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在固定化脂肪酶Novozym 435催化下,分别以2-巯基乙醇、单甲氧基聚乙二醇(MPEG)为引发剂引发ε-己内酯(ε-CL)开环聚合制备了末端巯基化的聚己内酯(HS-PCL)和两亲性嵌段共聚物聚乙二醇-b-聚己内酯(PEG-b-PCL);用IR、1H-NMR、GPC对聚合产物结构进行了表征;研究了引发剂/单体投料比、聚合时间和温度对聚合产物的影响;考察了HS-PCL的巯基在二甲亚砜、四氢呋喃、丙酮中氧化生成二硫键的活性;用动态激光光散射法和1H-NMR研究了PEG-b-PCL在水溶液中自组装体的尺寸和结构.结果表明,合成产物具有预期结构;固定化脂肪酶Novozym 435具有较高催化活性,在70℃下催化ε-CL本体聚合,2h的单体转化率达到80%;2-巯基乙醇和MPEG都可有效引发ε-CL开环聚合;HS-PCL在大气氛下,在所研究的介质中,于一定温度放置一定时间后,样品的数均分子量增大,但未达到原分子量的2倍,表明一部分HS-PCL的巯基发生氧化反应生成了PCL-S-S-PCL;PEG-b-PCL在水溶液中自组装形成具有核壳结构的胶束,随共聚物中[CL]/[EO]由0.23增大到1.70,胶束粒径由64nm增大到122nm.
After the immobilized lipase Novozym 435 catalyzed ring-opening polymerization of ε-caprolactone (ε-CL) with 2-mercaptoethanol and monomethoxypolyethylene glycol (MPEG) as initiators, Polycaprolactone (HS-PCL) and amphiphilic block copolymer polyethylene glycol-b-polycaprolactone (PEG-b-PCL); the polymerization product structure was characterized by IR, 1H- The effects of initiator / monomer ratio, polymerization time and temperature on the polymerization products were investigated. The activity of sulfhydryl groups of HS-PCL in dimethylsulfoxide, tetrahydrofuran and acetone was investigated. The results showed that the synthesized product had the expected structure. The immobilized lipase Novozym 435 had a high catalytic activity at 70 ℃ Under the catalysis of ε-CL bulk polymerization, the monomer conversion reached 80% after 2 hours; 2-mercaptoethanol and MPEG could effectively initiate the ring-opening polymerization of ε-CL; Under the atmosphere of HS-PCL, After being allowed to stand at a certain temperature for a certain period of time, the number average molecular weight of the sample increased but did not reach twice the original molecular weight, indicating that a part of thiol groups of HS-PCL occurred PCL-SS-PCL was formed by oxidation reaction. PEG-b-PCL self-assembled in aqueous solution to form micelles with core-shell structure. With the increase of [CL] / [EO] from 0.23 to 1.70 in the copolymer, The diameter increased from 64nm to 122nm.