Sorption and desorption of carbon dioxide (CO2) in polycarbonate (PC) with different dimensions were systematically investigated at temperatures of 40, 60, and 80 degrees C; pressures ranged from 7 to 20 MPa; and soaking time ranged from 0.5 to 4 h. The experimental data were analyzed by a mass-loss analysis. With the assumption of Fickian diffusion, the sorption amount and the sorption diffusivities (D-s) under supercritical conditions, and desorption diffusivities (D-d) under ambient temperature and pressure were determined. The crossover of the sorption isotherms was presented, which indicated that the change of mass transfer mechanism had occurred. It was found that D-s increased with temperature, whereas D-d showed a contrary trend. Moreover, the linear relationship between sorption amount and specific surface area was also observed, which suggested that the specific surface area was one of the important factors on the sorption amount for thick samples in swelling process. (C) 2008 Wiley Periodicals, Inc.