State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
J Chem Phys. 2011 Jan 21;134(3):034903. doi: 10.1063/1.3532090.
Telechelic polyelectrolytes, bearing short hydrophobic blocks at both ends, will ionize into polyions and their counterions when dissolved in water. With the variation of concentration, the interplay between short range attraction and the long range electrostatic interaction as well as the counterion distribution exerts a major influence on the chain conformations (two basic conformations: loop and nonloop, the latter can be subdivided into three association types: free, dangling, and bridge), the cluster structure and the forming of a physical gel. For weak hydrophobic interaction, the relative strong electrostatic interaction dominates the gelation progress; sol-gel transition occurs at higher concentrations due to electrostatic screening and mainly involves the forming of stretched nonloop conformations such as dangling and bridge. While for strong hydrophobic interaction, the hydrophobic interaction dominates and the electrostatic interaction provides a contribution to the formation of gels by maintaining a spatial swelling structure, resulting in a much lower concentration region of sol-gel transition; besides, the sol-gel transition is characterized by the competition of the forming of loop and bridge chains.
两亲性末端带有短疏水链的遥爪聚合物在水中离解为聚离子及其抗衡离子。在浓度变化时，短程吸引力和长程静电相互作用以及抗衡离子分布之间的相互作用对链构象（两种基本构象：环和非环，后者可细分为三种缔合类型：自由、悬垂和桥联）、簇结构和形成物理凝胶有重要影响。对于弱疏水相互作用，相对较强的静电相互作用主导着凝胶化过程；由于静电屏蔽，较高浓度下发生溶胶-凝胶转变，主要涉及悬垂和桥联等伸展的非环构象的形成。而对于强疏水相互作用，疏水相互作用占主导地位，静电相互作用通过维持空间溶胀结构对凝胶的形成做出贡献，导致溶胶-凝胶转变的浓度区域大大降低；此外，溶胶-凝胶转变的特点是环和桥链的形成竞争。
