Effect of Urea on Phase Transition of Poly(N-isopropylacrylamide) and Poly(N,N-diethylacrylamide) Hydrogels: A Clue for Urea-Induced Denaturation
Effect of Urea on Phase Transition of Poly(N-isopropylacrylamide) and Poly(N,N-diethylacrylamide) Hydrogels: A Clue for Urea-Induced Denaturation
复制标题
DOI：
10.1021/acs.macromol.5b01949
复制
发表时间：
2016-01
期刊：
影响因子：
5.5
通讯作者：
Jian Wang;Biaolan Liu;Geying Ru;Jianguo Bai;Jiwen Feng
中科院分区：
文献类型：
--
作者：
Jian Wang;Biaolan Liu;Geying Ru;Jianguo Bai;Jiwen Feng
1H MAS NMR 光谱已用于研究尿素对两种类似热敏聚合物水凝胶的相变影响：聚（N-异丙基丙烯酰胺）（PNIPAM）和聚（N,N-二乙基丙烯酰胺）（PDEA）。研究发现，尿素以相反的方式影响水凝胶的相变：降低PNIPAM的下临界溶液温度（LCST），从而稳定其球状结构，而提高PDEA的LCST，使球状结构不稳定。自扩散系数和尿素聚合物核欧沃豪塞效应（NOE）测量表明，尿素与 PNIPAM 的相互作用强于与 PDEA 的相互作用。此外，增强的水-PNIPAM NOE 表明尿素不仅通过氢键直接与 PNIPAM 相互作用，而且还增强了水和 PNIPAM 之间的氢键相互作用。我们认为，由于酰胺氢的存在或不存在而导致的不同脲-聚合物氢键相互作用与不同的 LCST 变化相关。
1H MAS NMR spectroscopy has been applied to study the urea effect on phase transition of two similar thermosensitive polymer hydrogels: poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-diethylacrylamide) (PDEA). It is found that urea influences the phase transition of the hydrogels in opposite ways: lowering the lower critical solution temperature (LCST) of PNIPAM and hence stabilizing its globular structure, whereas raising the LCST of PDEA and destabilizing the globular structure. The self-diffusion coefficient and urea–polymer nuclear Overhauser effect (NOE) measurement reveal that urea has a stronger interaction with PNIPAM than with PDEA. Moreover, the enhanced positive water–PNIPAM NOE suggests that urea not only interacts directly with PNIPAM via hydrogen bond but also intensifies the hydrogen bonding interaction between water and PNIPAM. We suggest that different urea–polymer hydrogen bonding interaction due to the presence or absence of amide hydrogen is correlated with the distinct LCST variati...