Polymer excluded volume exponent v : An experimental verification of the n vector model for n = 0

Three light scattering experiments (Y. Miyaki et al., Macromolecules 11 (1978) 1180 ; M. Fukuda et al., J. Polym. Sci. 12 (1974) 871; A. Yamamoto et al., Polymer J. 2 (1971) 799) for polystyrene benzene dilute solutions are analysed. These very careful measurements give the variations of the radius of gyration < R 2 >1/2 and of the second virial coefficient A 2 as a function of the molecular weight (0.246 x 106 ≤ Mw ≤ 56 × 106). These data are corrected here for polydispersity effects and analysed in order to determine the excluded volume exponent v. The obtained value : v = 0.586 ± 0.004 from < R2 > is in better agreement with the critical theory (v = 0.588) than with the theory of Flory (v = 0.60). This result is confirmed by the A2 data.