Anomalous behaviour of ultrahigh molecular weight poly(methyl methacrylate) in the converging and shear flows

The shear and converging flows of ultrahigh molecular weight poly(methyl methacrylate) (PMMA) solutions is compared with the flow of polystyrene solutions of a similar molecular weight. Two processes occur during the flow of PMMA solution: (i) stereo-complexes that are formed in semi-dilute solutions are reversibly destroyed above a certain stress and/or at elevated temperature and (ii) polymer chains are irreversibly broken in strong shear and converging flows.