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

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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.