聚N-异丙基丙烯酰胺共聚物的动态光散射研究

Study on dynamic light scattering of poly(N-isopropylacrylamide) copolymer

以双键类单体N-异丙基丙烯酰胺(NIPAAm)、甲基丙烯酸(3-三甲氧基硅)丙酯(MPS)和甲基丙烯酸羟丙酯(HPMA)为原料,通过自由基聚合法制备了温敏性PNMH共聚物。利用动态光散射仪测试了共聚物在不同水溶液中的水力学直径,考查了温度、pH及盐类溶质对共聚物尺寸、构型及其最低临界溶液温度(LCST)的影响,同时分析了分子内/间作用力的影响规律。结果表明:合成的PNMH共聚物的LCST约为29℃。温敏性共聚物的尺度和构型及其LCST受到水合氢键、非水合氢键和疏水相互作用的综合影响,即水合氢键保持单分子链的尺寸和形态,非水合氢键和疏水相互作用导致分子内卷曲和分子间团聚,静电斥力削弱共聚物的团聚程度。

The thermosensitive poly(N-isopropylacrylamide)(PNMH) copolymers were synthesized by free radical polymerization bearing N-isopropylacrylamide(NIPAAm),3-trimethoxysilypropyl methacrylate(MPS) and hydroxypropyl methacrylate(HPMA).The hydrodynamic diameters of the copolymers in various aqueous solutions were determined by dynamic light scattering.The effects of temperature, pH value and saline solute on the size, conformation and lower critical solution temperature(LCST) of the copolymers were studied, and further analyzed the intramolecular/intermolecular forces.The measurements revealed the LCST of PNMH copolymers of approximately 29℃.The results demonstrated that the scale and configuration of the thermosensitive copolymers and their LCSTs were influenced by the combined effects of hydrated hydrogen bonding, non-hydrated hydrogen bonding and hydrophobic interaction.The hydrated hydrogen bonds keep the size and structure of single molecular chain.The non-hydrated hydrogen bonds and hydrophobic interaction caused intramolecular collapse and intermolecular aggregation.The electrostatic repulsion reduced the agglomeration degree of the copolymers.