摘要
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.
Thiol end-functionalized polycaprolactone （HS-PCL） and amphiphilic poly（ethylene glyeol）-b- polycaprolactone （PEG-b-PCL） were synthesized via ring-opening polymerization of e-caprolactone （ε-CL） using Novozym 435 （immobilized form of lipase B from Candida antarctica ） as biocatalyst, and 2-mercaptoethanol and methoxy poly （ethylene glycol ） （MPEG） as initiators, respectively. The structure of the obtained polymers was characterized by means of IR, ^1H-NMR and GPC. The effects of the feed ratio of initiator to CL, polymerization temperature and time on the monomer conversions and molecular weights of polymers were investigated. Oxidation of the thiol end groups of HS-PCL to form disulfide bonds was studied in a series of solvents including DMSO, THF and acetone. The structure and sizes of the copolymer PEG-b-PCL micelles were analyzed by means of DLS and ^1H- NMR. The results showed that the obtained polymers had the expected structure; Novozym 435 had high catalytic activity, for the bulk polymerizaion with 10 wt% Novozym 435, the monomer conversion achieved ca. 80% within 2 h at 70℃ ; 2-mercaptoethanol and MPEG could effectively initiate the ring-opening polymerization of CL; HS-PCL samples were placed in DMSO （or THF or acetone） under ambient atmosphere at a certain temperature, such as 37℃ or 70℃, the molecular weights of the oxidized products increased, but less than 2 times that of HS-PCL, indicating that some HS-PCL molecules were oxidized to form PCL-S-S-PCL. The PEG-b-PCL copolymers could selfassemble into nano-sized micelles composed of hydrophobic PCL core and hydrophilic PEG shell in aqueous solution. The hydrodynamic diameters of micelles varied from 64 nm to 122 nm as the increase of [CL]/[EO] of copolymer from 0.23 to 1.70.
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2009年第8期796-802,共7页
Acta Polymerica Sinica
基金
上海市科委重点项目(项目号08JC1411500)
上海市教委重点项目(项目号09ZZ24)资助
