报告题目：Origin of the Entropic Driving Force in Polyelectrolyte Complex Coacervation

报 告 人：王振纲（美国工程院院士、加州理工学院讲座教授）

报告时间：2025年6月12日下午13:30

报告地点：五山科技园2号楼324报告厅

邀请人：周嘉嘉教授

主办单位：前沿软物质学院 

报告摘要：

　　Mixing two solutions of oppositely charged polyelectrolytes under appropriate conditions results in a liquid–liquid phase separation into a polymer-rich coacervate phase and a coexisting polymer-poor supernatant phase. This polyelectrolyte complex coacervation (PCC) has received considerable attention in recent years due to its relevance to membraneless organelles in biology, and applications in biomedical and biomimetic systems. The complexation of oppositely charged polymers has been widely believed to be driven by the entropy gain due to counterion release. In this talk, we show that a large portion of the entropy change is due to solvent (water) reorganization, which we can extract by exploiting the temperature dependence of the dielectric constant.  For weakly-to-moderately charged systems under common conditions (monovalent ions, room temperature in aqueous solvent), the solvent reorganization entropy, rather than the counterion release entropy, is the primary entropy contribution. We use this framework to examine the two elementary stages in the symmetric PCC—the complexation between a polycation and polyanion, and the subsequent condensation of the polycation–polyanion pairs by computing the potential of mean-force (PMF) using molecular dynamics simulation. From the calculated PMF, we find that the supernatant phase consists predominantly of polyion pairs with vanishingly small concentration of bare polyelectrolytes, and we provide an estimate of the spinodal of the supernatant phase. Finally, we show that prior to contact, two neutral polyion pairs weakly attract each other by mutually induced polarization, providing the initial driving force for the fusion of the pairs. 

个人简介：

　　王振纲教授 1982 年毕业于北京大学化学系。1987 年获芝加哥大学博士。之后分别在 Exxon公司和加州大学洛杉矶分校做博士后研究。1991年受聘于美国加州理工学院化学与化工学部，现为美国加州理工学院 Dick and Barbara Dickinson 讲座教授。

　　王振纲教授是国际知名的高分子和软物质理论物理学家。主要研究领域涉及高分子溶液、混合物和共聚物的热力学与动力学；表面和界面；液晶态、胶体和凝胶；软物质体系的静电相互作用；DNA 和 RNA的生物物理和病毒自组装；生物膜物理等。2001 年当选美国物理学会会士。2008 年获美国加州理工学院最高教学奖Richard P. Feynman 奖。2025年当选美国工程院院士。