BEHAVIOR OF MODIFIED AND UNMODIFIED POLYBUTADIENES IN THE SEMIDILUTE REGIME

The association behaviour of polybutadiene modified with 4-phenyl-1,2, 4-triazoline-3,5-dione was studied in semidilute solution through stat ic (SLS) and dynamic light scattering (DLS). The results were compared with the unmodified polybutadiene, whose behavior in semidilute solut ion was also studied as function of the molecular weight. At higher co ncentrations a small-angle excess scattering in SLS and a slow mode mo tion in DLS were observed both for modified and unmodified polybutadie nes suggesting the presence of large clusters. Increasing the polymer concentration, the mass fraction of the slow motion increases up to va lues near 1, indicating a proximity to the gel point. For polybutadien es with low and medium degrees of modification cluster formation was d etected for concentrations lower than for unmodified polybutadiene. Th e presence of these clusters is due to intermolecular association betw een the polar urazole groups. The behaviour of the reduced osmotic mod ulus for various molecular weights of unmodified polybutadiene allowed the conclusion that its association is due to segment-segment attract ive interactions. (C) 1997 Elsevier Science Ltd.