Phase contrast matching in lamellar structures composed of mixtures of labeled and unlabeled block copolymer for small-angle neutron scattering

To extract the single-chain scattering function of polystyrene block chain in lamellar structures of styrene-2-vinylpyridine diblock copolymers, the method of "phase contrast matching" was studied for small-angle neutron scattering from blends of the deuterium-labeled and unlabeled block copolymers. The phase contrast matching is successfully applied for the samples with the lowest molecular weights (3.4 x 10 exp 4 for the labeled portions) but not for the samples with the higher molecular weights (9.2 and 16.2 x 10 exp 4 ). It is concluded that the mismatching may be caused by concentration fluctuation in the mixture of hydrogenated and deuteriated polystyrenes in domains, and by nonuniform distribution of deuteriated species along the direction perpendicular to the lamellae due to the difference in lengths of the labeled and unlabeled blocks. 24 ref.--AA