Enthalpy Relaxation in Poly(4‐hydroxystyrene)/Poly(methyl methacrylate) Blends

Abstract

Abstract Summary: The influence of blend composition on enthalpy relaxation behaviour was assessed for miscible blends of poly(4‐hydroxystyrene)/poly(methyl methacrylate) (PHS/PMMA). Values of enthalpy lost (Δ H ( T a , t a )) were calculated from experimental data plotted against log 10 ( t a ) and modelled using the Cowie‐Ferguson (CF) semi‐empirical model. This gives a set of values for three adjustable parameters, Δ H ∞ ( T a ), log 10 ( t c ) and β . The blends relaxed more slowly than PMMA, but more quickly and less co‐operatively than PHS. Moreover, the blends released more enthalpy than PMMA, but less than PHS. The enthalpy lost by the fully relaxed glass (Δ H ∞ ( T a )) was less than the theoretical amount possible on reaching the state defined by the liquid enthalpy line extrapolated into the glassy region (Δ H max ( T a )). Infrared spectroscopy was used for assessing the hydrogen bonding interactions in the blends. The ageing results are discussed with reference to the hydrogen bonding interactions. Dependence of Δ T (□) and Δ C p (▴) on PHS/PMMA blend composition. magnified image Dependence of Δ T (□) and Δ C p (▴) on PHS/PMMA blend composition.