Impact of end-group association and main-chain hydration on the thermosensitive properties of hydrophobically modified telechelic poly(N-isopropylacrylamides) in water
Impact of end-group association and main-chain hydration on the thermosensitive properties of hydrophobically modified telechelic poly(N-isopropylacrylamides) in water
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DOI：
10.1021/ma051876z
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发表时间：
2006-01-10
期刊：
影响因子：
5.5
通讯作者：
Winnik, FM
中科院分区：
文献类型：
--
作者：
Kujawa, P;Segui, F;Winnik, FM
我们研究的浊点温度（T-CP）和温度的线圈到球的转变（T-M）在水溶液中的疏水改性（HM）的遥爪聚（N-异丙基丙烯酰胺）（PNIPAM）的浓度范围从0.01到35 g L-1（0.1-310 mmol的NIPAM L-1）的大分子链长度的影响。在S-1-正十八烷基-S ′-（α，α ′-二甲基-α ′-N-n-十八烷基乙酰胺）三硫代碳酸酯作为链转移剂存在下，通过NIPAM在二氧六环中的RAFT聚合得到具有正十八烷基末端的遥爪HM-PNIPAM样品。它们的摩尔质量（M-n）范围为12 000至49 000 g mol（-1），多分散指数低于1.20。通过监测温度引起的散射强度的变化来测量的浊点温度随着聚合物浓度的增加而显着降低，这种效果随着聚合物摩尔质量的降低而更加明显。相比之下，PNIPAM链线圈到球的塌缩的温度（30 +/-1 ° C）仅轻微地受溶液浓度和聚合物分子量的影响。这些结果被解释在共存的两种现象：协会的正十八烷基端基和水合的PNIPAM链。
We examine the influence of the macromolecule chain length on the cloud point temperature (T-cp) and the temperature of the coil-to-globule transition (T-M) in aqueous solutions of hydrophobically modified (HM) telechelic poly(N-isopropylacrylamides) (PNIPAM) ranging in concentration from 0.01 to 35 g L-1 (0.1-310 mmol of NIPAM L-1). The telechelic HM-PNIPAM samples with n-octadecyl termini were obtained by RAFT polymerization of NIPAM in dioxane in the presence of S-1-n-octadecyl-S'-(alpha,alpha'-dimethyl-alpha'-N-n-octadecylacetamide )trithiocarbonate as a chain transfer agent. Their molar mass (M-n) ranged from 12 000 to 49 000 g mol(-1) with a polydispersity index lower than 1.20. The cloud point temperatures, measured by monitoring the temperature-induced changes in scattering intensity, decreased significantly with increasing polymer concentration, this effect being more pronounced with decreasing polymer molar mass. In contrast, the temperature of the PNIPAM chain coil-to-globule collapse (30 +/- 1 degrees C) was only slightly affected by solution concentration and polymer molecular weight. These results are interpreted in terms of the coexistence of two phenomena: association of the n-octadecyl terminal groups and hydration of the PNIPAM chains.