1H MAS NMR studies of the phase separation of poly(N-isopropylacrylamide) gel in binary solvents.
1H MAS NMR studies of the phase separation of poly(N-isopropylacrylamide) gel in binary solvents.
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DOI：
10.1021/la8038363
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发表时间：
2009-05
期刊：
影响因子：
--
通讯作者：
Nian Wang;Geying Ru;Liying Wang;Jiwen Feng
中科院分区：
文献类型：
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作者：
Nian Wang;Geying Ru;Liying Wang;Jiwen Feng
采用变温高分辨率1H MAS NMR研究了二元水/醇（水/甲醇和水/乙醇）混合物中溶剂与聚n -异丙基丙烯酰胺（PNIPAM）凝胶网络的优先相互作用。PNIPAM凝胶在二元溶剂中的核磁共振结果显示，在LCST上方存在两种不同类型的水/醇混合物：束缚在凝胶内部的二元溶剂，以及从凝胶中排出的自由二元溶剂。有趣的是，密闭溶液中的酒精浓度明显高于自由溶液中的酒精浓度。此外，在这两种醇中，乙醇在受限溶液中的浓度更高。这些结果表明，聚合物优先与醇分子而不是水分子相互作用，并且具有较高疏水性的醇在PNIPAM上表现出更高的优先吸收。我们的结果还表明，对两种不同类型的溶液进行的1H NMR测量为表征溶剂在聚合物上的优先吸附提供了一种方便、直接的方法。
Preferential interactions of solvents with poly(N-isopropylacrylamide) (PNIPAM) gel networks in binary water/alcohol (water/methanol and water/ethanol) mixtures have been investigated using variable-temperature high-resolution 1H MAS NMR. NMR results for PNIPAM gel in the binary solvents reveal the existence of two distinct types of water/alcohol mixtures above the LCST: confined binary solvents bound inside the gel, and free binary solvents expelled from the gel. It is interesting to find that the alcohol concentration in confined solution is significantly higher than that in free solution. Moreover, of the two alcohols, ethanol is more significantly concentrated in the confined solution. These results demonstrate that the polymer preferentially interacts with alcohol molecules over water and that the alcohol with higher hydrophobicity exhibits higher preferential absorption on PNIPAM. Our results also show that 1H NMR measurements made on two distinct types of solution provide a convenient, direct means of characterizing the preferential adsorption of solvent on polymer.