Stereospecificity in the adsorption of tactic PMMA on silica

The mechanisms of the adsorption of stereoregular polymers are only poorly understood. This work is devoted to the study of the influence of PMMA tact icity and conformation on the interfacial behavior of the polymer. H-1 NMR usually used to determine the tacticity of PMMA in solution in CDCl3 can al so be applied to systems containing the adsorbed polymer. The strong relati ve lowering of the peak ascribed to isotactic sequences has provided eviden ce of a stereospecific adsorption of the isotactic segments. These isotacti c segments of i-PMMA show the most significant preference for the adsorptio n, while the isotactic sequences of the a- and s-PMMA also show this prefer ence. The selective adsorption is more pronounced at room temperature than above the conformational transition temperature, namely, 50 degrees C. The conformation induced by the PMMA stereoregularity may, therefore, he consid ered as a significant factor in the adsorption process. The driving forces assumed to induce the stereoselective adsorption are discussed.