Synthesis And Property Of Stimuli-responsive Four-arm Star Polymers

The synthesis and property study of environmental stimuli-responsivecopolymers which have attracted much interest recently. These polymerswhich have intelligent characteristic, can respond to environment changes,such as the changes in pH, temperature, light or ionic strength and so on.The amphiphilic star block copolymers will be widely used in biomedicaland medical sciences in near future. In this dissertation, We synthesizedthree kinds of environmental stimuli-responsive amphiphilic star blockcopolymers and respectively studied these polymers’ environmentalresponse behavior. Then the copolymers’ aggregation behaviors andpotential applications as potential drug carriers were preliminarily studied.In the dissertation, four-arm initiator was synthesized based withpentaerythritol. The main contents of this thesis are presented as below:(1) By atom transfer radical polymerization (ATRP) method, Wesynthesized the amphiphilic four-arm star block copolymersPolystyrene-b-Poly methyl methacrylate dimethyl amino ethyl(PENTA-PS-PDMA). The structure and shape of them were characterizedby~1H NMR, GPC, SEM, and the stimuli-responsive behavior of thecopolymers was investigated by laser light scattering (LLS).(2) The amphiphilic four-arm star block copolymers(PENTA-PS-PDEA) were also synthesized by the ATRP method. Thestructure and shape of these copolymers were studied by~1H NMR, GPC,SEM. The pH-responsive and the aggregation behavior of copolymerswere investigated by LLS.(3) With the same method, the amphiphilic four-arm star blockcopolymers (PENTA-PNIPAM-PS) were obtained by ATRP. The structureand shape of polymers were charactered by~1H NMR, GPC, SEM, TEM.The thermo-responsive and the aggregation behavior of copolymers were investigated by LLS.(4) In the dissertation， the potential applications of three kinds ofcopolymers as drug carriers were tested by a combination of pyrenefluorescent probe technique and pyrene UV spectroscopy.The results show that the﹤R_h﹥of the polymer (PENTA-PS-PDMA)in aqueous solution is changed with the changes in pH and temperature.The result showed that the polymer have temperature-and pH-responsivebehavior. We also studied the synthesis and pH responsiveness of(PENTA-PS-PDEA). Then the size variation of polymers in aqueoussolutions with different pH were characterized by LLS. The tests resultsshowed that this kind of copolymer has pH-responsive behavior. At thesame time, we also studied the aggregation form of the copolymer bychanging the acid and alkaline of solutions. Then the copolymers(PENTA-PNIPAM-PS)’s﹤R_h﹥were also studied by changing thetemperature through LLS. The copolymers could be aggregated to bedifferent shapes by regulating the temperature. At last, we have had apreliminary study about drug encapsulated of the three kinds ofcopolymers.