Bulk properties of multibranched polystyrenes from polystyrene macromonomers: rheological behavior I

Dynamic shear moduli of multibranched polystyrenes were measured as functio ns of frequency and temperature using a parallel-plate rheometer. The multi branched polystyrenes are poly(macromonomer)s of omega-methacryloyloxyethyl polystyrene macromonomers (MA-PSt)s and statistical copolymers of the MA-P St with methyl methacrylate (MMA) monomer. The master curve of the storage dynamic shear modulus G' for the poly(macromonomer)s did nor show the so-ca lled plateau region and the G' gradually decreased from the edge of the gla ss transition region to the terminal zone and the loss modulus G " was alwa ys larger than G'. The plateau region became clear in the copolymers with l ess branch density. These results indicate that the intermolecular chain en tanglement might be strongly restricted in the poly(macromonomer) systems d ue to the multibranched structure of high branch density, which also explai ns the brittle property of the poly(macromonomer) films. (C) 2000 Elsevier Science Ltd. All rights reserved.