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首页> 外文期刊>Journal of Colloid and Interface Science >COIL-TO-GLOBULE TYPE TRANSITIONS AND SWELLING OF POLY(N-ISOPROPYLACRYLAMIDE) AND POLY(ACRYLAMIDE) AT LATEX INTERFACES IN ALCOHOL-WATER MIXTURES
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COIL-TO-GLOBULE TYPE TRANSITIONS AND SWELLING OF POLY(N-ISOPROPYLACRYLAMIDE) AND POLY(ACRYLAMIDE) AT LATEX INTERFACES IN ALCOHOL-WATER MIXTURES

机译：醇-水混合物在乳胶界面上的气-球型转变和聚（N-异丙烯酰亚酰胺）和聚（丙烯酰胺）溶胀

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The coil-to-globule type transition and swelling of poly(N-isopropylacrylamide) chains at latex interfaces in mixed dispersion media were studied. A combined collapse-swelling behavior was observed on the addition of lower alcohols (methanol, ethanol, or 2-propanol) to an aqueous dispersion medium. The PNIPAM chains collapsed to a minimum size in the water-rich region and then reswelled on further addition of the alcohol. Both collapse and reswelling were reversible. The collapse of the higher molecular weight PNIPAM chains with narrower polydispersity was found to proceed almost to completion and to be relatively sharp prior to the attainment of theta conditions. It was found that the minimum size of the collapsed chains was dependent upon both the number of carbon atoms in the alcohol and the temperature studied. The volume fraction of alcohol corresponding to this minimum size was also dependent upon the number of carbon atoms in the alcohol but was essentially independent of the temperature of the dispersion medium. The experimental observations have been explained by the variations in the hydrophobic interactions and the hydration of the polymer chains. The results suggest that the collapse of interfacial PNIPAM chains in the alcohol-water mixed media occurs as a consequence of the effects of alcohols on the environment of the PNIPAM chains, whereas the chain swelling results from the direct interaction of the alcohol molecules with the hydrophobic groups in the PNIPAM macromolecules. The attractive hydrophobic interactions in PNIPAM layers are believed to play an important role in promoting the chain collapse after the interactions between the PNIPAM chains and the alcohols are diminished. The validity of this interpretation was supported by similar studies on poly(acrylamide). (C) 1996 Academic Press, Inc. [References: 51]
机译：研究了混合分散介质中胶乳界面处聚（N-异丙基丙烯酰胺）链的盘绕-球型转变和溶胀。在向水性分散介质中添加低级醇（甲醇，乙醇或2-丙醇）后，观察到了合并的塌陷-溶胀行为。 PNIPAM链在富水区塌陷至最小尺寸，然后在进一步添加醇后溶胀。崩溃和再膨胀都是可逆的。发现具有较窄的多分散性的较高分子量的PNIPAM链的崩溃几乎完全完成，并且在达到θ条件之前比较尖锐。发现塌缩链的最小尺寸取决于醇中碳原子数和所研究的温度。对应于该最小尺寸的醇的体积分数还取决于醇中的碳原子数，但基本上与分散介质的温度无关。实验观察已通过疏水性相互作用和聚合物链的水合变化来解释。结果表明，醇-水混合介质中界面PNIPAM链的崩溃是由于醇对PNIPAM链环境的影响而发生的，而链膨胀是由醇分子与疏水性分子的直接相互作用造成的PNIPAM大分子中的基团。在PNIPAM链和醇之间的相互作用被减少之后，PNIPAM层中的有吸引力的疏水相互作用被认为在促进链塌陷中起重要作用。这种解释的有效性得到了对聚丙烯酰胺的类似研究的支持。 （C）1996 Academic Press，Inc. [参考：51]

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