The fractionation

viscosity and light-scattering measurements for three types of polystyrene

i.e.

atactic

isotactic and 1:1 mixture of the two

were studied. Noticeable differences in the [η]-M relationship

second virial coefficients A2 and mean square end-to-end distances were found among the three types of polystyrene samples. Conclusions about the solution properties of isotactic polystyrene suggested by Danusso and confirmed by Krigbaum were discussed.