title: Volume phase transition of polyelectrolyte gels: effects of ionic size.
abstract: Although the volume transition of the polyelectrolyte gel has been studied for decades, less study on the finite size effects of the mobile ions has been conducted. In the present paper, Tanaka's classical theory of polyelectrolyte gel is extended to the cases of mobile ions of finite volume. In the salt free limit, the theoretical results show that the discontinuous volume transition of the polyelectrolyte gel will become a continuous one for counterionic size larger than a critical value. When a significant amount of salt is added, the critical value for the volume transition increases as a result of electrostatic screening. An increase in salt concentration can also make the polyelectrolyte gel in poor solvent collapse. Poorer solvent is needed to trigger the salt-induced collapse in polyelectrolyte gel with larger mobile ions than that with smaller ones. The effects of ionic size on the critical points and phase diagram of the volume transition are also discussed. The theoretical results suggest that the swelling behavior of polyelectrolyte gel might be tuned with salt of different volumes.
authors.affiliation: Department of Physics, Beijing Normal University, Beijing 100875, China.
authors.forename: Li-Jian
authors.initials: LJ
authors.lastname: Qu
authors.affiliation: School of Science, Beijing Jiaotong University, Beijing 100044, China.
authors.forename: Xinghua
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Jiuzhou
authors.initials: J
authors.lastname: Tang
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Physics, Beijing Normal University, Beijing 100875, China.
authors.forename: Dadong
authors.initials: D
authors.lastname: Yan