Kawata Yuuki, Kozuka Shohei, Yusa Shin-Ichi
Department of Applied Chemistry , University of Hyogo , 2167 Shosha , Himeji , Hyogo 671-2280 , Japan.
Langmuir. 2019 Feb 5;35(5):1458-1464. doi: 10.1021/acs.langmuir.8b01684. Epub 2018 Aug 21.
Amphoteric diblock copolymers (SA ) composed of poly(2-acrylamido-2-methylpropanesulfonic acid sodium salt) (PAMPS) with poly(3-(acrylamido)propyl trimethylammonium chloride) (PAPTAC) blocks were synthesized via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. Three SA were prepared with a fixed degree of polymerization (DP) for the PAMPS block (= 82) and different DP values for the PAPTAC blocks ( n = 37, 83, and 183). The solubility of SA was studied at different sodium chloride (NaCl) concentrations. SA precipitated in pure water due to attractive electrostatic interactions with interpolymer chains. Conversely, SA and SA dissolved in pure water. In pure water SA dissolved as a unimer state due to electrostatic repulsion of excess anionic charges in the polymer chain. The long anionic PAMPS block segment in SA covered the short cationic PAPTAC block segment within a single polymer chain. In pure water SA dispersed as polyion complex micelles due to electrostatic repulsion of the cationic PAPTAC shells. The oppositely charged PAMPS and PAPTAC blocks in SA formed a core, while the excess PAPTAC block formed shells. SA showed lower critical solution temperature (LCST)-type thermo-responsive behavior at certain NaCl concentrations, and the LCST increased with the NaCl concentration. The mechanism of LCST behavior involves hydrogen bonding interactions between the pendant amide groups and water molecules.
通过可逆加成-断裂链转移（RAFT）自由基聚合反应合成了由聚（2-丙烯酰胺基-2-甲基丙磺酸钠盐）（PAMPS）和聚（3-（丙烯酰胺基）丙基三甲基氯化铵）（PAPTAC）嵌段组成的两性二嵌段共聚物（SA ）。制备了三种SA ，其中PAMPS嵌段的聚合度（DP）固定（= 82），PAPTAC嵌段的DP值不同（n = 37、83和183）。研究了SA 在不同氯化钠（NaCl）浓度下的溶解性。SA 在纯水中沉淀，这是由于与聚合物链间存在吸引性静电相互作用。相反，SA 和SA 可溶于纯水。在纯水中，SA 以单分子状态溶解，这是因为聚合物链中过量阴离子电荷的静电排斥作用。SA 中长的阴离子PAMPS嵌段部分覆盖了单个聚合物链内短的阳离子PAPTAC嵌段部分。在纯水中，SA 由于阳离子PAPTAC壳层的静电排斥作用而分散为聚离子复合胶束。SA 中带相反电荷的PAMPS和PAPTAC嵌段形成一个核，而过量的PAPTAC嵌段形成壳层。SA 在一定NaCl浓度下表现出较低临界溶液温度（LCST）型的热响应行为，且LCST随NaCl浓度增加而升高。LCST行为的机制涉及侧链酰胺基团与水分子之间的氢键相互作用。
