Size effects on miscibility and glass transition temperature of binary polymer blend films

After determining the size dependent miscibility of binary polymer blend films using molecular dynamics simulation and thermodynamics, the size dependent glass transition temperatures Tg(w,D) of several polymer blend films in miscible ranges are determined by computer simulation and the Fox equation where w is the weight fraction of the second component and D denotes thickness of films. The Tg(w,D) function of a thin film can decrease or increase as D decreases depending on their surface or interface states. The computer simulation results are consistent with available experimental results and theoretical results for polymer blend films of PPO/PS poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene] and stereoregular PMMA/PEO poly(methyl methacrylate)/poly(ethylene oxide)]. The physical background of the above results is related to the root of mean square displacement of thin films in their different regions.