Inverse thermally-reversible gelation of aqueous N-isopropylacrylamide copolymer solutions
Inverse thermally-reversible gelation of aqueous N-isopropylacrylamide copolymer solutions
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DOI：
10.1016/s0032-3861(97)00612-5
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发表时间：
1998-06-01
期刊：
影响因子：
4.6
通讯作者：
Bae, YH
中科院分区：
文献类型：
--
作者：
Han, CK;Bae, YH
在苯中合成了一批聚n -异丙基丙烯酰胺-共丙烯酸（n -异丙基丙烯酰胺-共丙烯酸）。共聚物是具有各种较长临界溶液温度的聚合物的共混物。超过临界浓度的共聚物水溶液在加热时经历四个不同的相。其中一个相是凝胶相，在凝胶-溶胶过渡中表现出可逆性，没有明显的滞后或协同作用。凝胶一旦形成，在温度达到另一个转变点之前，它不会溶解或改变含水量。这个特殊的过程与分子量、链缠结、分子在高温下从膨胀的线圈到部分聚合物的崩溃小球的转变以及随后崩溃的小球聚集形成弱物理连接有关。这些连接可以从目前已知的胶凝过程中的物理交联中区分出来。坍塌的聚合物链的热诱导分子聚集可能是导致凝胶不透明、凝胶诱导时间可忽略不计、缺乏迟滞和非弹性变形的原因。1998爱思唯尔科学有限公司版权所有。
A batch of poly(N-isopropylacrylamide-co-acrylic acid) synthesized in benzene shows distributions in molecular weight as well as polymer composition. The copolymer turns out to be a blend of polymers having various lon er critical solution temperatures. An aqueous solution of the copolymer above a critical concentration experiences four distinct phases upon heating. One of the phases is a gel phase that shows reversibility in gel-sol transition without noticeable hysteresis or syneresis. Once the gel is formed, it does not dissolve or change in water content until the temperature reaches another transition point. This particular process is related to the molecular weight, the chain entanglement, the molecular transition at elevated temperatures from expanded coils to collapsed globules of a portion of the polymers, and the subsequent aggregation of the collapsed globules to make weak physical junctions. The junctions can be discriminated from the physical cross-linking involved in gelation processes known so far. The thermally induced molecular aggregation of the collapsed polymer chains may be responsible for the gel opacity, negligible gel induction time, lack of hysteresis, and non-elastic deformation. (C) 1998 Elsevier Science Ltd. All rights reserved.