Microcalorimetric study of the temperature-induced phase separation in aqueous solutions of poly(2-isopropyl-2-oxazolines)
Microcalorimetric study of the temperature-induced phase separation in aqueous solutions of poly(2-isopropyl-2-oxazolines)
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DOI：
10.1021/ma0358733
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发表时间：
2004-04-06
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：
Diab, C;Akiyama, Y;Winnik, FM
温度对分子量为1900 ~ 5700 g mol（-1）的聚（2-异丙基-2-恶唑啉）（PIPOZ）样品水溶液的影响通过浊度法、高灵敏度微量热法（HS DSC）和压力扰动量热法（PPC）在10 ~ 80 ℃进行监测。该聚合物可溶于冷水，并根据其分子量在类似于45-63 ℃的T-CP下进行相分离。相变是吸热的，焓变范围为0.36 +/- 0.01至1.16 +/- 0.01 kcal mol（-1）。通过PPC测定的PIPOZ在水中的热膨胀系数（α（pol））在对应于相变开始的温度下经历急剧增加，在类似于T-CP的T下达到最大值。用PIPOZ样品在D2 O和NaCl水溶液中的溶液进行微量热测量。与PIPOZ水溶液的相变相关联的热力学和体积变化与两种相关聚合物的水溶液的那些相比较，聚（乙烯基己内酰胺）和聚（N-异丙基丙烯酰胺）（PNIPAM），在结构上与PIPOZ相关的聚合物在水中在类似于31 ℃下经历相变。
The effect of temperature on aqueous solutions of poly(2-isopropyl-2-oxazoline) (PIPOZ) samples of molecular weights ranging from 1900 to 5700 g mol(-1) was monitored by turbidimetry, high-sensitivity microcalorimetry (HS DSC), and pressure perturbation calorimetry (PPC) from 10 to 80 degreesC. The polymers were soluble in cold water and underwent phase separation at T-CP similar to 45-63 degreesC, depending on their molecular weight. The phase transition was endothermic, with an enthalpy change ranging from 0.36 +/- 0.01 to 1.16 +/- 0.01 kcal mol(-1). The coefficient of thermal expansion of PIPOZ in water (alpha(pol)), determined by PPC, underwent a sharp increase at the temperature corresponding to the onset of phase transition, reaching a maximum value at T similar to T-CP. Microcalorimetric measurements were carried out with solutions of PIPOZ samples in D2O and in aqueous NaCl solutions. The thermodynamic and volumetric changes associated with the phase transition of aqueous PIPOZ solutions are compared to those of aqueous solutions of two related polymers, poly(vinylcaprolactam) and poly(N-isopropylacrylamide) (PNIPAM), a polymer structurally related to PIPOZ that undergoes a phase transition in water at similar to31 degreesC.