Molecular simulation and mathematical modelling of glass transition temperature depression induced by CO₂ plasticization in Polysulfone membranes

A sequence of molecular modelling procedure has been proposed to simulate experimentally validated membrane structure characterizing the effect of CO₂ plasticization, whereby it can be subsequently employed to elucidate the depression in glass transition temperature ( T_g ). Based on the above motivation, unswollen and swollen Polysulfone membrane structures with different CO₂ loadings have been constructed, whereby the accuracy has been validated through good compliance with experimentally measured physical properties. It is found that the presence of CO₂ constitutes to enhancement in polymeric chain relaxation, which consequently promotes the enlargement of molecular spacing and causes dilation in the membrane matrix. A series of glass transition temperature treatment has been conducted on the verified molecular structure to elucidate the effect of CO₂ loadings to the depression in T_g induced by plasticization. Subsequently, a modified Michealis-Menten (M-M) function has been implemented to quantify the effect of CO₂ loading attributed to plasticization towards T_g . (paper)