Formation of EDA Complexes in Polymer Mixtures

Abstract

Heterogeneous mixtures of elastomers and plastomers are of practical importance and have been widely investigated. As a result of a small difference in solubility parameter values a diffusion boundary between components of a mixture or an interfacial chemical bonding between polymers are formed. It is commonly accepted that good mechanical properties of such a systems in the two mentioned cases are observed. It is also evident that mixing conditions and a morphology of a mixture play an important role. In this work it was rather unexpectedly stated that the presence of polyacrylonitrile in blends causes strong increase of viscosity and tensile strength of unsaturated elastomers. Those effects are clearly related to double bonds content in elastomer. A lowered segmental mobility of a matrix in the vicinity of plastomer domains was observed by means of mechanical spectrometry and pulsed NMR methods. It is concluded that the charge transfer mechanism between cyano groups of polyacrylonitrile and double bonds is probably responsible for that phenomenon. This hypothesis was confirmed on the basis of IR and UV spectroscopy examinations of model substances: dodecene-1 and butyronitrile. The constitution of the complex was established and the enthalpy of its formation calculated.