Coil-to-globule transition of thermo-responsive gamma-substituted poly (epsilon-caprolactone) in water: A molecular dynamics simulation study

A Koochaki and MR Moghbeli and SJ Nikkhah, CURRENT APPLIED PHYSICS, 18, 1313-1319 (2018).

DOI: 10.1016/j.cap.2018.07.011

The coil-to-globule behavior of polygamma-2-2-(2methoxyethoxy)ethoxyethoxy-3-caprolactonel (PMEEECL) as a gamma-substituted poly (epsilon-caprolactone) was investigated via atomistic molecular dynamics (MD) simulation. For this purpose, radius of gyration, end-to-end distance and radial distribution function of the chain in the presence of water were calculated. Consequently, the lower critical solution temperature (LCST) of PMEEECL chain at which the coil- to-globule transition takes place, was determined in each calculated parameter curve. The simulation results indicated that the LCST of PMEEECL was occurred at close to 320 K, which is in a good agreement with previous experimental results. Additionally, the appearance of sudden change in both Flory-Huggins interaction parameter (chi) and interaction energy between the PMEEECL chain and water molecules at about 320 K confirmed the calculated LCST result. The radial distribution function (RDF) results showed that the affinity of the PMEEECL side chain to water molecules is lower than its backbone.