Hales Michelle, Barner-Kowollik Christopher, Davis Thomas P, Stenzel Martina H
Centre for Advanced Macromolecular Design, School of Chemical Engineering and Industrial Chemistry, The University of New South Wales, Sydney, NSW 2052 Australia.
Langmuir. 2004 Dec 7;20(25):10809-17. doi: 10.1021/la0484016.
A polylactide (D,L-PLA) macroRAFT agent was prepared by utilizing a hydroxyl-functional trithiocarbonate as a coinitiator for the ring-opening polymerization. The length of the resultant polymer was controlled by the concentration of the coinitiator leading to the formation of two PLA polymers with M(n) = 12500 g mol(-)(1) (PDI = 1.46) and M(n) = 20500 g mol(-)(1) (PDI = 1.38) each with omega-trithiocarbonate functionality. Chain extension of PLA via the RAFT (free radical) polymerization of N-isopropyl acrylamide (NIPAAm) resulted in the formation of amphiphilic block copolymers with the PNIPAAm block increasing in size with conversion. TEM measurements of the aggregates obtained by self-organization of the block copolymers in aqueous solutions indicated the formation of vesicles. The sizes of these aggregates were influenced by the ratio of both blocks and the molecular weight of each block. The lower critical solution temperature (LCST) of the block copolymer was largely unaffected by the size of each block. UV turbidity measurements indicated a higher LCST for the block copolymers than for the corresponding PNIPAAm homopolymers. Stabilization of the vesicles was attained by a cross-linking chain extension of the PNIPAAm block using hexamethylene diacrylate. As the trithiocarbonate group was located between the PLA and PNIPAAm blocks, the chain extension resulted in a cross-linked layer between the core and corona of the vesicles.
通过使用羟基官能化的三硫代碳酸酯作为开环聚合的共引发剂，制备了聚丙交酯（D，L-PLA）大分子RAFT试剂。所得聚合物的长度由共引发剂的浓度控制，从而形成两种具有ω-三硫代碳酸酯官能团的聚丙交酯聚合物，其数均分子量M(n) = 12500 g mol⁻¹（分散度PDI = 1.46）和M(n) = 20500 g mol⁻¹（PDI = 1.38）。通过N-异丙基丙烯酰胺（NIPAAm）的RAFT（自由基）聚合对聚丙交酯进行扩链，导致形成两亲性嵌段共聚物，其中聚N-异丙基丙烯酰胺嵌段的尺寸随转化率增加。对嵌段共聚物在水溶液中自组装得到的聚集体进行透射电子显微镜（TEM）测量表明形成了囊泡。这些聚集体的尺寸受两个嵌段的比例和每个嵌段的分子量影响。嵌段共聚物的低临界溶液温度（LCST）在很大程度上不受每个嵌段尺寸的影响。紫外浊度测量表明，嵌段共聚物的LCST高于相应的聚N-异丙基丙烯酰胺均聚物。通过使用己二酸二烯丙酯对聚N-异丙基丙烯酰胺嵌段进行交联扩链，实现了囊泡的稳定化。由于三硫代碳酸酯基团位于聚丙交酯和聚N-异丙基丙烯酰胺嵌段之间，扩链导致在囊泡的核和冠之间形成交联层。
