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Deuterated polybutadiene and protonated polybutadiene (PBD/PBH) blends with various microstructures have been studied by the small-angle neutron scattering experiments. Correlation length, £, zero wavenumber structure factor, S(q = 0), and interaction parameter, xblend, have been obtained. All PBD/PBH blends exhibit UCST behavior. With the use of random copolymer theory, the interaction parameter, xblend, has been successfully separated into xlf 2, and 3 which are interaction parameters between the same isotopically labeled 1,2-unit and 1,4-unit, the opposite isotopically labeled 1,2-unit and 1,4-unit, and the opposite isotopically labeled 1,2-unit and 1,2-unit or 1,4-unit and 1,4-unit, respectively.

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The morphology of solution cast films of butadiene and styrene block polymers in both stretched and unstretched state has been studied by electron microscopy, and has been related to the mechanical behavior of these materials. These micrographs confirm the indications from dynamic properties that this material consists of a two‐phase system in which the relationship between the phases is sensitive to the solvent system used in casting. Although the basic morphological unit is a polystyrene sphere of 100 Å diameter dispersed in a matrix of polybutadiene, the interaction between spheres is complex. These spheres are more deformable than would be predicted from their glass transition temperature. The dynamic mechanical properties, stress‐strain properties, and stress relaxation properties of block polymers of styrene and dienes can be explained in terms of the morphology and changes of morphology on stretching in the electron microscope.