原位聚合法制备具有温敏PNIPAM壳的核-壳结构聚合物纳米微球的研究

结合大分子自组装和原位自由基聚合方法,采用油溶性引发剂偶氮二异丁腈(AIBN),在聚(ε-已内酯)(PCL)纳米粒子表面引发聚合单体N-异丙基丙烯酰胺(NIPAM)和交联剂亚甲基双(丙烯酰胺)(MBA),制备得到了核-壳结构的PCL/PNIPAM聚合物纳米微球.系统研究了单体和交联剂用量、壳层目标交联度、初始PCL/DMF溶液的浓度及引发剂AIBN含量4个反应参数对核-壳结构PCL/PNIPAM纳米微球的PNIPAM壳层得率、微球尺寸、温敏性能及电镜形貌的影响.结果表明,在制备核-壳结构PCL/PNIPAM纳米微球的反应过程中,PCL粒子表面的聚合和水中的聚合二者之间相互竞争.适当增加引发剂AIBN的添加量,有利于制备得到核/壳比例可控的PCL/PNIPAM纳米微球;交联剂MBA较高的反应活性导致形成了非均匀交联的PNIPAM壳层.

PREPARATION OF THERMO-SENSITIVE CORE-SHELL POLYMERIC NANOSPHERES via "in situ" POLYMERIZATION METHOD

A new method,in which the polymerization of the shell component accompanies the self-assembly of macromolecules,was proposed to prepare core-shell nanospheres.Based on this in situ polymerization method,thermo-sensitive core-shell nanospheres with poly(ε-caprolactone)(PCL)core and poly(N-isopropylacrylamide)(PNIPAM)shell were prepared from monomer NIPAM and crosslinker methylene bisacrylamide(MBA).The influences of the total amount of monomer and crosslinker,the target crosslinking degree of PNIPAM shell,the initial concentration of PCL in DMF and the content of initiator AIBN on the yield of PNIPAM shell,the size,the thermo-sensitive behavior and the morphology of PCL/PNIPAM core-shell nanospheres were studied in details.The results show that during the preparation of PCL/PNIPAM core-shell nanospheres,the polymerization on the surface of PCL nanoparticles competes with that in the water.Increasing the amount of initiator AIBN properly is favorable to the preparation of PCL/PNIPAM core-shell nanospheres with controlled core/shell weight ratio.In addition,the relatively higher reactivity of cross-linker MBA compared with NIPAM leads to the formation of unevenly crosslinked PNIPAM shells.