Rietveld IB, Bedeaux D, Smit JA
Colloid and Interface Science Group, LIC, Gorlaeus Laboratories, Leiden University, Leiden, 2300 RA, The Netherlands
J Colloid Interface Sci. 2000 Dec 15;232(2):317-325. doi: 10.1006/jcis.2000.7187.
The inverse osmotic compressibility of the poly(propylene imine) dendrimers in deuterated methanol has been measured as a function of concentration with small-angle neutron scattering. The experimental results reveal three different regimes. First, there is a dilute regime going up to a maximum in the inverse osmotic compressibility. This region can be subdivided into a very dilute region, where the behavior is hard-sphere-like, and a denser region, where the solvation layers overlap. The maximum, occurring around volume fraction 0.30 for each generation, is found to be the concentration where the distance between the centers of two dendrimers is twice their radius of gyration. It designates the crossover to the second regime of a semidilute phase with shrinking dendrimers. Interpenetration of the dendrimers does not seem to take place. Finally, for the higher generations, at high concentrations, the dendrimers are collapsed and the inverse osmotic compressibility starts to increase again. As dendrimers are regularly and very highly branched molecules, they can be considered as ultimately hyperbranched polymers. For both types, the experimental inverse osmotic compressibility shows similar features. The dendrimers seem to be more compact, however. Copyright 2000 Academic Press.
利用小角中子散射测量了聚（丙烯亚胺）树枝状大分子在氘代甲醇中的反渗透压缩性随浓度的变化。实验结果揭示了三种不同的状态。首先，存在一个稀溶液状态，其反渗透压缩性上升至最大值。该区域可细分为行为类似硬球的极稀区域和溶剂化层重叠的较浓区域。每一代在体积分数约为0.30处出现的最大值，被发现是两个树枝状大分子中心之间的距离为其回转半径两倍时的浓度。它标志着向树枝状大分子收缩的半稀相第二状态的转变。树枝状大分子之间似乎没有发生相互贯穿。最后，对于更高代数的树枝状大分子，在高浓度下，它们会塌陷，反渗透压缩性又开始增加。由于树枝状大分子是规则且高度分支的分子，它们可被视为最终的超支化聚合物。对于这两种类型，实验测得的反渗透压缩性表现出相似的特征。然而，树枝状大分子似乎更紧凑。版权所有2000年学术出版社。
