Determination of the transition phenomena of poly(α-n-alkyl) methacrylates adsorbed on silica by inverse gas chromatography (IGC)

Abstract

Inverse gas chromatography (IGC) at infinite dilution is a powerful technique to characterise the superficial and interfacial properties of solid substrates as oxides, polymers or polymers adsorbed on oxides and to determine the transition phenomena of polymers. This technique was applied in earlier studies in order to determine the change, as related to temperature, of the properties and the second order transitions of some polymers adsorbed on oxides, and particularly to study the transition phenomena in PMMA and poly(α-n-propyl) methacrylate (P3) adsorbed on silica or in their bulk phases. In this paper, the superficial properties and glass transitions of poly(α-n-pentyl) methacrylate (P5) and poly(α-n-octyl) methacrylate (P8) were studied when adsorbed on silica or in their bulk phases. The study of the evolution of RTlnVn, as a function of 1/T for different n-alkanes adsorbed on poly(α-n-alkyl) methacrylates (Pn), proved that IGC technique allowed a fairly accurate determination of their transition temperature (Tg). Moreover, the glass transition temperature Tg was observed to vary from 110 °C for PMMA (P1) to 10 °C for poly(α-n-octyl) methacrylate. Results obtained in this study proved an important shift in the value of Tg, due to the adsorption of various Pn on silica and the more spread chains of the adsorbed polymers. A reduction in Tg value was observed when the length of the side chain increases that leads to an internal plastification effect in poly(α-n-alkyl)methacrylates.