Switching the inside and the outside of aggregates of water-soluble block copolymers with double thermoresponsivity
Switching the inside and the outside of aggregates of water-soluble block copolymers with double thermoresponsivity
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DOI：
10.1021/ja012167d
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发表时间：
2002-04-10
影响因子：
15
通讯作者：
Laschewsky, A
中科院分区：
文献类型：
--
作者：
Arotçaréna, M;Heise, B;Laschewsky, A
以非离子单体N-异丙基丙烯酰胺(NIPA)和两性离子单体3-[N-(3-甲基丙烯酰氨基丙基)-N,N-二甲基]氨丙磺酸盐(SPP)为原料，通过RAFT工艺连续自由基聚合制备了水溶性嵌段共聚物。这种具有两个亲水嵌段的嵌段共聚物在水中表现出双重热响应行为：聚-NIPA嵌段表现出较低的临界溶解温度，而聚-SPP嵌段表现出较高的临界溶解温度。适当设计嵌段长度可使嵌段共聚物在 0 至 100 摄氏度的整个温度范围内保持溶液状态。这些聚合物的两种嵌段在中间温度下都溶解在水中，而在高温下，聚-NIPA嵌段形成胶体疏水缔合体，其通过聚-SPP嵌段保持在溶液中，而在低温下，聚-SPP嵌段形成胶体极性聚集体，其通过聚-NIPA嵌段保持在溶液中。这样，可以在水中制备可逆转换的胶体聚集体，并且无需任何添加剂，它们的“内部”到“外部”，反之亦然。聚集体提供了不同特征的微域和表面，可以通过简单的热刺激来控制。
Water-soluble block copolymers were prepared from the nonionic monomer N-isopropylacrylamide (NIPA) and the zwitterionic monomer 3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]ammoniopropane sulfonate (SPP) by sequential free radical polymerization via the RAFT process. Such block copolymers with two hydrophilic blocks exhibit double thermoresponsive behavior in water: the poly-NIPA block shows a lower critical solution temperature, whereas the poly-SPP block exhibits an upper critical solution temperature. Appropriate design of the block lengths leads to block copolymers which stay in solution in the full temperature range between 0 and 100 degreesC. Both blocks of these polymers dissolve in water at intermediate temperatures, whereas at high temperatures, the poly-NIPA block forms colloidal hydrophobic associates that are kept in solution by the poly-SPP block, and at low temperatures, the poly-SPP block forms colloidal polar aggregates that are kept in solution by the poly-NIPA block. In this way, colloidal aggregates which switch reversibly can be prepared in water, and without any additive, their "inside" to the "outside", and vice versa. The aggregates provide microdomains and surfaces of different character, which can be controlled by a simple thermal stimulus.