Modeling of vapor sorption in polymeric film studied by surface plasmon resonance spectroscopy

Sorption process by surface plasmon resonance (SPR) was studied by exposing polymeric film made from anthracene labeled poly(methyl methacrylate) (An-PMMA) chains to various concentrations of saturated chloroform vapor. It was observed that the reflectivity changes were fast and reversible. The changes in reflectivity implied the swelling behavior of polymeric film during adsorbtion and can be explained by capturing of chloroform molecules. When clean air is introduced into gas cell similar behavior is observed but this time in the opposite direction as a result of desorption. Fick's law for diffusion was used to quantify real time SPR data for the swelling and desorption processes. It was observed that diffusion coefficients (D(s)) for swelling obeyed the t(1/2) law and found to be correlated with the amount of chloroform content in the cell. Diffusion coefficients (D(d)) during desorption were also measured and found to be increased as the saturated chloroform vapor content is increased in the cell.