Glass transition temperature and isothermal physical aging of PMMA thin films incorporated with POSS

Abstract

Thin (-650 nm) and ultrathin (-50 nm) films of neat PMMA and PMMA containing 5 wt% of methacryl-polyhedral oligomeric silsesquioxane were prepared in this work. The effects of film thickness and POSS on glass transition temperature (T g) and isothermal physical aging were investigated by means of differential scanning calorimetry (DSC). T g depression was observed as film thickness was decreased and Ma-POSS molecules were incorporated. Enthalpy relaxation (ΔH Relax) due to the isothermal physical aging was reduced by ultra-thin film thickness and the addition of Ma-POSS. KWW (Kohlrausch-Williams-Watts) equation was used to fit ΔH Relax vs. aging time data providing the fitting parameters; maximum enthalpy recovery (ΔH ∞), relaxation time (τ) and non-exponentiality parameter (ß).