Changes of Interfacial Adhesion by the Addition of Reactive Polymers

Abstract

The effect of the structure of reactive polymers on the interfacial adhesion between immiscible Polystyrene (PS)/Poly(methyl methacrylate) (PMMA) and Poly(phenylene oxide) (PPO)/PMMA polymers was investigated. Mono- or di-carboxy terminated PS, Poly(glycidyl methacrylate) (PGMA) and well defined end-functionalized polymers were used as reactive compatibilizers. The amount of copolymer formed by reaction at an interface was estimated by measuring the interfacial fracture toughness using asymmetric fracture tests. In case of PS/PMMA joints, the dicarboxy terminated PS is more effective in obtaining a higher maximum fracture toughness since it provides two stitches to the interface and the loop conformation yielding two stitches for each dicarboxy PS chain is shown to be possible in present case by considering a simple scaling theory on dry brush type end-grafted chains. The chain areal density (Σ), estimated from the measured fracture toughness, is in good agreement with the value obtained with monodisperse deuterated monocarboxy end-functionalized PS and ion beam technique¹ and scales as N⁻¹ as predicted. In the case of joints between PPO and PMMA, it was demonstrated that in order to see any visible change in the interfacial fracture toughness with end-functionalized PS and PMMA it is required that the end-functionalized reactive polymers be allowed enough time to react each other without diffusive mixing with bulk homopolymer. The reaction rate constant for the reaction between the end-functionalized polymers was estimated by assuming a bimolecular reaction at interface and measuring the fracture toughness. The reaction rate constant estimated for the end-functionalized polymer pair is in fairly reasonable agreement with the value reported by others² even though there is experimental difference in obtaining the reaction rate constant.