Polymers with nonlinear optical properties and high glass transition temperatures by functionalization of reactive precursors (original) (raw)
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Macromolecules, 1998
A new reactive copolymer system with high, but still variable glass-transition temperatures was synthesized. This was accomplished by copolymerizing various N-substituted maleimides with methylvinyl or vinyl isocyanate, so that a polymer with a 1:1 composition of the two monomers is obtained. Further functionalization is then possible with any nucleophile known from comparable low molecular weight reactions. With different substituents attached to the imide-ring, T g can be adjusted between 120 and 210°C. Two effects of the substituent at the imide nitrogen are observed. Bulky groups reduce the mobility of the chain and lead to high Tg values. A similar tendency is found for smaller, less flexible substituents. In this case, the inter-and intramolecular forces of hydrogen-bonding (urethanes) contribute to the effects for high Tg's. The potential of these copolymers was highlighted here for NLO chromophores. A variety of different NLO chromophores was attached to the polymer backbone by reaction of a hydroxyalkyl-containing chromophore with the isocyanate groups, thereby forming urethane linkages between chromophore and polymer. The polymers functionalized in this way show nearly unchanged glass transition temperatures and offer thus the possibility to prepare NLO polymers with high T g values and good solubility. It is important that even base labile NLO chromophores and systems labile to radical conditions can be fixed easily. The advantage of this system is highlighted by the fixation of NLO chromophores with tricyanovinyl (C2), tricyanochinodimethane (C3) and heterocyclic acceptors (C4). With one of these systems a d 33 value of 53 pm/V could be obtained for a loading with only 12 wt % of chromophore.
Polymer, 2001
Nonlinear optical polymers with high glass transition temperatures were prepared by covalent functionalisation of polymaleimide copolymers with hydroxyalkyl chromophores via the Mitsunobu reaction. The polymaleimides were obtained by radical polymerisation of maleimide with 4-phenylstyrene (PM1), indene (PM2) or 1-adamantylmethacrylate (PM3). Glass transition temperatures in the range of 222±2888C were obtained. Thin spincoated ®lms of the polymers were corona-poled and analysed by second-harmonic generation; secondorder susceptibility values (d 33 ) up to 16 pm/V were obtained. Poled order stability measurements over periods of more than 200 h resulted in 72±90% of remaining NLO-response at 1258C. q
Journal of Polymer Science Part A: Polymer Chemistry, 1991
Optically active copolymers of (-)-menthyl acrylate (MtA) with racemic ~-methylolbenzoin methyl ether acrylate (MBA) as well as of (-)-menthyl vinyl ether (MtVE) with racemic ct-vinyloxymethylbenzoin methyl ether (MBVE) have been prepared by radical and cationic initiation, respectively. The reactivity of comonomers as well as spectroscopic and fractionation data suggest that acrylic and vinyl ether copolymers show a tendency towards substantial random and block distributions of monomeric units, respectively. Optical activity at 589 nm of the copolymers seems to exclude any stereoselectivity and stereoelectivity during the copolymerization in both systems. Chiroptical properties indicate that in both series of copolymers an induced optical activity on benzoin-derivative chromophores occurs, which is due to a dissymmetric arrangement of the macromolecules. Circular dichroism data, connected with the n ~ n* electronic transition of the keto group, suggest that the observed ellipticity in MBA/MtA copolymers is substantially due to isolated MBA units. In the case of MBVE/MtVE copolymers both isolated and sequential MBVE units give a contribution to the ellipticity, thus suggesting that the induced optical activity is transmitted through short blocks of MBVE units.
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.
Macromolecular Symposia, 2006
Novel optically active homopolymeric polymethacrylates have been synthesized by radical polymerization of the corresponding monomers (S)-3-methacryloyloxy-1-(4-azobenzene)pyrrolidine and (S)-3-methacryloyloxy-1-(4 H -nitro-4-azobenzene)pyrrolidine. The polymers are characterized by the presence in the side chain of an optically active chiral moiety linked to the trans-azoaromatic system through the pyrrolidine nitrogen atom, which allows the establishment of a donor±acceptor conjugated system. The thermal properties of the polymeric derivatives indicate an appreciable thermal stability and increased glass transition temperature values with respect to similar polymeric derivatives bearing in the side chain the conjugated trans-azoaromatic chromophore. UV and circular dichroism spectra in solution suggest that dipolar interactions between the chromophores are present in the polymeric derivatives and that the macromolecules assume for chain sections dissymmetric conformations with a prevailing screw sense, induced by the presence of the conformationally rigid optically active cyclic moiety. This gives rise to much higher optical activity of the macromolecular systems with respect to that afforded by the structurally related low molecular weight compounds synthesized as models of the polymer repeating units, despite the low stereoregularity degree of the polymeric main chain. #
Chemistry of Materials, 2006
The electric-field-dependent change in refractive index in nonlinear optical (NLO) materials can be utilized for electrical-to-optical signal conversion, such as fast electrooptic (EO) modulators needed in optical telecommunication. 1 Compared to inorganic NLO crystals (e.g., LiNbO 3 ), organic NLO materials offer advantages such as higher EO coefficients, lower dielectric constants, and good processibility. 2 To obtain a large EO response, chromophores with a high molecular nonlinearity (hyperpolarizability ) need to be oriented to form a macroscopically noncentrosymmetric material. For chromophores with a large dipole moment (µ), one way to achieve such a polar ordering is by electric-field poling of the chromophores in a polymer matrix. Consequently, the main figure of merit describing the performance of NLO chromophores in such EO polymer applications is the scalar product µ . Among many types of organic NLO chromophores, zwitterionic derivatives of 7,7,8,8-tetracyanoquinodimethane (TCNQ) such as (Z)-4-[1-cyano-3-(diethylamino)-2-propenylidene]-2,5-cyclohexadiene-1-ylidenepropanedinitrile (DEMI; ) are known to possess very high molecular hyperpolarizabilities and show the largest µ values reported to date. 3 To be useful for EO applications, the chromophores need to be either doped in a medium (e.g., polymer or sol-gel glass) or covalently linked to a polymer and oriented under an electric field. While the zwitterionic nature of the NLO chromophores is in favor of attaining a large µ value, it can also present limitations for EO applications as a result of poor solubility and strong dipole-dipole interactions. For example, DEMI was reported to have a high µ 0 value of 9500 × 10 -48 esu ( 0 ) static hyperpolarizability). 3 An analogue, picolinium quinodimethane (PQDM) 2a ( , was calculated to have a static molecular hyperpolarizability of 1270 × 10 -30 esu. 4 However, both chromophores are highly crystalline and have no functional groups (e.g., OH or NH 2 ), making it very difficult to either physically or chemically incorporate them into a host polymer.
New NLO active cyclopalladated chromophores in main-chain polymers
Four new OH-functionalized orthopalladated complexes bearing an electron-donor and an acceptor group in a trans-like arrangement with respect to the metal have been prepared and characterized. The ligands are Schiff bases, bound as C,N-or N, O-chelating moieties. Four new polyesters were obtained by polycondensation from the monomeric complexes and pentyloxyterephthaloyl chloride. Two ''model'' complexes, each one related to one monomer, were also synthetized, in order to obtain further and more detailed characterization data, and in particular to perform measurements of lb.
Synthesis of Non-linear Optical Polymer of Azo Coumarin-pyrimidine Based Chromophore
Diazonium salt was prepared by dissolving 2-amino-5-nitro pyrimidine with sodium nitrite and sulphuric acid in presenceof water. The temperature was maintained up to 5 0 c. The solution was kept for 15 minutes with occasional stirring to complete the diazotization. Then diazonium salt was poured into the ice-cold solution of 8-hydroxy-4-methylcoumarin in 20ml of 10% sodium hydroxide solution and kept for 1h at 0 0-5 0 c. The pH was maintained up to 5-6. 5-(5-nitro pyrimidinylazo)-8-(1-hydroxy hexyl oxy)-4-methyl coumarin was synthesized by treating 5-(5-nitro pyrimidinylazo)-8-hydroxy-4-methyl coumarin with 1-chloro-6-hydroxy hexane in the presence of potassium hydroxide and potassium iodide in the solvent medium of DMSOat 80 0 c for 20h. The vinyl monomer was synthesized by the treatment of 5-(5-nitro pyrimidinyl azo-8-(1-hydroxy hexyl oxy)-4-methyl coumarin with methacryloyl chloride in the solvent medium of THF. Lastly, the copolymer was synthesized by the treatment of vinyl monomer with MMA in presence of radical initiator AIBN in the solvent medium of DMF at 60 0 c for 2 days. The monomer and copolymer were characterized by IR, UV and NMR spectra.