Shew Chwen-Yang, Yoshikawa Kenichi
Department of Chemistry, College of Staten Island and Graduate Center, City University of New York, Staten Island, New York 10314, USA.
J Chem Phys. 2007 Apr 14;126(14):144913. doi: 10.1063/1.2714552.
The diMarzio theory has been extended to elucidate the intermolecular and intramolecular phase segregations of a single flexible chain polyelectrolyte in dilute salt-free solutions. At the long chain limit, this theory yields the formalism obtained from the more sophisticated Edward Hamiltonian for polyelectrolyte problems. The calculated phase diagram exhibits the features of a first-order phase transition, with continuous and discontinuous transitions separated by a critical point. Under the discontinuous transition, the polyelectrolyte chain exhibits coexistent expanded and collapsed conformational states, same as intermolecular phase segregation. For a limiting long chain, the mean chain size at critical point is roughly 90% of the size of an ideal chain. Such a result implies that partial contraction within a chain molecule is required to collapse a flexible polyelectrolyte chain. Moreover, the theory predicts that for a longer chain, intramolecular segregated conformations differ significantly from intermolecular segregated conformations, but the difference becomes small for shorter chains. Besides, the charge needed to induce intramolecular segregation is smaller than that of intermolecular segregation for a given chain length. These findings are consistent with previous literature results.
迪马尔齐奥理论已得到扩展，以阐明稀无盐溶液中单一柔性链聚电解质的分子间和分子内相分离。在长链极限情况下，该理论得出了从更复杂的爱德华哈密顿量用于聚电解质问题所获得的形式体系。计算得到的相图呈现出一级相变的特征，连续和不连续相变由一个临界点分隔。在不连续相变下，聚电解质链呈现出共存的伸展和塌缩构象状态，这与分子间相分离相同。对于极限长链，临界点处的平均链尺寸约为理想链尺寸的90%。这样的结果意味着，要使柔性聚电解质链塌缩，链分子内需要部分收缩。此外，该理论预测，对于较长的链，分子内分离构象与分子间分离构象有显著差异，但对于较短的链，这种差异会变小。此外，对于给定的链长，诱导分子内分离所需的电荷比分子间分离所需的电荷小。这些发现与先前的文献结果一致。
