Truzzolillo D, Bordi F, Cametti C, Sennato S
Dipartimento di Fisica, Universita' di Roma La Sapienza, Piazzale A. Moro 5, I-00185 Rome, Italy.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Jan;79(1 Pt 1):011804. doi: 10.1103/PhysRevE.79.011804. Epub 2009 Jan 16.
The low-frequency limit of the electrical conductivity (dc conductivity) of differently flexible polyions in aqueous solutions has been measured over an extended polyion concentration range, covering both the dilute and semidilute (entangled and unentangled) regime, up to the concentrated regime. The data have been analyzed taking into account the different flexibility of the polymer chains according to the scaling theory of polyion solutions, in the case of flexible polyions, and according to the Manning model, in the case of rigid polyions. In both cases, the fraction f of free counterions, released into the aqueous phase from the ionizable polyion groups, has been evaluated and its dependence on the polyion concentration determined. Our results show that the counterion condensation follows at least three different regimes in dependence on the polyion concentration. The fraction f of free counterions remains constant only in the semidilute regime (a region that we have named the Manning regime), while there is a marked dependence on the polyion concentration both in the dilute and in the concentrated regime. These results are briefly discussed in the light of the scaling theory of polyelectrolyte aqueous solutions.
在较宽的聚离子浓度范围内，对不同柔性的聚离子在水溶液中的电导率低频极限（直流电导率）进行了测量，该浓度范围涵盖稀溶液和半稀溶液（缠结和未缠结）状态，直至浓溶液状态。对于柔性聚离子，根据聚离子溶液的标度理论，对于刚性聚离子，根据曼宁模型，在考虑聚合物链不同柔性的情况下对数据进行了分析。在这两种情况下，均评估了从可电离聚离子基团释放到水相中的自由抗衡离子分数f，并确定了其对聚离子浓度的依赖性。我们的结果表明，抗衡离子凝聚至少遵循三种不同的状态，这取决于聚离子浓度。自由抗衡离子分数f仅在半稀溶液状态（我们命名为曼宁状态的区域）保持恒定，而在稀溶液和浓溶液状态下，其对聚离子浓度均有显著依赖性。根据聚电解质水溶液的标度理论，对这些结果进行了简要讨论。
