PDF(Pubmed)
Abstract：
Thermo-responsive diblock copolymer, poly(N-isopropylacrylamide)-block-poly(N-vinylisobutyramide) was synthesized via switchable reversible addition-fragmentation chain transfer (RAFT) polymerization and its thermal transition behavior was studied. Poly(N-vinylisobutyramide) (PNVIBA), a structural isomer of poly(N-isopropylacrylamide) (PNIPAM) shows a thermo-response character but with a higher lower critical solution temperature (LCST) than PNIPAM. The chain extension of the PNVIBA block from the PNIPAM block proceeded in a controlled manner with a switchable chain transfer reagent, methyl 2-[methyl(4-pyridinyl)carbamothioylthio]propionate. In an aqueous solution, the diblock copolymer shows a thermo-responsive behavior but with a single LCST close to the LCST of PNVIBA, indicating that the interaction between the PNIPAM segment and the PNVIBA segment leads to cooperative aggregation during the self-assembly induced phase separation of the diblock copolymer in solution. Above the LCST of the PNIPAM block, the polymer chains begin to collapse, forming small aggregates, but further aggregation stumbled due to the PNVIBA segment of the diblock copolymer. However, as the temperature approached the LCST of the PNVIBA block, larger aggregates composed of clusters of small aggregates formed, resulting in an opaque solution.
摘要：
热响应二嵌段共聚物,通过可逆加成-断裂链转移（RAFT）聚合合成了聚（N-异丙基丙烯酰胺）-嵌段-聚（N-乙烯基异丁酰胺），并研究了其热转变行为。聚(N-乙烯基异丁酰胺)(PNVIBA),聚（N-异丙基丙烯酰胺）（PNIPAM）的结构异构体显示出热响应特性，但具有比PNIPAM更低的临界溶解温度（LCST）。PNVIBA嵌段从PNIPAM嵌段的链延伸以可控的方式与可切换的链转移试剂进行，2-[甲基(4-吡啶基)氨基甲硫基]丙酸甲酯。在水溶液中，二嵌段共聚物显示热响应行为，但具有接近PNVIBA的LCST的单个LCST，表明PNIPAM片段和PNVIBA片段之间的相互作用导致溶液中二嵌段共聚物的自组装诱导相分离过程中的协同聚集。在PNIPAM区块的LCST上方，聚合物链开始崩溃，形成小聚集体，但由于二嵌段共聚物的PNVIBA链段,进一步聚集受阻。然而,随着温度接近PNVIBA区块的LCST，由形成的小聚集体簇组成的较大聚集体，导致不透明的解决方案。
