Glass Transition Temperature and Isothermal Physical Aging of PMMA Thin Films Incorporated with POSS

Abstract

Thin (similar to 650 nm) and ultrathin (similar to 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 PUSS 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 (Delta H-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 Delta H-Relax vs. aging time data providing the fitting parameters; maximum enthalpy recovery (Delta H-infinity), relaxation time (tau) and non-exponentiality parameter (beta).