Polystyrene networks were synthesized by free radical polymerization of styrene in the presence of dibenzoyl peroxide as an initiator, divinylbenzene as a crosslinker at 50 °C in toluene under nitrogen atmosphere. The swelling behavior of the synthesized polystyrene networks were studied at different temperatures in methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, tert-butyl acetate, and isopentyl acetate. Equations were given for the variation of the polymer-solvent interaction parameter, χ12, as a function of reciprocal absolute temperature in the temperature range from 25 to 75 °C. Polystyrene networks were swollen in linear polystyrene solutions in toluene of different concentrations. Linear polystyrene samples were almost monodisperse and of high molecular weight. The equilibrium swelling degrees were evaluated using the Flory-Rehner theory. The relation of volume swelling ratio, q
, to the volume fraction of the linear polymer in solution, φ, was evaluated and characterized by interaction parameter of crosslinked polystyrene with linear polystyrene, χ23. The parameter χ23 was found around zero as expected from mixtures of similar chemical structures by extrapolating the values of χ23 at tested concentrations to zero solvent concentration.