Theoretical investigation of charge effects on the critical solution temperature of thermosensitive, random copolymers

功能化的温敏聚合物已经成为开发具有可调性能的智能、环境敏感材料的不可或缺的组成部分。尤其是在接近较低的临界溶液温度(LCST或浊点)时，共聚物的材料性质仅因溶剂环境的微小变化而发生显著变化。本项目从理论上研究了静电荷电和盐的特殊筛选对基于聚乙二醇酯(PEG)、聚N-异丙基丙烯酰胺(PNIPAM)和带电聚丙烯酸的热敏性无规(带电)共聚物的LCST的影响。这将使用原子和粗粒计算机模拟、统计力学工具和最近提出的在非均质聚合物表面上的离子分配的概念相结合来执行。这个项目的主要目标是：首先，也是最重要的，合理的电荷组成/结构和盐筛选对共聚物的结构、热力学和LCST的影响。其次，在微观模拟的基础上，了解特定盐之间在改变带电共聚物的LCST的潜力方面的强烈多样性。第三，验证分配概念的可转移性，从而建立一个理论框架来定量描述和预测给定共聚物组成和盐的LCST变化。该项目的结果将有助于描述和提出实验共聚序列的特定设计基序，从而产生所需的环境敏感响应。

Functionalized, thermosensitive polymers have become an integral building block for the development of smart, environment-sensitive materials with tunable properties. In particular close to their lower critical solution temperature (LCST or cloud point) copolymers show dramatic changes in their material properties in response to only tiny changes in the solvent environment. This project theoretically investigates the effects of electrostatic charging and specific screening by salts on the LCST of thermosensitive, random (and charged) copolymers based on polyethylene glycole (PEG), Poly(N-isopropylacrylamide) (PNIPAM), and electrostatically charged poly(acrylic)acid. This will be performed using a combination of atomistic and coarse-grained computer simulations, tools of statistical mechanics, and the recently proposed concept of ion partitioning at heterogeneous polymer surfaces. The key objectives of this project are: firstly and most importantly, to rationalize the influence of charge composition/architecture and salt screening on the structure, thermodynamics, and LCST of the copolymers. Secondly, to understand the strong diversity among specific salts in their potential to alter the LCST of charged copolymers based on microscopic simulation insights. Thirdly, to validate the transferability of the partitioning concept and thereby develop a theoretical framework to quantitatively describe and predict changes in LCST for a given copolymer composition and salt. The results of this project will help to describe and propose specific design motifs for experimental copolymeric sequences leading to a desired environment-sensitive response.