Studies with gradient polymers of polystyrene and poly(methyl acrylate)

A series of [net-polystyrene]-ipn-[net-poly(methyl acrylate)] systems with gradients of poly(methyl acrylate) in a polystyrene matrix are prepared and tested mechanically. The results showed no distinct differences from that of corresponding interpenetrating polymer network (IPN) samples with simila r compositions, in contrast to the substantially improved fracture strains obtained for [net-poly(methyl methacrylate)]-ipn-[-net poly(methyl acrylate )] gradient systems and their nongradient IPN's in our previous work. Hence , it is concluded that the toughening effect of gradient structure observed is not universally applicable for all gradient systems but it is unique fo r the acrylic system studied. Moduli-temperature responses and dynamic mech anical spectra of gradients and IPN's prepared in the current study are als o presented. (C) 1999 John Wiley & Sons, Inc.