Ordered Films by Alternating Polyelectrolyte Deposition of Cationic Side Chain and Anionic Main Chain Chromophoric Polymers

Abstract

Using the method of aqueous solution alternating polyelectrolyte deposition (APD), second-order nonlinear optical (NLO) polymer films were prepared for the first time in which both polymers were NLO-active. Films were prepared by alternately coating a solid substrate with an NLO-active side chain polycation and an NLO-active main chain polyanion. This new polyanion was comprised of α-cinnamoyl chromophores in the syndioregic configuration (an “accordion” polymer). The new polycation was derived from polyepichlorohydrin that was completely substituted with new stilbazolium side chain. The films were transparent and had no texture when observed by polarized microscopy. The increase in intensity of the second harmonic (SH) signal generated in the films was quadratic with each molecular layer to 20 layers. Beyond that, the SH signal intensity saturated as more layers were added.