During the copolymerization of styrene with divinylbenzene

a series of samples were taken at different gelation time from the beginning to the end of this reaction.For sol samples before and after gelation point time Tg(=18.15h)

the weight average molecular weight (Mw)

the mean square radius of gyration (Rg) of the polymer chain in solution

the second virial coefficient (A2)

hydrodynamic radius (Rh)

parameter δ(=Rg/Rh) and the size distribution for these samples were determined by static light scattering and dynamic light scattering.Before Tg

both Mw and Rg increase rapidly

then become divergence near Tg and reach the maximum at Tg.Rh almost follows the same way except not so rapidly.After Tg all go down.A2 decrease gradually following the gelation.δ are 2.78

3.80 and 1.87 at 15h

18.25h and 29h

respectively

which agree with the rules of linear and branching polystyrene.The size distribution of these sol samples always were rather wide and before Tg and after Tg

their diameters tend to increase and decrease

respectively.Based on these data

the evolution rules of these parameters were withdrawn and the quantitative characterization of span process of gelation was carried out successfully.