Chromophores nonlinear optics, polymer incorporation

Makowska-Janusik, M., Reis, H., Papadopoulos, M.G., Economou, I.G., Zacharopoulos, N. Molecular dynamics simulations of electric field poled nonlinear optical chromophores incorporated in a polymer matrix, J. Phys. Chem. B 108(2), 588-596 (2004)... 

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. 

The linear and nonlinear optical behaviors of poly-(1,6-heptadiyne)s containing NLO chromophores was summarized in Table 22. It was found that n of the copolymers gave higher values than that of poly-76 not bearing any chromophore while the values of Amax were similar to each other. This result clearly shows the effects of incorporation of chromophore into the polymer backbone. The values of electrooptic coefficients, r33, for poled film samples of poly-77 to poly-81 by using a simple reflection technique reported by Teng et al. was measured. Table 22 shows the measured electrooptic coefficients of polymer films at... 

A method utilizing differential scanning calorimetry has been developed for quick and reproducible estimation of the thermal stability of nonlmear optical chromophores under consideration for incorporation into polymers for use in second-order nonlinear optical devices. The mediod which uses sealed glass ampoules has been used to compare a large number of chromophores and has been compared to electric field-induced second harmonic generation methods. 

It was shown that the thermal stability of conventionally formed polyimide polymers and copolymers (bearing nonlinear optical chromophores) is adequate for numerous device applications. There is a problems, however, with doped systems in that they tend to undergo phase separation. This limits the amount of the nonlinear optics chromophore that can be incorporated into the system. To try and make doping unnecessary, multifunctional polymers were synthesized that contain all the necessary components. One limitation of this technology, however, is the small nonlinear optical response (r33) values for many such poiyimides. This is not true of all of them. 

Historically, polymeric nonlinear optical materials have ranged from chromophores physically incorporated (i.e., dissolved) in polymer hosts to form composite materials, to chromophores attached by a single covalent bond to a polymer backbone, to chromophores attached at both ends to a polymer network. The physical incorporation of chromophores into polymer hosts to form composites typically... 

For nonlinear optical molecules which do not possess the desired centrosymmetric crystallization, there are very potent methods to incorporate these chromophores into polymer hosts ( electric field poling ) (Singer et al., 1986,1987 Hubbard et al., 1989 Bjorklund et al., 1991), self-assembly of molecular layers (Li et al., 1990 Katz et al., 1991), and Langmuir-Blodgett assembly of films (Roberts et al 1990 Kajikawa et al., 1992 Marder et al., 1994). 

In the following sections we describe the preparation of polymers which incorporated DEC chromophores either as components of a polymer backbone which is stabilized by interchain crosslinking or as a pendant to mainchain poljmers where the DEC chromophore is acting as the interchain crosslinking agent. The objective of this research, which has been realized, is the retention of significant optical nonlinearity at elevated temperatures (e.g., 125 °C) for extended periods of time. This is accomplished with the realization of an acceptable magnitude of optical nonlinearity (x(2) = 100-300 pnVV). 

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