Chloroform vapor sorption in semicrystalline syndiotactic polystyrene with a nanoporous crystalline form has been investigated by simultaneous gravimetric and calorimetric analysis to gather information on the sorption process and associated heat of sorption. At the investigated pressures of chloroform vapor, the sorption process is dominated by exothermic adsorption of penetrating molecules in the nanocavities of the crystalline phase. The mass uptake kinetics has been compared with the kinetics of evolution of heat of sorption measured simultaneously. The integral heat of sorption evaluated calorimetrically has been compared to the corresponding value calculated by elaborating gravimetric sorption isotherms at several temperatures evaluated independently through gravimetric sorption experiments. (c) 2005 Wiley Periodicals, Inc.