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组成部分。特别是在接近它们的较低临界溶解温度（LCST或浊点）时，共聚物显示出它们的材料性质的显著变化，仅响应于溶剂环境中的微小变化。本项目从理论上研究了静电荷和盐的特定屏蔽对基于聚乙二醇（PEG）、聚（N-异丙基丙烯酰胺）（PNIPAM）和静电荷聚（丙烯酸）的热敏性无规（和带电）共聚物的LCST的影响。这将使用原子和粗粒度的计算机模拟，统计力学的工具，以及最近提出的概念，在异质聚合物表面的离子分区的组合。该项目的主要目标是：首先，最重要的是，合理化的电荷组成/架构和盐筛选的共聚物的结构，热力学和LCST的影响。第二，基于微观模拟的见解，了解特定盐在改变带电共聚物的LCST方面的潜在差异。第三，验证分配概念的可转移性，从而开发一个理论框架来定量描述和预测给定共聚物组合物和盐的LCST的变化。这个项目的结果将有助于描述和提出具体的设计图案的实验共聚序列导致所需的环境敏感的响应。

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.