Selective absorption uptake during the guest-exchange process in the delta form of syndiotactic polystyrene (sPS) was confirmed by IR spectroscopy. When films of the delta form were immersed in hexane/decane or chloroform/decane mixtures, decane molecules were incorporated preferentially in the delta form. Sorbate uptake by the delta form was greatly accelerated when the sorbate was mixed with a solvent penetrable to the amorphous region of sPS.