Equilibrium swelling in a non—solvent is a simple experimental method to reveal the cohesional entanglement network structure present in an amorphous polymer in its glassy state．In the present work results of visual observation of the swelling behavior of two PS granules in a series of dioxane／water mixed solvents are presented．On decreasing the water content in the mixed solvent a change of physical state of the PS granules from glassy state(water in dioxane≥40 Vol％)to swollen glassy state(water in dioxane 35 Vol％～30 Vol％)．to swollen rubbery state(water in dioxane 25 Vol％～20 Vol％)and to fluid state(water in dioxane 10 Vol％-5 Vol％)was observed．It corresponds to the change from glassy state to rubbery state and to fluid state on raising temperature of the granules．Base on these observations a mixed solvent of dioxane／water(water 6．8 wt％) was chosen for equilibrium swelling and phase separation equilibrium measurements for a monodisperse PS sample of Mm =1．68×105at 30℃．In this mixed solvent PS granule can only swell but not dissolved．For the phase separation equilibrium the PS granule in the mixed solvent wilts first brought to 130℃(in a sealed tube)to become a homogeneous single phase solution

then phase separation occurred on cooling and phase separation equilibrium at 30℃ was reached in 30 days to give a volume fraction of the polymer in the concentrated phase φ”=0．304．The dilute phase is practically the pure solvent．Monodisperse PS granules quenched from being heated to 120℃ for 30 min to erase thermal history of the sample(Pp=1．0451 g／mL)reached a swelling equilibrium in the mixed solvent in 80 days to give φP”=0．308．This quenched PS granules after being subjected to a sub—Tg annealing at 80℃ for 100 days(Pp=1．0470 g／mL)reached swelling equilibrium in the mixed solvent in 70 daysto give φp”=O．312．From the curve of increasing volume of the swollen phase Vg(t)

in mL/g PS

during the equilibrium swelling process it could be inferred that during sub—Tg annealing the cohesional network structure in the PS glass became more uniform

being closer to the equilibrium state at the annealing temperature

the van der Waals crosslinking density was increased

with tighter inter-chain cohesion resulting in higher density of the glass．If we take the polymer-solvent interaction parameter χ=0．63 obtained from phase separation equilibrium measurement

we obtained the molar mass between crosslinking points ofthe network

Mc=11．6×104 for the quenched sample

and Mc=6．9×104for the annealed sample from Flory theory of network swelling．The experimental results clearly indicate that swelling process and swelling equilibrium measurements in a very poor solvent can offer a rather sensitive way to obtain some idea about the structure details of the cohesional network in polymer glassy state．