Light‐scattering study of polyacrylonitrile solution

Light‐scattering measurements of polyacrylonitrile (PAN) prepared by aqueous suspension polymerization and solution polymerization were made in both dimethylformamide (DMF) and γ‐butyrolactone (γ‐BL). The following relations between the intrinsic viscosity [η] (in deciliters per gram) and the weight‐average molecular weight were obtained: [η] = 3.35 × 10−4 M̄w0.72 (in DMF at 30°C.) and [η] = 4.00 × 10−4 M̄w0.69 (in γ‐BL at 30°C.). The relation in DMF is in agreement with the results of many other researchers, but differs from the results of Bisschops et al. and Peebles. Analysis of the results by the recent viscosity theory reported by Inagaki et al. indicates that the steric factor σ is 2.17 on PAN in both DMF and γ‐BL. It is found that the root‐mean‐square radius of gyration of the chain measured by light scattering 〈S2〉w1/2 (LS) is in good agreement with the root‐mean‐square radius of gyration of the chain calculated by using the viscosity theory of Inagaki et al. 〈S2〉w1/2 (vis) in both DMF and γ‐BL. Relations between the root‐mean‐square radius of gyration of the chain (in Angstroms) in DMF and γ‐BL and the molecular weight were obtained: 〈S2〉w1/2 = 7.94 × 10−2 M̄w0.66 (in DMF) and 〈S2〉w1/2 = 2.19 × 10−1 M̄w0.57 (in γ‐BL). From the estimation of the second virial coefficient A2 and the value of B obtained from viscosity theory, it is found that DMF is a better solvent than γ‐BL.