The dynamic mechanical properties are reported for polybutadienes with different vinyl contents, of poly(1,4-butadiene-b-1,2-butadiene) copolymers with various compositions, block molecular weights and overall molecular weights, and of a number of different blends of the homopolymers. The microstructure of the polymers has been obtained by Raman spectroscopy and the molecular weights by gel permeation chromatography. The morphology of the diblock copolymers, as perceived using dynamic mechanical thermal analytical methods, has been found to be a function of the molecular weight of the individual blocks and the overall molecular weight of the copolymers. The extent of phase separation in the polymer blends is greater than that seen in the diblock copolymers. The glass transition temperature has been shown to be a function of vinyl content in homo-polybutadienes. Comparisons have been drawn between the dynamic mechanical properties of the diblock copolymers and those of polymer blends which have a similar overall microstructural composition.