Rietveld Ivo B., Bedeaux Dick
Colloid and Interface Science Group, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, Leiden, 2300 RA, The Netherlands
J Colloid Interface Sci. 2001 Mar 1;235(1):89-92. doi: 10.1006/jcis.2000.7250.
The viscosity of solutions of poly(propylene imine) dendrimers in methanol has been determined. An Ubbelohde and a low-shear rotational viscometer have been used. The viscosity was Newtonian for every concentration and shear rate used. The value of the Huggins coefficient indicates soft sphere behavior. The viscosity of the lower generations as a function of the volume fraction can be described with a single exponent, where the exponent is comparable to the intrinsic viscosity. The viscosity of the 4th and 5th generation dendrimers shows a stronger increase from a volume fraction of about 0.15 to 0.30. This increase is much smaller than that expected, using the Krieger-Dougherty formula for hard spheres with the hydrodynamic radius determined from the intrinsic viscosity. This smaller increase and the small value of the Huggins coefficient are interpreted in terms of a breakdown of the solvation layer. At a volume fraction of 0.3 the dendrimers, using the radius of gyration as the radius, start to touch each other. From the dependence of the viscosity on the concentration and the dependence of the viscosity on the molar weight, it can be concluded that dendrimers do not interpenetrate. It is concluded that they deform (collapse). Copyright 2001 Academic Press.
已测定了聚（丙烯亚胺）树枝状大分子在甲醇中的溶液粘度。使用了乌氏粘度计和低剪切旋转粘度计。在所使用的每种浓度和剪切速率下，粘度均为牛顿型。哈金斯系数的值表明其具有软球行为。较低代数树枝状大分子的粘度作为体积分数的函数可用单一指数来描述，其中该指数与特性粘度相当。第四代和第五代树枝状大分子的粘度从约0.15的体积分数增加到0.30时呈现出更强的增长。与使用根据特性粘度确定的流体力学半径的硬球的克里格 - 多尔蒂公式所预期的相比，这种增长要小得多。这种较小的增长以及哈金斯系数的较小值是根据溶剂化层的破坏来解释的。在0.3的体积分数下，以回转半径作为半径，树枝状大分子开始相互接触。从粘度对浓度的依赖性以及粘度对分子量的依赖性可以得出结论，树枝状大分子不会相互渗透。得出的结论是它们会变形（塌陷）。版权所有2001年学术出版社。
