【作者】 关岚；

【导师】 黄定海；

【作者基本信息】 天津大学 ， 材料学， 2010， 博士

【摘要】 不同相对分子质量聚丙烯酸(PAA)/水的混合物中水的热力学性质与本体水有明显的区别。结晶水含量的结果表明了在亲水聚合物水溶液中除了氢键对水的结晶有影响外,不同长度的聚合物分子链对水的结晶起着不同的空间抑制作用,并且这个作用并不是简单的随着相对分子质量单调变化,而是存在一个临界相对分子质量。不同的聚合物分子结构也是影响不同状态水的含量和结晶性质的因素。混合物中不结晶水在无定形相中的含量都是恒定的,不随着总含水量的增加而变化,唯一的例外是PVME水溶液,原因是由于PVME的特别结构造成的。PAA水溶液中的离子可以明显改变结晶键合水的熔点和熔融焓。PAA水溶液中水的热容值表明当混合物处在玻璃态时,键合水比玻璃态水具有更强的运动能力。随着含水量的增加,聚合物与水分子的平均相互作用力是下降的。聚甲基乙烯基醚(PVME)与水形成了络合体。但是这种络合体是不稳定的。PVME的水合过程是一个较缓慢的过程。不同热历史可以改变PVME/水混合体系中的自由水和结晶键合水的比例。结晶键合水的熔点是没有随着含水量明显改变的,只是数量的改变,而自由水的熔点却是明显增加的。由于相互作用不同,自由水和键合水与PVME的结合速度是不同的。在对PVME水溶液热容的考察说明PVME与水的相互作用较弱,并且水的热容没有随着含水量的增加而明显变化。PVME/水溶液中无定形水含量wa与相分离焓之间的关系表明混合物中主要是不结晶水分子与相分离密切有关。不同商用隐形眼镜的NaCl渗透率结果表明自由体积理论拟合普通HEMA的隐形眼镜盐渗透率的实验结果很好。隐形眼镜的NaCl的渗透率随着体系中结晶水的含量,结晶水与非结晶键合水比值的增加而增加,说明结晶水在控制聚合物凝胶中盐的渗透过程中起着主要的作用。提高隐形眼镜中结晶水含量可以提高盐在聚合物凝胶中的渗透率。更多还原

【Abstract】 The thermal behaviors of the poly(acrylic acid)(PAA)/water mixtures with different polymer Mws were different from those of bulk water. It showed that the polymer chains with different lengths can effect geometrically the crystallization of water, besides the interaction between polymers and water molecules through hydrogen bonding. The effect didn’t vary with Mw linearly; there existed a critical Mw. Different chemical structures can also influence the amounts of different states of water and the water crystallization. The content of non-crystalline water in the amorphous phase in the mixtures was constant, regardless of the water content. One exception was poly(vinyl methyl ether)(PVME)/water mixtures, due to its special structure. The ions in the PAA/water mixtures could change the melting point of freezable bound water and melting enthalpy. The heat capacity of water in the PAA/water mixtures showed that the mobility of the bound water was higher than that of the glassy water. With increasing water content, the average interaction between polymer and water decreased. PVME formed association with water; however, the association was not stable. The process that PVME and water hydrated during cooling was slow. The different thermal histories could affect the amount of different states of water. The Tm of the freezable bound water didn’t vary with the water content evidently, while the ones of free water changed. Time for free water and bound water to interact with PVME is different, due to various interactions. The investigation on the Cp of water in the PVME/water mixtures revealed that the the interaction between PVME and water was small and didn’t change with water content. The content of non-freezable water indicated that the non-freezable water is mainly responsible for the phase separation. The permeabilities of different commercial contact lenses showed that the free volume theory provided the best fitting results for the experimental values. NaCl permeability in lenses increased with the content of freezable water and the ratio of freezable water to non-freezable water, showing that the freezable water is mainly responsible for salt diffusion in the polymer hydrogels. The permeability could be increased by increasing the content of freezable water.更多还原