Surface modification of PVC films in solvent-non-solvent mixtures

Appropriate reaction conditions for the selective surface modification of PVC films with sodium azide and amino thiophenol were investigated. Whilst the use of a phase-transfer agent makes it possible for the nucleolphilic substitution reaction to occur, the morphology of the film is changed by the reaction, leading to a loss in both surface smoothness and transparency of the film. On the other hand, performing the reaction in mixtures of a good and a non-solvent for PVC modification takes place in a controlled manner and the film remains both smooth and transparent. The degree of modification can be varied as a function of time, of temperature and the proportion solvent to nonsolvent used in the reaction. The determination of the overall degree of modification of films of different thickness allows one to draw conclusions about the surface selectivity of the reaction. According to this study, the reaction with sodium azide occurs homogeneously through the film, whilst the use of amino thiophenol leads to a polymer film which is preferentially modified at the surface. (C) 2000 Elsevier Science Ltd. All rights reserved.