In situ ATR-IR spectroscopy was used to simultaneously measure the sorption and swelling of carbon dioxide at high pressures in a biocompatible acrylate copolymer poly(methylmethacrylate-co-ethylhexylacrylate-co-ethyleneglycoldimethacr ylate), P(MMA-EHA-EGDMA). The v(3) band of CO2 dissolved in the polymer (at 2335 cm(-1)) was used to calculate the sorption data and the polymer swelling was determined by analyzing the changes in the absorbance of the v(C=O) band (at 1730 cm(-1)) of the polymer. Transmission spectroscopy in the near-IR region was also used to study the sorption Of CO2 in the polymer using combinational and overtone bands. The experiments were carried out in a pressure range of 2.0-12.0 MPa and in a temperature range of 27-40 degrees C. The data for CO2 sorption in this polymer obtained by in situ spectroscopic methods have been compared to the data obtained by the gravimetric technique. (c) 2005 Elsevier B.V. All rights reserved.