An ATR-IR Study of Poly (Dimethylsiloxane) under High-Pressure Carbon Dioxide: Simultaneous Measurement of Sorption and Swelling

摘要

The CO_2 sorption and the consequent swelling of un-cross-linked poly (dimethylsiloxane) (PDMS) have been measured simultaneously at high pressure using in-situ ATR (Attenuated Total Reflectance)-IR spectroscopy. The absorbance of the v_3 (2335 cm~(-1)) band of CO_2 dissolved in PDMS was used to determine quantitative sorption data. The absorbance of the IR band of PDMS was used to calculated the polymer swelling. Data at 25 ℃ and 50 ℃ for pressures up to 12 MPa are reported and compared to literature values. A shift of the δ(CH_3) band of PDMS (at 1259 cm~(-1)) was observed with the increase of sorbed CO_2 and was related to the swelling of the polymer. This is a novel use for high-pressure in-situ ATR-IR spectroscopy, which allows the simultaneous measurement of gas sorption and polymer swelling and provides molecular-level insight into the behavior of polymers under high-pressure or supercritical CO_2.