Adsorption Isotope Effect for Protio- and Deuteropolystyrene at a Single Solid Surface

Infrared spectroscopy was employed, in the mode of attenuated total reflection (ATR), to measure PS adsorption to the native surface of a silicon infrared prism. Infrared spectra were collected, and the silicon ATR prism was prepared using methods described previously. The temperature of measurement was 30.0°C, which is the Θ temperature, T_θ, for deuteropolystyrene (PS-d) in cyclohexane.⁶ For protiopolystyrene (PS-h) in cyclohexane, T_θ = 34.5°C,⁶, so that PS-d at 30°C finds itself in a slightly better solvent than does PS-h. Calibrations showed that Beer's law held to a good approximation for these films of low adsorbance as expected,⁷ and that the PS free in solution (0.2 mg·mL^-1) contributed only approximately 1% to the measured PS absorption peaks. At this solution concentration, PS-d and PS-h are completely miscible.