Second-order nonlinear optical main-chain polymers by polymerization of poled monomers (original) (raw)
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Computational and …, 2012
A new class of p-spacer conjugated donor-acceptor polyoxometalate (POM) cluster covalently attached to the side chain of conjugated polymer, based on the strong electron-donating hexamolybdate pendant and an electron-withdrawing acceptor moiety (ANO 2 ), exhibits large second-order optical nonlinearity. For the first time, the effect of increasing the length of the polyenic p-spacer (AC"CA) in polymeric chain containing POM cluster and the influence of the nature of the acceptor moiety on the second-order nonlinear optical (NLO) properties have been studied by using the TDDFT calculations. An intense long range charge-transfer has been observed in these D-p-spacer conjugation -A compounds where the degree of the intramolecular charge transfer from the donor (hexamolybdate pendant) to the acceptor (end phenyl ring bearing ANO 2 moiety) has been enhanced through p-spacers which might be responsible for the large NLO responses. The conjugated polymers with POM (hexamolybdate) as side-chain pendant are anticipated to be better entrants for NLO applications as their large first hyperpolarizability make them attractive candidates for nonlinear optical materials. Such polymers may exhibit both efficient charge transfer and efficient charge transporting properties as increased conjugation is amplifying the NLO response. These features provide a rationale for the NLO response of these materials and are attractive for designing new, highly efficient second-order nonlinear optical inorganic-organic polymeric composites.
Electrical determination of the degree of cross-linking in a poled non-linear optical polymer
Chemical Physics Letters, 1996
A comparative investigation of the thermal dipole-orientation stability in a guest-host and a cross-linked non-linear optical polymer with similar structures of the polymer backbone is reported. Cross-linking yields a rigid polymer network with two types of dipoles: those already cross-linked and therefore thermally stable and those not as yet cross-linked and therefore fast relaxing. The combination of isothermal and thermally stimulated measurements allows for a complete characterization of dipole relaxation in the two sample polymers.
Synthesis and characterization of polymers for nonlinear optical applications
2003
A difunctional NLO Azo-Dye chromophore has been synthesized and polymerization has been performed with a comonomer bearing a side-chain epoxy group. Deposition of the polymer on glass substrates was performed by spin-coating, resulting in uniform films up to 2 μm thickness. The orientation of the chromophore was performed under a "pin-to-plane" positive corona discharge followed by a heat- treatment in order to obtain reticulation of the films. Molecular orientation has been investigated using UV-Vis. and Raman spectroscopy. Poling of the films results in a decay of absorbance as well as in a blue shift of the spectrum. At the same time, the 1600 cm-1 band disappears from the Raman spectra, indicating orientation of the chromophores. Cross-linking has been studied by FTIR and all-optical poling and showed an improved stability of the electro-optic thin films.
Polymer Journal, 1997
New second-order nonlinear optical main-chain polymers have been synthesized in very high yields by a two-stage Knoevenagel polycondensation from 3,6-diformyl-9-heptylcarbazole and bis(cyanoacetate)s. In these main-chain polymers, two kinds of nonlinear optical (NLO) chromophores, carbazole with two acceptor groups and 4'-nitrophenylazoaniline, were introduced in a slipped shoulder-to-shoulder arrangament. All polymers were determined to be amorphous and to have glass transition temperatures in the range of 134-l 58°C by a differential scanning calorimeter. The chloroform soluble main-chain polymers show very high weight and number average molecular weights measured by a gel permeation chromatography. Thin films of the polymers could be obtained by a spin coating method. The orientation of dipoles could be achieved by applying an electric field. These poled films show good reasonable and stable second-order nonlinear optical responses.
Characterization of a side chain polymer for second-order nonlinear optical properties
Journal of Polymer Science Part A: Polymer Chemistry, 1999
We report the characterization of copolymers of methyl methacrylate (MMA) and 2-propenoic acid, 2-methyl-, 2-[[[[4-methyl-3-[[(2-methyl-4-nitrophenyl)amino]carbonyl]aminophenyl]carbonyl]oxy]ethyl ester (PAMEE) exhibiting nonlinear optical (NLO) properties. The linear copolymer, poly(MMA-co-PAMEE), with a NLO chromophore incorporated into PAMME exhibits a high glass transition temperature of 131°C, as determined by DSC. The thin films of copolymers, which were cast on microscopic glass slides, were optically transparent, and the corona poled polymers produced relatively large and stable second harmonic generation (SHG) signals at room temperature. The nonlinear coefficient d 33 of the crosslinked copolymer containing 30 wt % PAMEE was 30.8 pm/V. The SHG signal strength remained unchanged, even after 120 days, and exhibited excellent thermal stability at 65°C.
Stability of NLO chromophores in doped polymer films during electric field poling
Journal of Physics D: Applied Physics, 1992
Thin films of organic polymsrs doped with specific chromophores may be used to exhibit substantial and useful second-order nonlinear optical phenomena. Such films must be subjected to DC electric field poling to eliminate the inherent inversion symmetry. In principle such poling processes may be monitored using w absorption spectroscopy. but there are many factors which lead to ambiguity in any interpretation. In particular we show that the electric field poling can result in ionic-current-induced chemical transformation cd the NLO chromophore to a NLO inactive moiety. Here we consider the stability of azo-based chromophores which are a common class of NLO chromophores. This electric field induced modification could lead to serious Overestimation of any poling effects using w spectroscopy and places limitations on potential technological applications. Such degradation does nat occur in materials prepared from polymers which contain chemically linked Chromophores.
Design, Methodology and Preparation of Novel Polymers for Nonlinear Optics
MRS Proceedings, 1997
One-pot post-polymerization modification reactions such as azo-coupling and tricyanovinylation reactions were employed to synthesize a series of polymers containing different nonlinear optical (NLO) chromophoric as well as ionic functionalities. We have extended and established the versatility of our earlier reported post-modification strategy to incorporate various heteroaromatic chromophores as well as ionic functionalities in the polymers, at the final stage of synthesis. The correlation between different heteroaromatic chromophore structures and the NLO properties of the polymers was extensively studied. Polymers containing heteroaromatic chromophores exhibit improved temporal stability and enhanced NLO activity. Polymers with ionic chromophores were employed to fabricate NLO active ultra-thin films using electrostatic selfassembling (ESA) technique. Attempts were also made to synthesize second order NLO active polydiacetylene derivatives using post azo-coupling reaction.