Small-angle neutron scattering studies of chain conformation in semicrystalline hydrogenated polybutadiene

Mixtures of model crystallizable copolymers, hydrogenated polybutadiene (HPB) and deuterated polybutadiene (DPB), were investigated by SANS in the intermediate q range (0.02 ≤ q ≤ 0.18 Å⁻¹). Linear and three-arm-star polymers were crystallized by quenching and slow cooling at rates differing by 3000-fold. Care was taken in subtracting the incoherent background scattering. The coherent cross section shows a q⁻² dependence which results in a constant Kratky plateau. Absolute SANS intensity is slightly greater than predicted for amorphous chains and is very insensitive to crystallization conditions in these polymers, changing by less than 10%. These observations are interpreted in terms of the gambler's-ruin model for chain configurations in semicrystalline polymers.