Study of the Second Order Transitions and Acid-Base Properties of Polymers Adsorbed on Oxides by Using Inverse Gas...

In Part I, we gave the details concerning inverse gas chromatography (IGC) at infinite dilution and the methods and models that will be used to characterize solid substrates. This technique proved to be an excellent technique to determine not only the glass transitions, but also beta-transition and liquid-liquid transitions of polymers adsorbed on solid substrates. In this second part, we used the IGC technique to determine the second order transitions of the systems' polymethyl methacrylate (PMMA)/SiO(2) and PMMA/Al(2)O(3), at various covered surface fractions and for various tacticities of the polymer. The maxima of the dispersive component of the surface energy gamma(s)(d) of our two systems, obtained by IGC at infinite dilution, indicated clearly the presence of transition temperatures (glass or local transitions). In general, we observed with PMMA three principal maxima that reflect the changes in motions leading to reorganization and rearrangement of the various groups or chain segments of the polymer. The change in the retention mechanism of the probes at the transition temperatures is attributed to an increased molecular mobility of the polymer segments, allowing for the penetration of the probes into the polymer layer. The study of the chemical physical properties of PMMA/SiO(2) and PMMA/Al(2)O(3) revealed an important difference in the acidic and basic behavior, in Lewis terms, of oxide covered by various concentrations of PMMA. This study also highlighted an important effect of the tacticity of the polymer on the acidic basic character of PMMA adsorbed on oxides. Copyright 2001 Academic Press.