2ND-HARMONIC GENERATION IN CARBON-DIOXIDE PROCESSED THIN POLYMER-FILMS

Polymer films were swelled with carbon dioxide (CO2), allowing the ali gnment of second harmonic generating (SHG) chromophores with an electr ic field at ambient temperatures. SHG decay provided information on th e glassy structure, the alteration of the glassy structure by a CO2 so rption-desorption cycle, and molecular motion in a glassy polymer matr ix. The host-guest system of poly(methyl methacrylate)-Disperse Red 1 was studied in most of the experiments; polycarbonate films were also examined. Chromophore alignment was less stable when either high CO2 p ressure or fast CO2 desorption was used. After chromophore alignment, the films exhibited a multimodal decay of second harmonic generation c apability. A fast decay was followed by a slow decay hypothesized to d epend on the alpha-relaxation.