Expansion Factor of a Part of a Polymer Chain in a Good Solvent Measured by Small-Angle Neutron Scattering

The radii of gyration of deuterium-labeled sections of polystyrenes with narrow molecular weight distributions were determined in a good solvent (carbon disulfide) by small-angle neutron scattering (SANS). The expansion factors of the labeled sections were calculated from the measured radii of gyration using unperturbed dimensions estimated from literature radius of gyration-molecular weight relationships for polystyrenes. The expansion factors of the labeled sections are smaller than those of the whole chains but are larger than that of a whole chain with the same molecular weight as the labeled section. Both results are reasonable in comparison with a Monte Carlo calculation in the literature and also with the perturbation theory.