Revisiting of dimensional scaling of linear chains in dilute solutions

The dimensions of linear polymer chains are scaled to their molar mass (M) as R = kMα with α = 1/2 and 3/5 in a theta and an athermal solvent, respectively. In a good solvent, both k and α are a function of the solvent quality and chain length range. A high-temperature laser light-scattering spectrometer was used to measure the average radius of gyration (〈Rg〉) and hydrodynamic radius (〈Rh〉) of a set of narrowly distributed linear polystyrene chains in decalin over a wide temperature range. k and α in the scaling experimentally varying with T over a chain length range was analyzed. The results reveal that for 〈Rg〉, α = 0.59 − 0.09exp(−τ/0.066) and k = 0.60τ2α−1, reasonably agreeing with the thermal blob theory. For 〈Rh〉, α = 0.59 − 0.09exp(−τ/0.106), but k deviates from the relationship of k ∝ τ2α−1, reflecting that the hydrodynamic interaction and chain draining are not considered in the thermal blob theory.