PMMA ADSORPTION OVER PREVIOUSLY ADSORBED PS STUDIED BY POLARIZED FTIR-ATR

Polarized infrared spectroscopy in attenuated total reflection was use d to investigate the adsorption of PMMA (polymethylmethacrylate) onto PS (polystyrene) that was previously adsorbed onto oxidized silicon fr om dilute solution in carbon tetrachloride at 30 degrees C. The carbon yl group of PMMA forms hydrogen bonds with surface silanol groups, giv ing segment-surface interaction energy of 4 kT as against 1 kT for PS (k is the Boltzmann constant, T the absolute temperature). The formati on of hydrogen-bonding by PMMA was unaffected, in rate or amount, by p readsorbed PS, but a lesser total amount of PMMA adsorbed onto PS, res ulting in a higher average bound fraction. The histogram of the mass a dsorbed, attributable to subpopulations of chains with different bound fractions, was inferred by subtracting infrared spectra acquired at s uccessive times. Whereas this histogram was broad and bimodal for adso rption onto bare surface, it was narrower and unimodal for adsorption onto preadsorbed PS. (C) 1995 John Wiley & Sons, Inc.