混合溶剂中聚甲基丙烯酸甲酯稀溶液粘度行为研究

利用毛细管管径为0．38mm的乌式粘度计测定了25℃时聚甲基丙烯酸甲酯PMMA在丁酮／环己烷混合溶剂中的粘度，发现在高分子溶液流过时间t测定之前和之后纯溶剂在粘度计流过时间t0和t0′并不一致．利用(t/t0-1)/C计算比浓粘度ηsp/C,则溶液被稀释时ηsp／C在低浓度时出现正偏离；利用(t/t0′-1)/C计算比浓粘度ηsp/C，则即便在低浓度区溶液被稀释时ηsp/C和C之间依旧满足线性关系．根据本文提出的实验方法，t0和t0′之间的差异可以被用来定量确定高分子吸附层厚度，结果表明高分子吸附层厚度和高分子在溶液中的构象密切相关．

Studies on the Viscosity of PMMA in Mixed Solvents at Lower Concentrations

The viscosity of poly (methyl methacrylate) (PMMA) in a solvent mixture of butanone/cyclohexane with different volume ratios at 25 ℃ was measured using an Ubbelohde viscometer with a capillary diameter of 0.38mm. It was found that t0 and t'0, corresponding to the flow time of the pure solvent measured respectively before and after the flow time of polymer solution t was recorded, were not the same. The reduced viscosity ηsp/C determined by (t/t0 - 1 )/C exhibited a drastic increase with dilution, similar to the experimental results obtained by Ohrn. On the other hand, ηsp/C determined by ( t/t'0 - 1 )/ C was proportional to C even at low concentrations. The difference between t0 and t'0, as presented in this paper, could be used to determine the thickness of the adsorbed polymer layers on the capillary walls quantitatively. It was noted that the thickness of the adsorbed polymer layers was strongly related to the configuration of the polymer molecules in solution.