Proprietes des polymethacrylates de methyle branche et lineaire en solutions bi- et tridimensionnelles

Abstract

Branched and linear polyvinyl acetates have already been studied in bi- and tridimensional solutions and there was agreement between the properties of the two types of solution. These polymers were characterized by their flexibility. In the present paper, the influence of branching is studied in the case of a more rigid macromolecule (polymethyl methacrylate) to determine the part due to the cohesion of the polymer. The measurements were performed particularly in bidimensional solution (air-water interface) where the substrate has the properties of a poor solvent so allowing greater differentiation between branched and linear polymers of the same molecular weight. In bidimensional solution, the dependence of surface pressure upon the temperature of the substrate, at low surface concentrations, allows determination of the surface second virial coefficients, the spreading entropies and enthalpies, and demonstrates a smaller interaction between the branched polymer and the substrate. The interfacial study is completed with measurement of surface pressure and viscoelasticity (creep and stress relaxation phenomena) of condensed monolayers. The results show that the branched polymer has a more organized structure than the linear.