,and form smaller particle size.In the fourth chapter,the self-assembled microsphere of the loaded doxorubicin(DOX)for amphiphilic block copolymers(P1,P2-1,P2-0.75,P2-0.5)was discussed.P1-DOX and P2-1-DOX all had a pH-responsive,and DOX could be released quickly in weak acid environment.The existence of hydroxyl groups in the copolymers had certain binding effect on DOX for P2-1,P2-0.75,P2-0.5.In addition,the existence of LC units was beneficial to reduce the microspheres particle size.In addition,the hydrolysis and enzymolysis experiments of polymer P1 film were carried out.The results showed that P1 film displayed hydrophobic property and its hadrolysis process was slow.Because enzyme molecular weight was bigger,and harder to attack the main chain of the polycarbonate,enzyme degradation rate was more slowly.Another reason was that this emzyme was non-sensitive to P1. |
PDF Full Text Request