Behaviour 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 static (SLS) and dynamic light scattering (DLS). The results were compared with the unmodified polybutadiene, whose behavior in semidilute solution was also studied as function of the molecular weight. At higher concentrations a small-angle excess scattering in SLS and a slow mode motion in DLS were observed both for modified and unmodified polybutadienes suggesting the presence of large clusters. Increasing the polymer concentration, the mass fraction of the slow motion increases up to values near 1, indicating a proximity to the gel point. For polybutadienes with low and medium degrees of modification cluster formation was detected for concentrations lower than for unmodified polybutadiene. The presence of these clusters is due to intermolecular association between the polar urazole groups. The behaviour of the reduced osmotic modulus for various molecular weights of unmodified polybutadiene allowed the conclusion that its association is due to segment-segment attractive interactions. (C) 1997 Elsevier Science Ltd.