Bordi F, Cametti C, Gili T, Sennato S, Zuzzi S, Dou S, Colby R H
Dipartimento di Fisica, Universita' di Roma "La Sapienza," Piazzale A. Moro 5, I-00185 Rome, Italy.
J Chem Phys. 2005 Jun 15;122(23):234906. doi: 10.1063/1.1931607.
We present a set of low-frequency electrical conductivity measurements of solutions of differently charged, salt-free polyelectrolytes in poor- and in good-solvent conditions, in the semidilute concentration regime. The data have been analyzed and discussed in light of the necklace model for hydrophobic polyelectrolytes recently proposed by Dobrynin et al. [Macromolecules 29, 2974 (1996)] that predicts the chains to collapse into spheroidal cores connected by narrow strings. By varying the quality of the solvent, we have measured the polyion equivalent conductance lambda(p) in an extended concentration range in the semidilute regime and have demonstrated that this parameter is influenced by the polyion chain conformation, giving further support, when the poor-solvent condition prevails, to the picture of a string of electrostatic blobs. On the contrary, in good-solvent condition, the electrical conductivity data are in reasonable good agreement with the picture of an extended chain consisting of a collection of electrostatic blobs. These electrical conductivity measurements, in light of scaling theory, furnish new experimental support for the necklace model for hydrophobic polyions in poor solvents.
我们展示了在半稀浓度范围内，不同电荷的无盐聚电解质溶液在不良溶剂和良溶剂条件下的一组低频电导率测量结果。根据多布林宁等人最近提出的疏水聚电解质项链模型[《大分子》29, 2974 (1996)]对数据进行了分析和讨论，该模型预测链会坍缩成由细链连接的球状核。通过改变溶剂的性质，我们在半稀区域的扩展浓度范围内测量了聚离子当量电导λ(p)，并证明该参数受聚离子链构象的影响，当不良溶剂条件占主导时，进一步支持了一串静电团簇的图景。相反，在良溶剂条件下，电导率数据与由一系列静电团簇组成的伸展链的图景相当吻合。根据标度理论，这些电导率测量为不良溶剂中疏水聚离子的项链模型提供了新的实验支持。
