A study of thermoassociative gelation of aqueous cationic poly(N-isopropyl acrylamide) graft copolymer solutions
A study of thermoassociative gelation of aqueous cationic poly(N-isopropyl acrylamide) graft copolymer solutions
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DOI：
10.1016/j.polymer.2009.01.035
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发表时间：
2009-03-06
期刊：
影响因子：
4.6
通讯作者：
Saunders, B. R.
中科院分区：
文献类型：
--
作者：
Liu, R.;Cellesi, F.;Saunders, B. R.
在这项工作中，热缔合凝胶形成的一个新的家庭的水温度响应性共聚物溶液进行了研究。这使用最近制备的阳离子聚（N-异丙基丙烯酰胺）（PNIPAm）接枝共聚物来实现[Liu R，De Leonardis P，Cellesi F，Tirelli N，Saunders BR. Langmuir 2008：24：7099]。PDMA（+）（x）-g-（PNIPAmn）（y）共聚物具有源自大分子引发剂的x和y值; n的值对应于PNIPAm臂长。DMA（+）是季铵化的甲基丙烯酸N，N-二甲基氨基乙酯。共聚物溶液表现出约33 ℃的浊点温度（T-clpt），其不受x/y比或n值的显著影响。在大于或等于4 wt.%的共聚物浓度（C-copol）下，在T-clpt以上发生热缔合凝胶形成。这是相当低的C-copol值，并且是所采用的接枝共聚物结构的结果。采用变温动态流变学方法研究了温度、共聚单体及共聚物结构对凝胶化和凝胶弹性的影响。对于39 ℃下的PDMA（30）（+）-g-（PNIPAm 210）（14）溶液，发现G'（弹性模量）与C-copol成比例，根据类似于C-copol（3.85）的G'。数据表明，PNIPAm单元的很大一部分不直接参与网络形成。这些系统的热缔合凝胶形成和凝胶性质似乎受涉及DMA（+）单元的静电排斥（有利于共聚物主链的空间延伸）和PNIPAm侧链之间有吸引力的疏水相互作用（有利于缔合交联形成）之间的平衡支配。(C)2009爱思唯尔有限公司保留所有权利。
In this work thermoassociative gel formation of a new family of aqueous temperature-responsive copolymer solutions has been investigated. This was achieved using a cationic poly(N-isopropyl acrylamide) (PNIPAm) graft copolymer recently prepared [Liu R, De Leonardis P, Cellesi F, Tirelli N, Saunders BR. Langmuir 2008:24:7099]. The PDMA(+) (x)-g-(PNIPAmn)(y) copolymers have x and y values that originate from the macroinitiator; the value for n corresponds to the PNIPAm arm length. DMA(+) is quarternarized N,N-dimethylaminoethyl methacrylate. The copolymer solutions exhibited cloud point temperatures (T-clpt) of about 33 degrees C, which were not significantly affected by x/y ratio or the value for n. Thermoassociative gel formation occurred above T-clpt at copolymer concentrations (C-copol) greater than or equal to 4 wt.%. This is a reasonably low C-copol value and is a consequence of the graft copolymer architecture employed. We investigated the effect of temperature, C-copol and copolymer structure on gelation and gel elasticity using variable - temperature dynamic rheology. For PDMA(30)(+)-g-(PNIPAm210)(14) solutions at 39 degrees C it was found that G' (elastic modulus) scales with C-copol according to G' similar to C-copol(3.85). The data suggested that a significant proportion of PNIPAm units is not directly involved in network formation. Thermoassociative gel formation and the gel properties for these systems appear to be governed by a balance between electrostatic repulsion involving the DMA(+) units (favouring spatial extension of the copolymer backbones) and attractive hydrophobic interactions between PNIPAm side chains (favouring associative crosslink formation). (C) 2009 Elsevier Ltd. All rights reserved.