New approach to characterise physicochemical properties of solid substrates by inverse gas chromatography at infinite dilution II. Study of the transition temperatures of poly(methyl methacrylate) at various tacticities and of poly(methyl methacrylate) adsorbed on alumina and silica

The determination of the temperature transitions in polymers and more particularly when polymers are adsorbed on oxides is very important in many industrial processes. In this second part, we used inverse gas chromatography (IGC) at infinite dilution to determine the second order transition temperatures of poly(methyl methacrylate) (PMMA) adsorbed (or not) on alumina or on silica. Three types of PMMA were used: atactic (a), syndiotactic (syndio) and isotactic (iso). The IGC technique allowed to obtain the net retention volume V-n and the dispersive component of the surface energy gamma(d) for various theoretical models of molecules, using the results of Part I. By plotting RT In V-n as a function of (1/T) or gamma(d) as a function of the temperature T, we proved the presence of three particular temperatures that correspond respectively to the transition temperature relative to beta-relaxation (T-beta), the glass transition temperature (T-g), and the liquid-liquid transition temperature or order-disorder transition (T-II). Results obtained in this part allowed us to show the effect of the tacticity of PMMA and the recovery fraction of polymer adsorbed on alumina or silica on the transition temperatures. (C) 2002 Elsevier Science B.V. All rights reserved.