Surface Activity and Structure of Temperature-Responsive Polymer Surfactants Based on PNIPAm at the Air/Solution Interface.
Surface Activity and Structure of Temperature-Responsive Polymer Surfactants Based on PNIPAm at the Air/Solution Interface.
复制标题
DOI：
10.1021/acs.langmuir.1c00320
复制
发表时间：
2021-04
期刊：
影响因子：
--
通讯作者：
Cuiyun Zhang;Wei Chen;Yongming Hong;Xinping Wang
中科院分区：
文献类型：
--
作者：
Cuiyun Zhang;Wei Chen;Yongming Hong;Xinping Wang
热敏聚合物在刺激响应型表面活性剂的设计中引起了极大的兴趣。本文采用原子转移自由基聚合法(ATRP)合成了不同嵌段长度的聚环氧丙烷-b-聚N-异丙基丙烯酰胺(PPO-b-PNIPAM)。与市售的Pluronic表面活性剂不同，表面张力随浓度的降低出现了四个明显的区段。首先，随着浓度的增加，聚合物的吸附量增加，表面张力急剧下降，直到达到一个平台，这是由于甲基重排造成的。随着PPO-b-PNIPAM吸附量的增加，异丙基发生重排，由平卧构象或水平构象转变为直立构象或垂直构象。这一行为导致了第三部分的表面张力下降，直到达到临界胶束浓度(CMC)。PPO-b-PNIPAM的表面张力是热响应的。除了第一次循环中观察到的滞后外，表面张力在加热和冷却循环中是可逆的。在低浓度下，较高温度下的低表面张力主要是由于甲基的吸附量和有序排列增加所致，而在较高浓度下，异丙基的竖立构象导致了高温下的低表面张力。
Thermally sensitive polymers have attracted tremendous interest in the design of stimulus-responsive surfactants. In this article, poly(propylene oxide)-b-poly(N-isopropylacrylamide) (PPO-b-PNIPAm) with different block lengths of PNIPAm was synthesized through atom transfer radical polymerization (ATRP). Different from commercial Pluronic surfactants, four distinct sections appeared in the decrease of surface tension with concentration. First, with increasing concentration, the amount of adsorbed polymers increased and the surface tension decreased sharply until a plateau was reached, which was caused by the rearrangement of methyl groups. The increasing adsorbed amount of PPO-b-PNIPAm resulted in the rearrangement of isopropyl groups, which changed from a lying down or horizontal conformation to a standing up or vertical conformation. This behavior led to the decrease in surface tension in part III until the critical micelle concentration (CMC) was reached. The surface tension of PPO-b-PNIPAm was thermally responsive. Except for the hysteresis observed in the first cycle, the surface tension was reversible during the heating-and-cooling cycles. At low concentrations, the low surface tension at higher temperatures was mainly caused by the increasing adsorption amount and ordered arrangement of methyl groups, while the standing up conformation of isopropyl groups at higher concentrations resulted in the low surface tension observed at high temperatures.