主讲人：王振纲教授

时间：8月28日下午14:00
地点：丽湖校区守信楼一楼报告厅

报告人简介：

王振纲1982年毕业于北京大学化学系，1987年获芝加哥大学化学博士学位。他先后在埃克森研究与工程公司和加州大学洛杉矶分校进行博士后研究。自1991年起，他任教于加州理工学院化学工程系，现为Dick and Barbara Dickinson讲席教授。他还曾担任化学工程系执行长（系主任）。

王振纲的研究领域是聚合物、软材料和生物物理系统的结构、相行为、界面性质和动力学的理论与计算。他目前的研究活动围绕三个主要方向：带电系统，包括聚电解质、掺盐聚合物和双电层；高分子和软物质中的成核或更广义的势垒跨越过程；以及高分子凝胶和缠结高分子的非线性流变学。

王振纲是美国物理学会会士，并获得过多项重要奖项和荣誉，包括Camille Dreyfus教师学者奖（1995年）、Alfred P. Sloan奖（1996年）、美国化学工程师学会(AIChE)的Braskem奖（2018年）、AIChE Alpha Chi Sigma奖（2023年）和美国物理学会高分子物理奖（2024年）。今年（2025年）当选为美国国家工程院院士。此外，他还获得了加州理工学院最高的教学荣誉—Richard P. Feynman教学卓越奖（2008年）。

王振纲曾担任Journal of Theoretical and Computational Chemistry、Macromolecules、ACS Macro Letters、Giant、Acta Physicochimica Sinica和Science in China B (Chemistry)等期刊的编辑顾问委员会成员。他目前担任美国化学会期刊Macromolecules的副主编。

讲座摘要：

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.

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