N-异丙基丙烯酰胺类共聚物温敏性研究

STUDIES ON THERMAL TRANSITION OF N-ISOPROPYLACRYLAMIDE COPOLYMERS

制备了N-异丙基丙烯酰胺(NIPAAm)与N,N-二甲基丙烯酰胺(DMAAm)和/或甲基丙烯酸羟乙酯(HEMA)的二元及三元共聚物,研究了组成和链转移剂用量对共聚物温敏性的影响,并在上述三元共聚物上接枝聚己内酯(PCL)得到温敏性两亲聚合物.结果表明,随着DMAAm增加、HEMA减少或共聚物分子量降低,共聚物的最低临界溶解温度升高,且PCL链段的接枝度和长度对聚合物的温敏性影响明显.

Poly（N-isopropylacrylamide-co-N,N-dimethylacrylamide） （poly（NIPAAm-co-DMAAm））,poly（N-isopropylacrylamide-co-2-hydroxyethyl methacrylate） （poly（NIPAAm-co-HEMA）） and poly（NIPAAm-co-DMAAm-co-HEMA）） were synthesized by free radical solution copolymerization using thioglycol as chain transfer agent.Their compositions,molecular weights and thermal transitions were determined by ^1H-NMR,GPC analysis and lower critical solution temperature （LCST） determination.Poly（NIPAAm-co-DMAAm） showed markedly increase in LCST with incorporation of hydrophilic DMAAm,while the LCST of poly（NIPAAm-co-HEMA） moved to lower temperature in comparison with polyNIPAAm,although HEMA is also a hydrophilic comonomer.It was suggested that the formation of hydrogen bonds between the nitrogen atoms in NIPAAm and the hydroxyls in HEMA invoked the phenomenon.Accordingly,a series of poly（NIPAAm-co-DMAAm-co-HEMA） with LCST of ca. 40℃ were prepared in a similar way.These copolymers containing side hydroxyl groups had been used to initial the ring opening polymerization of caprolactone （CL） and poly（NIPAAm-co-DMAAm-co-HEMA） grafted PCL copolymers were obtained.Preliminary studies showed that LCST of the grafted amphiphilic copolymers shifted to lower values with the introduction of hydrophobic PCL chains onto the hydrophilic backbone.Their thermal sensitivity decreased with the amount and length of side PCL chains being increased.Ideally,thermal sensitive micelles prepared from these amphiphilic copolymers would be good candidates for target or ＂smart＂ drug controlled delivery to treat diseases,such as solid tumor in combination with local hyperthermia therapy.