Russian Chemical Bulletin, International Edition, Vol. 57, No. 7, pp. 1351—1355, July, 2008 1351 Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1324—1329, July, 2008. Full Articles 1066-5285/08/5707-1351 © 2008 Springer Science+Business Media, Inc. Estimation of electrostriction coefficients of a nonlinear optical polymer electret M. Yu. Balakina A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Research Center of the Russian Academy of Sciences, 8 ul. Akad. Arbuzova, 420088 Kazan, Russian Federation. Fax: +7 (843) 273 2253. E-mail: marina@iopc.knc.ru, mbalakina@yandex.ru The effect of organic chromophores incorporated into a polymer electret and responsible for its nonlinear optical (NLO) response to an applied electric field on the electrostriction coefficients (ESC) of the material is studied. Analytical expressions for the ESC were derived in the framework of a model proposed earlier, which includes the effect of a locally anisotropic, polarizable and deformable environment on the electric characteristics of the chromophore. The dependence of the ESC on both macroscopic and microscopic parameters of the molecular system is established. Numerical estimates of the ESC for poly(methyl methacrylate) doped with the dye Disperse Red 1 and dimethylaminonitrostilbene-doped polycarbonate agree with experimental data in order of magnitude. The relations obtained can be used in the design of novel organic NLO materials. Key words: organic nonlinear optical materials, polymer electret, organic chromophore, non- linear optical response, electrostriction, local field, polarizability, hyperpolarizability. In the last two decades, the interest in novel polymer- ic materials possessing nonlinear optical (NLO) proper- ties has been increased considerably owing to possible applications of these materials in photonics and opto- electronics. 1—5 An NLO response of a polymeric materi- al is due to introduction of chromophore groups (molec- ular sources of the effect, e.g., organic molecules con- taining terminal donor and acceptor groups linked by a π-conjugated bridge 1—3 ). This structure ensures a fast electronic response of the molecular system to an applied external field. NLO chromophores are characterized by large dipole moments (~10 D) and hyperpolarizability, which can vary over a wide range depending on the molec- ular structure (for a detailed catalog of NLO chro- mophores and their electrical characteristics, see, e.g., Ref. 2). Examples of popular chromophores are provided by the dyes Disperse Red 1 (DR1) and dimethylamino- nitrostilbene (DANS). Manifestation of the so-called quadratic NLO re- sponse requires a transition of a molecularly doped poly- meric material to the electret state characterized by a nonzero constant ("frozen-in") polarization, which is also retained when the electric field is switched off. The design of a polymer electret involves orientation of incor- porated chromophore groups by external electric field applied to the material heated to a temperature above