Simulations of polymer solutions displaying a lower critical solution temperature

Sammanfattning: Thermoresponsive polymers with a lower critical solution temperature, LCST, have attracted interest in the development of new ``smart materials'', which change properties in response to external stimuli. Polymers with an LCST near physiological temperatures are especially relevant in biomedical applications, most notably perhaps in drug delivery systems. The aim of this work is to investigate polymer solutions with an LCST using a coarse-grained model where the monomers of the polymer chains exist in one of two states; one solvophilic and one solvophobic state, where the degeneracy of the solvophobic state is higher than that of the solvophilic. Metropolis Monte Carlo simulations were performed on both single-chain and multiple-chain systems, and on chain lengths varying between 20 and 400 monomers. Simulations on single-chain systems showed a collapse for chains with 40 or more monomers, while the investigated multiple-chain systems of all chain lengths aggregated. Due to fluctuations in the temperature at which the collapse occurred, as well as inconsistencies between simulations performed by decreasing and increasing the temperature, further investigations are needed to determine the limitations of the model and its usefulness in describing polymer solution behaviour.