Nonlinear Optical Polyurethane Research Articles

Synthesis and properties of novel nonlinear optical polyurethane containing 4-(2′-carbomethoxy-2′-cyano)vinyl-5-nitrocatecholic group

ABSTRACTA new X-type polyurethane (5) containing 4-(2′-carbomethoxy-2′-cyano)vinyl-5-nitrocatecholic groups as NLO chromophores, which are components of the polymer backbone, was prepared. Polyurethane 5 is soluble in common organic solvents such as N,N-dimethylformamide and dimethylsulfoxide. It shows a thermal stability up to 280°C from thermogravimetric analysis with glass-transition temperature (Tg) obtained from differential scanning calorimetry near 93°C. The second harmonic generation (SHG) coefficient (d33) of a poled polymer film at the 1064 nm fundamental wavelength is around 6.58 × 10−9 esu. The dipole alignment exhibits a thermal stability even at 7°C higher than Tg, and no SHG decay was observed below 100°C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.

Synthesis and characterization of main‐chain, second‐order, nonlinear optical polyurethanes with isolation moieties and zigzag structures

ABSTRACTIn this study, two main‐chain second‐order nonlinear optical (NLO) polyurethanes were successfully prepared with indole‐based chromophores. The introduced phenyl isolation group and the continuous zigzag polymer backbone were found to be helpful for effectively decreasing the intermolecular dipole–dipole interactions and enhancing the NLO properties of the resulting polymers. The studied polymers exhibited good optical transparency, high thermal stability, and excellent NLO effects; this indicated that the nonlinearity–stability trade‐off and nonlinearity–transparency trade‐off could be alleviated by this newly designed polymer system. Poly{4‐anilinocarbonyl[N‐ethoxyl‐5‐phenyl‐3‐azo(2′‐oxyethylene‐4′‐nitrobenzene)indole]carbonylimino} with a zigzag backbone showed a large second harmonic generation coefficient (d33) value of 88.4 pm/V. However, poly{5‐naphthyliminocarbonyl[N‐ethoxyl‐5‐phenyl‐3‐azo(2′‐oxyethylene‐4′‐nitrobenzene)indole]carbonylimino} (PUAZN) with a continuous zigzag structure exhibited a higher d33 value of 116.2 pm/V, which was attributed to the unique rigid and zigzag linkage of 1,5‐naphthalene as the isolation spacer. The enhanced NLO efficiency and relatively longer term temporal stability made PUAZN as a promising candidate for practical applications in photonic devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42974.

Synthesis and Properties of Novel Nonlinear Optical Polyurethane Containing Nitrophenylazocatecholic Group

A novel Y-type polyurethane 3 containing 4-(4-nitrophenylazo)catecholic groups as nonlinear optical (NLO) chromophores was prepared and characterized. Polyurethane 3 is soluble in common organic solvents such as acetone and DMF. Polymer 3 shows a thermal stability up to 270°C from TGA thermogram and the T g value obtained from DSC thermogram is around 96°C. The second harmonic generation (SHG) coefficient (d 33) of poled polymer film at 1064 nm fundamental wavelength is 4.58 × 10−9 esu. The dipole alignment exhibits a thermal stability even at 4°C higher than T g, and there is no SHG decay below 100°C due to the partial main-chain character of the polymer structure, which is acceptable for nonlinear optical device applications.

Synthesis and nonlinear optical properties of novel y-type polyurethanes containing different concentrations of chromophore

A new series of Y-type polyurethanes containing different concentrations of nonlinear optical (NLO) chromophore with aniline donor and tricyanofurane (TCF) acceptor have been successfully prepared, and characterized by FTIR, UV-Vis, and 1H-NMR spectra. New polyurethanes were synthesized with different chromophore contents by introducing diol N, N-dihydroxyethylaniline or 4-[N, N-(dihydroxyethyl)amino]benzaldehyde. These NLO polyurethanes exhibit good film forming property and high thermal stability up to 281°C. The highest electro-optic coefficient (r33) of polymers is up to 39 pm V−1 measured by simple reflection technique at 1310 nm, and the temporal stability of the poling-induced order at elevated temperature of 80°C was much improved through the introducing of hydrogen bonding interaction in this system. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

New nonlinear optical polyurethanes with adjusted subtle structure through Sonogashira coupling reaction

AbstractIn this paper, four new nonlinear optical (NLO) polyurethanes (P1–P4) were designed and synthesized, and according to the concept of “suitable isolation group,” the subtle structure of the obtained polymers were modified by the introduction of isolation groups in different sizes to adjust their properties via Sonogashira coupling reaction. All the polymers were well characterized and the second harmonic generation (SHG) experiment results demonstrated that BOP groups were the suitable isolation groups in this system, and the corresponding polymer P2 exhibited a larger d33 value than other polymers. Thus, the obtained results further confirmed our original idea and were consistent with the concept of “suitable isolation group.” Copyright © 2009 John Wiley & Sons, Ltd.

Synthesis and Properties of Novel T-type Nonlinear Optical Polyurethane Containing Tricyanovinylthienyl Group with Enhanced Thermal Stability of Dipole Alignment

A novel T-type polyurethane 7 containing 1-(2,5-dioxyphenyl)-2-(5-(1,2,2-tricyanovinyl)-2-thienyl)ethenes as NLO chromophores, which constitute part of the polymer backbone, was prepared. Polyurethane 7 is soluble in common organic solvents such as DMF and DMSO. It shows a thermal stability up to <TEX>$270^{\circ}C$</TEX> from TGA thermogram with <TEX>$T_g$</TEX> value obtained from DSC thermogram near <TEX>$155^{\circ}C$</TEX>. The second harmonic generation (SHG) coefficient (<TEX>$d_{33}$</TEX>) of poled polymer film at 1560 nm fundamental wavelength is <TEX>$3.56{\times}10^{-9}$</TEX> esu. Polymer 7 exhibits a thermal stability even at <TEX>$5^{\circ}C$</TEX> higher than <TEX>$T_g$</TEX>, and no significant SHG decay is observed below <TEX>$160^{\circ}C$</TEX>, which is acceptable for nonlinear optical device applications.

Synthesis and nonlinear optical properties of a novel polyurethane containing cyanovinylthiophene with enhanced thermal stability of dipole alignment for electro‐optic applications

AbstractStabilization of electrically induced dipole alignment is one of the important criteria in the development of nonlinear optical (NLO) polymers for electro‐optic device applications. Polyurethanes for NLO applications have attracted attention because of their high thermal stability due to hydrogen bonding. In the work reported here, we designed and synthesized a new type of NLO polyurethane, in which the pendant NLO chromophores are part of the polymer backbone. This mid‐type NLO polymer is expected to have the merits of both main‐chain and side‐chain NLO polymers, namely stable dipole alignment and good solubility. 1‐[3,4‐Di‐(2‐hydroxyethoxy)phenyl]‐2‐(2‐thienyl)ethene was prepared and condensed with 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate to yield a polyurethane. This polyurethane was reacted with tetracyanoethylene to give a novel Y‐type polyurethane (7) containing 1‐(3,4‐dioxyphenyl)‐2‐[5‐(1,2,2‐tricyanovinyl)‐2‐thienyl]ethenes as NLO chromophores, which constitute part of the polymer backbone. Polyurethane 7 is soluble in common organic solvents such as N,N‐dimethylformamide and dimethylsulfoxide. It shows a thermal stability up to 280 °C from thermogravimetric analysis with a glass transition temperature obtained from differential scanning calorimetry of ca 162 °C. The second harmonic generation (SHG) coefficient (d33) of a poled polymer film of he polyurethane at 1560 nm fundamental wavelength is ca 1.11 × 10−18 C. Polymer 7 exhibits an enhanced thermal stability and no significant SHG decay is observed below 150 °C, which is acceptable for NLO device applications. Copyright © 2009 Society of Chemical Industry

Two Types of Nonlinear Optical Polyurethanes Containing the Same Isolation Groups: Syntheses, Optical Properties, and Influence of Binding Mode

In this paper, two new series of main-chain and side-chain second-order nonlinear optical (NLO) polyurethanes have been successfully prepared, in which isolation groups with different sizes were introduced to adjust the NLO property of the resultant polymers, according to the concept of "suitable isolation groups". The second harmonic generation (SHG) experiments demonstrated that all the polymers exhibited large second harmonic generation (SHG) coefficients of d33 values (up to 105.6 pm/V) with excellent thermal stability and film-forming ability, indicating that the introduction of isolation groups could alleviate the "nonlinearity-stability trade off" efficiently. In addition, for both main-chain and side-chain polymers, BOP acted as the suitable isolation group. It was also found that the positive influence of the linked suitable isolation spacer was more obvious in the main-chain polymers, in comparison with those in the side-chain polymers.

Synthesis of Novel Y-Type Nonlinear Optical Polyurethane Containing Tricyanovinylthiophene with High Thermal Stability of Dipole Alignment

A novel Y-type polyurethane 7 containing 1-(2,4-dioxyethoxy)phenyl-2-{5-(1,2,2-tricyanovinyl)-2-thiophenyl)}ethenyl groups as nonlinear optical (NLO)-chromophores, which are components of the polymer backbones, was prepared. Polyurethane 7 is soluble in common organic solvents such as DMF and DMSO. It showed a thermal stability up to 280°C in TGA thermogram and the T g value obtained from DSC thermogram was around 163°C. The second harmonic generation (SHG) coefficient (d 33 ) of poled polymer film at 1560 nm fundamental wavelength was around 3.72 × 10−9 esu. The dipole alignment exhibited a thermal stability up to near T g , and there was no SHG decay below 150°C due to the partial main-chain character of the polymer structure, which is acceptable for nonlinear optical device applications.

Controlling nonlinear optical effects of polyurethanes by adjusting isolation spacers through facile postfunctional polymer reactions

With the aim to control nonlinear optical (NLO) effects of polyurethanes, especially to efficiently translate the fixed μβ values of the organic chromophore to possibly higher macroscopic NLO activities of polymers, a facile synthetic strategy, consisting of the postazo coupling and esterification reactions, was developed to prepare a series of second-order nonlinear optical polyurethanes ( P2– P5). And in the polymers, different isolation groups were introduced to the sulfonyl-based chromophore moieties at the acceptor side. Thus, polyurethane P1 containing aniline groups was obtained from the copolymerization of 2,4-toluenediisocyanate (TDI) and N, N-2-(2-hydroxyethyl)aniline directly; then a postazo coupling reaction of p-(2-hydroxyethyl)sulfonylbenzenediazonium fluoroborate toward the aniline ring afforded the sulfonyl-based chromphore-functionalized polyurethane P2, which underwent the subsequent esterification reactions between the hydroxyl groups in P2 and different organic acids to link different isolation spacers (changing from small groups to much larger ones such as carbazolyl groups), to the chromophore moieties at the acceptor side, to yield polyurethanes P3, P4 and P5. The polymers exhibit good solubility in common organic solvents and are thermally stable. The maximum absorption appeared at about 436 nm with a cutoff at ca. 570 nm, resulting in a wider transparency window. The tested NLO properties demonstrate that the resonant d 33 values of polymers could be improved about 1.5 times by attaching isolation spacers with suitable bulkiness.

Synthesis and characterization of second-order nonlinear optical polyurethane with high thermal stability

A second-order nonlinear optical polyurethane was formed with an X-type multi-dimensional charge-transfer (CT) chromophore (DNPIPDHPI) and 3,3 ′-dimethoxy-4,4 ′-diphenyl diisocyanate. Simultaneous poling and polymerization and in situ second harmonic generation (SHG) measurement technique was carried on to evaluate the thermal stability of the poling induced orientation. The SHG signal of the poled polymer film was not decay below 150 °C and remains 90% of relative d 33 value at 200 °C, which is better than the results reported in literature. Comparison of thermal stability indicates that the X-type chromophores possess better property in controlling the decay of the SHG activity than classic chromophores.

Synthesis and characterization of a novel nonlinear optical polyurethane polymer

A cross-linked polyurethane with a novel nonlinear optical (NLO) chromophore [2-(4 ′- N, N-dihydroxyethylphenylazo)-3,5-dinitrothiophene] covalently incorporated for second-order optical nonlinearity was developed. High optical-quality films can be obtained from the prepared polymer. Resonance-enhanced second-harmonic coefficient ( d 33) of 66 pm V −1 at 1.064 μm fundamental wavelength of the poled films was obtained. Test on temporal stability shows that when the films were kept in an oven at 100°C for 1000 h in air, 75% of the NLO signal still remained.

A Nonlinear Optical Polyurethane Functionalized with a Heteroaromatic Thiophene Ring Having a Tricyanovinyl Group

A new functionalized polyurethane structure with a thiophene ring having a tricyanovinyl group in the polymer side chain was synthesized. The molecular weight of the final polymer was determined to be Mn=12000 and Mw/Mn=2.04. The resulting polymer was soluble in N-methylpyrrolidinone and could be processed into good optical quality films by spin casting at ca. 100°C. It showed no weight loss up to 266°C in the thermogravimetric analysis and a definite glass transition at 176°C. The second-order nonlinear optical coefficient, d33, was determined to be 51 pm V-1 from measuring the second harmonic generation (SHG) for a thin polymer film after poling treatment. The outstanding orientational stability of the aligned chromophores was observed up to about 150°C, which originated from the rigid polymer backbone and the stabilizing function of the hydrogen bridges formed between the neighboring polyurethane chains.

Nonlinear optical polymers with novel benzoxazole chromophores: V. Linear and crosslinked polyurethanes using nitrothiophene and nitrophenol as electron acceptors

We synthesized two new diol monomers with benzoxazole-based nonlinear optical (NLO) chromophores, one of which has an additional hydroxyl group as a crosslinkable moiety and the other has a nitrothiophene group as an electron withdrawing unit. The diol monomers were polymerized with 4,4′-methylenebis(phenyl isocyanate) to give NLO polyurethanes, respectively. Linear polyurethane with hydroxyl groups could be crosslinked between side chain chromophores themselves after poling using an additional crosslinking agent such as teramethyl-1,3-xylylene diisocyanate. Temporal stability of electro-optic coefficient of a crosslinked polyurethane was improved compared with that of a linear polyurethane. The second harmonic generation coefficient of linear polyurethane with benzoxazole–thiophene chromophores was 94 pm V −1 (1.064 μm) and nonresonant d 33 value was 17.1 pm V −1 calculated by two-level model equation.

Two-step refractive index changes by photoisomerization and photobleaching processes in the films of non-linear optical polyurethanes and a urethane–urea copolymer

Photoinduced refractive index and absorption spectrum changes in the films of polyurethanes and a urethane-urea copolymer with large second-order non-linear coefficient d have been studied. These changes were explained by a two-step reaction scheme including a trans–cis photoisomerization followed by a photobleaching reaction. The former process was reversible and the latter was irreversible, so that a thermally stable refractive index was obtained. The changes were accelerated by heating. A channel waveguide was fabricated by the processes and light propagation through the waveguide was observed.

Fabry-Pérot interferometry applied to the study of piezoelectric and electro-optical properties of a poled NLO polyurethane

An improved Fabry-Pérot interferometric technique for the in situ measurement of electrooptical coefficients, piezoelectric coefficient and birefringence of nonlinear optical (NLO) polymer films has been developed. The measurements can be done conveniently on polymer films maintained under inert gas or vacuum and at temperatures up to 200°C. The technique has been applied to the characterisation and disorientation study of an inhouse synthesised azo dye-containing polyurethane exhibiting a glass transition temperature at 143°C and having an electrooptical coefficient r 33 of 18 pm/V at 830 nm after poling under 100 V/μm. The uncertainty on the electrooptical coefficients was found to be 4% on r 13 and 8% on r 33 but raises up to 25% for the piezoelectric coefficient d which is negative and about 10% of r 33. For poling fields E p less than 50 V/μm, r 13, r 33 and d vary linearly with E p but r 33 increases more than linearly for higher poling fields. The ratio r 33/ r 13 is greater than 3 and raises up to 5 after poling under 120 V/μm. The rate of disorientation of the chromophores in the polymer matrix at elevated temperatures follows approximately stretched exponentials and is weakly dependent on the poling field in the range 25–92 V/μm. Our experimental results are compared to values deduced from various theoretical models such as the isotropic and the Van der Vorst-Picken models. None of them are entirely satisfactory.

Thermosetting nonlinear optical polymer: Polyurethane with disperse red 19 side groups

A new thermosetting second-order nonlinear optical polyurethane polymer with disperse red 19 pendant groups was studied by second-harmonic generation and electro-optic modulation methods. The polymer can be crosslinked by thermal curing during electric field poling. The electro-optic coefficient r13 measured with a Mach–Zehnder interferometer ranged from 5 pm/V at 800 nm to 13 pm/V at 633 nm. The polymer crosslinked during poling showed no significant decay of the nonlinearity at room temperature for thousands of hours. A long-term thermal stability of the dipole alignment at an elevated temperature, 90 °C, was demonstrated. The thermosetting polymer showed improved alignment stability under ultraviolet exposure.