Guest-host polymers, nonlinear optics

Stahelin, M., Walsh, C. A., Borland, D. M., Miller, R. D., Twieg, R. J., and Volksen, W. Orientational decay in poled 2nd-order nonlinear-optical guest-host polymers Temperature dependence and effects of poling geometry. J. Appl. Phys. vol. 73 (no. 12), 15 [une 1993, p. 8471-8479. 

Abstract The orientation of the nonlinear optical chromophore in a guest-host polymer system... 

This chapter concentrates on the design of efficient dipolar NLO chromophores and the different approaches for their incorporation in non-centrosymmetric materials, including guest-host polymer systems, chromophore-functionalized polymers (side-chain and main-chain), cross-linked chromophore-macromolecule matrices, dendrimers, and intrinsically acentric self-assembled chromophoric superlattices. The different architectures will be compared together with the requirements (e.g., large EO coefficient, low optical absorption, high stability, and processability) for their incorporation into practical EO devices. First, a brief introduction to nonlinear optics is presented. 

Zhou, Y., L. Shaojun, and Y. Cheng. 2003. Poling properties of guest-host polymer films of X-type nonlinear optical chromophores. Synth Met 147 519-1520. 

Side-chain polymers are significantly more stable to electric field poling-induced nonlinear optical effects than those of guest-host polymers, but still suffer from slow relaxation of field-induced noncentrosymmetric alignment and, hence, the nonlinearity. 

A novel second-order nonlinear optical medium which should offer considerable fabrication flexibility has been described. The physics of alignment of the highly nonlinearly polarizable moiety was discussed. However, observation of complex dynamical and thermal behavior indicates that an important role is played by the polymer liquid crystalline host. Additional properties of modified members of this family of lc polymers were consequently investigated. The explanations of guest alignment stabilization and thermal dependence of the alignability remain unresolved issues. 

As discussed earlier, while the scale of the fillers is substantially different, nanocomposite materials concepts and technology are very similar to those of conventional composite materials. This is clearly demonstrated in the case of new thermosets for nonlinear optical (NLO) applications, " " where nanocomposite of liquid crystalline thermosets, IPNs, and simple filled thermosets are evaluated. Tripathy et al. discussed four different ways to prepare nonlinear optical polymers. (1) The polymer matrix is doped with NLO moieties in a guest/host system (2) In side-chain polymer systems, NLO polymers with active moieties are covalently bonded as pendant groups (3) In the main chain polymer, the chromo-phores are incorporated as parts of the main polymer backbone to enhance the temporal stability of the NLO properties and (4) Stability of the optical noninearity in sol-gel-based thermosets is related to... 

Kim, W.-K., Hayden, L.M. Fully atomistic modeling of an electric field poled guest-host nonlinear optical polymer, J. Chem. Phys. Ill, 5212-5222 (1999)... 

Barto, R.R., Jr., P.V. Bedworth, C.W. Frank, S. Ermer, and R.E. Taylor. 2005. Near-infrared optical-absorption behavior in high-beta nonlinear optical chromophore-polymer guest-host materials. II. Dye spacer length effects in an amorphous polycarbonate copolymer host. J Chem Phys 122 234907 1-14. 

Extensive studies have been made on poled NLO guest-host systems . The limited solubility of the NLO species in a host matrix and the thermal relaxation of the induced nonlinear optical activity of the poled polymeric films are major disadvantages. Side chain polymers have attracted attention since a large number of NLO molecules may be covalently attached to the polymer chain and the problem of phase segregation of the NLO component is alleviated. In this article, we present the second and third order NLO properties of a new class of guest-host system which possess excellent doping features and photoreactive characteristics. 

In guest/host PR polymers the macroscopic nonlinear optical properties result from the molecular constants of the dopant molecule (also called dinmiophore). Chromophores for nonlinear optical properties are usually based upon aromatic ra-electron systems unsymmetrically eiid-capped with electncm donat and electron accepting groups, as shown in Fig. 3. The molecular polarization of such molecules is a nonlinear fonction of the electric field and can be simplified to (4,5) ... 

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