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

✍ Scribed by Iain M. G. Cowie; Valeria Arrighi; Elizabeth-Anne McGonigle

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 184 KB
• Volume: 206
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200400485

✦ Synopsis

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 imageDependence of Δ__T__ (□) and Δ__C__~p~ (▴) on PHS/PMMA blend composition.