Molecular orientation of EVA chains adsorbed on chemically controlled surfaces: influence of specific interactions

Abstract

AbstractMolecular orientation of ethylene–vinyl acetate (EVA) copolymer nanofilms adsorbed on chemically controlled surfaces is studied. Four EVA copolymers with different contents of vinyl acetate (VA) were spin‐coated onto gold, COOH and NH2 functionalized substrates in order to study chain behaviour when adsorbed in a quasi‐two‐dimensional system. Polarization‐modulation infrared reflection–absorption spectroscopy (PM‐IRRAS), a very suitable technique to study thin films, was the key to quantitative calculation of EVA chain orientational angles. Acid–base interactions between carbonyl groups of the chain ramification (vinyl acetate units) and the surface functionalities are evidenced on the basis of infrared spectra. Their incidence on the molecular orientation is also discussed.Our results show a quasi‐parallel orientation of EVA main chains with respect to the surface plane for all adsorption substrates. At the same time, orientation changes of the acetate groups are observed when the EVA copolymer is adsorbed onto functionalized substrates, suggesting that acid–base interactions could influence the orientation of these groups. However, these changes are limited and cannot reorient the main chain axis. Moreover, our results show that increasing VA content in the chain does not lead to more carbonyl functions involved in acid–base interactions with the adsorption surface. This fact also will be discussed. Copyright © 2003 John Wiley & Sons, Ltd.