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

功能化的热敏聚合物已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。特别是在接近其较低临界溶液温度（LCST或云点）时，共聚物的材料性能仅对溶剂环境的微小变化做出反应。本项目从理论上研究了静电充电和盐的特定筛选对热敏、随机（带电）共聚物(基于聚乙二醇（PEG）、聚（n -异丙基丙烯酰胺）（PNIPAM）和静电充电聚（丙烯酸）酸的LCST的影响。这将使用原子和粗粒度计算机模拟、统计力学工具以及最近提出的非均质聚合物表面离子分配概念的组合来执行。该项目的主要目标是：首先，也是最重要的是，理顺电荷组成/结构和盐筛选对共聚物结构、热力学和LCST的影响。其次，根据微观模拟的见解，了解特定盐在改变带电共聚物的LCST方面的潜力。第三，验证分配概念的可转移性，从而建立一个理论框架，以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，从而获得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.