SUMMARY:Thermomechanical degradation of polystyrene (PS) at 180" and 250°C resulted in main chain scission and a small decrease in the molecular weight, as measured by inherent viscosity. The lower molecular weight was retained in the presence of maleic anhydride (MAH) although the latter was incorporated into the PS. The presence of benzoyl peroxide and dicumyl peroxide in the molten PS resulted in a significant molecular weight reduction, due to disproportionation of the internal radicals generated by hydrogen atom abstraction from the PS backbone. The extent of peroxide-induced degradation was greatly reduced in the presence of MAH which presumably added to the internal PS radicals before their disproportionation. The low MAH content of the reaction product despite the use of high concentrations of MAH and peroxides is attributed to the quenching of MAH excimers by PS. ZUSAMMENFASSUNG:Der

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Pyrene‐labeled functionalized ethylene‐propylene (EP) copolymer was prepared by grafting 1‐pyrenebutyrylhydrazine onto EP copolymer through maleic anhydride pendants. The EP copolymer contained 60 mol % ethylene; its weight‐average molecular weight (Mw) was 148,000. The pyrene‐labeled amide functionalized EP copolymer, PA‐EP(60/40), was made to simulate the amine functionalized EP copolymers that are commonly used as dispersant additives in motor oils. UV absorption spectra, fluorescence emission and excitation spectra, and fluorescence decay profiles of the pyrene were studied to determine the copolymer conformation and dynamics in methylcyclohexane and tetrahydrofuran (THF). The pyrene fluorescence characteristics of PA‐EP(60/40) were highly dependent on the solvent. The dependence of fluorescence emission intensity on the excitation wavelength was large in methylcyclohexane and moderate in THF. A frequency shift of about 2 nm was observed between the excitation spectrum obtained with the emission line at 377 nm and that at 550 nm in the methylcyclohexane solutions, but no shift was found in the corresponding tetrahydrofuran solutions. The ratios of the preexponential factors (a21/a22) of the excimer decays obtained in both methylcyclohexane and THF solutions were different from −1.0. However, the deviation of the excimer formation process from the Birks scheme is small in THF but large in methylcyclohexane. In addition, the Huggins constants obtained from intrinsic viscosity measurements of the PA‐EP(60/40) copolymer solutions suggest that copolymer aggregation occurs in methylcyclohexane but not in THF. H‐bonding between two pyrene‐containing pendants is apparently the main driving force for the formation of the ground state pyrene complex. THF is found to be effective in inhibiting the H‐bonding formation. © 1995 John Wiley & Sons, Inc.

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