Nonlinear activity and long-term stability of thin polymer films based on poly(3,5,7,3′,4′-pentahydroxyflavone-8-sulfonic acid) sodium salt

Abstract

Cross-linked polymers with chromophore fragments built-in main chains can, depending on their structure and synthesis conditions, keep during a long time the orientation of chromophores that is necessary to create new organic polymer materials demonstrating nonlinear optical properties. The present work is devoted to cross-linked polymers on the basis of di-, tri-, and tetraglycidyl ethers of quercetin-8-sulfonic acid sodium salt (3,5,7,3′,4′-penthahydroxyflavon-8-sulfonic acid sodium salt) which were synthesized, and then, poled in electrical field of corona discharge. Study of thermal, optical, and nonlinear optical parameters of the polymer films was carried out. It was found that the polymers obtained from di- and triglycidyl ethers of quercetin-8-sulfonic acid sodium salt are characterized by the higher values of macroscopic quadratic susceptibilities comparing with such a value for polymer obtained from tetraglycidyl ether of quercetin-8-sulfonic acid sodium salt. However, the latter polymer demonstrates a minimal intensity of relaxation processes that evidence its highest long-term stability, and thus, could be used as a nonlinear optical material. It is supposed that the difference of the nonlinear optical properties is due to peculiarities of intermolecular interactions in physical network of the polymers, namely, to the difference between numbers of hydrogen bonds formed by hydroxyl groups of chromophore fragments and number of hydrogen bonds linked of inter fragmental parts of the polymeric chains.