Reactions in polymer blends:: Experiment and theory -: (A review)

Results of experimental and theoretical investigations of reactions in polymer blends which have been performed in the last decade are surveyed. Experimenters extensively study relatively simple model systems: homogeneous and quasi-homogeneous melts or bilayer and trilayer films with well-defined interfaces. These studies make it possible to evaluate the contributions of reactivity and diffusion to the reaction kinetics, to reveal the specific features of reactions at the interface, to establish the mechanism of influence of block copolymers on the structure stabilization in incompatible blends, etc. The following achievements in theory are noted. The structure evolution of a blend of compatible (reacting and accelerating) polymers by the concerted action of a polymer-analogous reaction involving intra- and interchain acceleration effects and interdiffusion was first described by the methods of linear nonequilibrium thermodynamics. The effect of a diblock copolymer on both the equilibrium of a dispersed blend of incompatible polymers and the dynamics of the system was described: the particle growth via the Ostwald ripening mechanism, and competition between the spinodal decomposition of a quasi-homogeneous blend and the in situ formation reaction of the diblock copolymer. The evolution of the molecular-mass distribution and block-length distribution of the products of interchain exchange in a homogeneous system was studied analytically and by Monte Carlo simulation. Some unsolved problems in this area are discussed.