Synthesis and nonlinear optical properties of a novel X‐type polyester containing dicyanovinylnitroresorcinoxy groups with enhanced thermal stability of dipole alignment

A novel X‐type polyester (5) containing 4‐(2′,2′‐dicyanovinyl)‐6‐nitroresorcinoxy groups as nonlinear optical (NLO) chromophores, which constitute parts of the polymer backbone, was prepared and characterized. Polyester 5 is soluble in common organic solvents such as N,N‐dimethylformamide and acetone. Polyester 5 shows thermal stability up to 300 °C from thermogravimetric analysis with a glass transition temperature obtained from differential scanning calorimetry of near 108 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer films at the 1064 nm fundamental wavelength is 2.99 pm V^?1. The dipole alignment exhibits thermal stability even at 7 °C above the glass transition temperature, and no significant SHG decay is observed below 115 °C due to the partial main‐chain character of the polymer structure, which is acceptable for NLO device applications. © 2013 Society of Chemical Industry     

Preparation and electro‐optic properties of novel Y‐type polyimides with highly enhanced thermal stability of second harmonic generation

BACKGROUND: In the development of nonlinear optical (NLO) polymers for electro‐optic device applications, stabilization of electrically induced dipole alignment is one of the important criteria. Polyimides for NLO applications have attracted attention because of their high T_g values and high thermal stability. In this work we designed and synthesized a new type of NLO polyimide, in which the pendant NLO chromophores are parts of the polymer backbone. These mid‐type NLO polymers are expected to have the merits of both main‐chain and side‐chain NLO polymers: stabilization of dipole alignment and good solubility. RESULTS: 3,4‐Bis‐(3,4‐dicarboxyphenylcarboxyethoxy)‐4′‐nitrostilbene dianhydride was prepared and reacted with the corresponding aromatic diamine to yield unprecedented Y‐type polyimides containing 3,4‐dioxynitrostilbenyl groups as NLO chromophores, which constituted parts of the polymer backbones. The resulting polyimides are soluble in polar solvents such as dimethylformamide and dimethylsulfoxide. These polymers showed a thermal stability up to 320 °C in thermogravimetric thermograms with T_g values obtained from differential scanning calorimetry thermograms in the range 143–164 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at the 1064 nm^?1 fundamental wavelength were around 9.45 × 10^?18 C. CONCLUSION: The dipole alignment exhibited exceptionally high thermal stability even at 30 °C higher than T_g. There was no SHG decay below 180–190 °C because of the partial main‐chain character of the polymer structure, which is acceptable for NLO device applications. Copyright © 2007 Society of Chemical Industry     

Synthesis and electro‐optical properties of novel Y‐type polyurethanes containing dioxynitrostilbene

3,4‐Di‐(2′‐hydroxyethoxy)‐4′‐nitrostilbene (2) was prepared by the reaction of 2‐iodoethanol with 3,4‐dihydroxy‐4′‐nitrostilbene. Diol 2 was condensed with 2,4‐toluenediisocyanate, 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate and 1,6‐hexamethylenediisocyanate to yield novel Y‐type polyurethanes 3–5 containing dioxynitrostilbene as a non‐linear optical (NLO)‐chromophore. Polymers 3–5 were soluble in common organic solvents, such as acetone and DMF. These polymers showed thermal stability up to 280 °C in TGA thermograms with T_g values in the range of 100–143 °C in DSC thermograms. The approximate lengths of aligned NLO‐chromophores of the polymers estimated from AFM images were around 2 nm. The SHG coefficients (d₃₃) of poled polymer films were around 4.5 × 10^?8 esu. Poled polymer films had improved temporal and long‐term thermal stability owing to the hydrogen bonding of urethane linkage and the main‐chain character of the polymer structure, which are acceptable for NLO device applications. Copyright © 2004 Society of Chemical Industry     

Synthesis and nonlinear optical properties of novel Y‐type polyurethane containing nitrothiazolylazoresorcinoxy groups with highly enhanced thermal stability of second harmonic generation

Novel Y‐type polyurethane 4 containing 4‐(5‐nitro‐2‐thiazolylazo)resorcinoxy groups as nonlinear optical (NLO) chromophores, which are parts of the polymer main chains, was prepared and characterized. Polyurethane 4 is soluble in common organic solvents such as N,N‐dimethylformamide and dimethylsulfoxide. It shows thermal stability up to 280 °C as determined from thermogravimetric analysis with a glass transition temperature obtained from differential scanning calorimetry of about 126 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at 1064 nm fundamental wavelength is 3.78 pm V^?1. Polymer 4 exhibits thermal stability even at 4 °C higher than glass transition temperature, and no significant SHG decay is observed below 130 °C, which is acceptable for NLO device applications. © 2016 Society of Chemical Industry     

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

Stabilization 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     

Molecular design,synthesis, and electro‐optic properties of novel Y‐type polyesters with high thermal stability of second harmonic generation

3,4‐Di‐(2′‐hydroxyethoxy)‐4′‐nitrostilbene was prepared and condensed with terephthaloyl chloride, adipoyl chloride, and sebacoyl chloride to yield novel Y‐type polyesters containing NLO‐chromophore dioxynitrostilbenyl groups, which constituted parts of the polymer backbone. Polymers were found soluble in common organic solvents such as acetone and N,N‐dimethylformamide. They showed thermal stability up to 300 °C in thermogravimetric analysis with glass‐transition temperatures obtained from differential scanning calorimetry in the range 110–152 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at a 1064 cm^?1 fundamental wavelength were around 3.51 × 10^?8 esu. The dipole alignment exhibited high thermal stability even at 10 °C higher than the glass‐transition temperature, and there was no SHG decay below 120 °C for one of these polymers due to the partial main‐chain character of polymer structure, which was acceptable for NLO device applications. Copyright © 2005 Society of Chemical Industry     

Synthesis and electro‐optic properties of novel polyurethane containing the nitrophenylazoresorcinoxy group

A novel Y‐type polyurethane (polyurethane 3) containing 4‐(4‐nitrophenylazo)resorcinoxy groups as nonlinear optical (NLO) chromophores, which constitute part of the polymer backbone, was prepared and characterized. Polyurethane 3 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It shows thermal stability up to 270 °C from thermogravimetric analysis with a glass transition temperature obtained from differential scanning calorimetry of 102 °C. The second harmonic generation (SHG) coefficient (d₃₃) of the poled polymer film at 1064 nm fundamental wavelength is 2.06 pm V^?1. Polymer 3 exhibits thermal stability up to T_g, and no significant SHG decay is observed below 100 °C, which is acceptable for nonlinear optical device applications. Copyright © 2012 Society of Chemical Industry     

Synthesis of novel poly(vinyl ether)s containing the oxybenzylidenemalononitrile group as a nonlinear optical chromophore,and their electro‐optic properties

2,4‐Di‐(2′,2′‐dicyanovinyl)‐1‐(2′‐vinyloxyethoxy)benzene and 2,4‐di‐(2′‐carbomethoxy‐2′‐cyanovinyl)‐1‐(2′‐vinyloxyethoxy)benzene were prepared by condensation of 4‐(2′‐vinyloxyethoxy)isophthaldehyde with malononitrile and methyl cyanoacetate, respectively. The two vinyl monomers were polymerized with boron trifluoride etherate as a cationic initiator to yield poly(vinyl ether)s containing two oxybenzylidenemalononitrile and oxybenzylidenecyanoacetate groups, which are effective chromophores for second‐order nonlinear optical applications. These polymers were soluble in common organic solvents such as acetone and dimethyl sulforide. They showed thermal stabilities up to 300 °C from thermogravimetric analysis (TGA), with differential scanning calorimeter (DSC) thermograms giving T_g values in the range 73–87 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films were around 1.8 × 10^?9 esu, and these polymers showed good long‐term thermal stability for 60 days at room temperature, which is acceptable for nonlinear optical (NLO) device applications. Copyright © 2004 Society of Chemical Industry     

Synthesis of novel T-type nonlinear optical polyester with enhanced thermal stability of second harmonic generation for electro-optic applications

2,5-Di-(2′-hydroxyethoxy)benzylidenemalononitrile (3) was prepared and condensed with terephthaloyl chloride to yield novel T-type polyester (4) containing 2,5-dioxybenzylidenemalononitrile groups as NLO-chromophores, which are parts of the polymer backbones. The resulting polymer 4 was soluble in common organic solvents such as acetone and DMF and showed thermal stability up to 280 °C with T _g of 83 °C. The second harmonic generation (SHG) coefficient (d ₃₃) of poled polymer film at the 1,064 nm fundamental wavelength was around 4.46 × 10⁻⁹ esu. The dipole alignment exhibited high thermal stability even at 10 °C higher than T _g, and there was no SHG decay below 95 °C due to the partial main-chain character of polymer structure, which was acceptable for NLO device applications.     

Synthesis and characterization of two novel functional ladder-like polysilsesquioxanes for nonlinear optical response

Two novel functional ladder-like polysilsesquioxanes with double-chain macromolecular backbones and nonlinear optical (NLO) chromophore-containing side chains for NLO applications (NLO-T₁ and NLO-T₂) were synthesized successfully for the first time via the introduction of the NLO chromophores to the side chains of the ladderlike polychloropropylsilsesquioxane (Cl-T₁) and ladderlike poly(4-chloromethylphenyl)ethylsilsesquioxane (Cl-T₂), respectively, by an etherification reaction. The obtained polymers were characterized by FTIR, ¹H NMR, ¹³C NMR, ²⁹Si NMR, X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vapour pressure osmometry (VPO), fluorescence spectroscopy and second-harmonic generation (SHG) measurements. The poled thin films of the above two ladder-like NLO polymers showed d₃₃ coefficients of 9.2 and 9.6 pm V⁻¹, respectively. Compared with the corresponding single main chain polymers, the poled thin films of the synthesized ladder-like NLO polymers demonstrated a much higher thermal stability of SHG.     

Thermally stable maleimide copolymer for second-order nonlinear optics

Second-order nonlinear optical copolymer containing p-hydroxyphenyl maleimide as a comonomer was newly synthesized. Second-order nonlinear optical properties of the poled films were investigated in terms of the second harmonic generation (SHG) and linear electrooptic (EO) coefficient measurement. SHG coefficient, d₃₃ was found to be 14 pm/V at the fundamental wavelength of 1064 nm and EO coefficient, r₃₃ was found to be 25-30 pm/V at 633 nm wavelength. To prevent the orientational relaxation of poled polymer, the thermal crosslink reaction was induced using diisocyanate as a crosslinker between the side chains themselves. Temporal stabilities of second-order NLO coefficients of crosslinked polymer systems were proved much better than that of guest-host system or other side chain polymers. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of nonlinear optical side-chain polyimides containing the thiadiazole chromophores

Thermally stable second-order nonlinear optical (NLO) polyimides were synthesized using a standard condensation polymerization technique. The polyimides were prepared from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and pyromellitic dianhydride (PMDA) with two aromatic azo- and diazo-diamine derivatives as the NLO chromophores. The resulting polyimides were characterized by FTIR, ¹H-NMR, UV-vis spectroscopies, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The weight-average molecular weights of polyimides determined by gel permeation chromatography (GPC) were in the range of 32,100 to 39,300 (M_w/M_n = 1.58–1.74). All the polyimides exhibited an excellent solubility in many of the aprotic polar organic solvents, manifesting that these polyimides offer good processability. The glass transition temperature for the resulting polyimides was in the range of 152 to 194°C and most of them showed high thermal stability. Particularly, the polyimides containing diazo group and PMDA backbone showed an enhanced thermal stability and glass transition temperature. The second harmonic generation (SHG) coefficients (d₃₃) of the poled polyimide films range from 43.71 to 80.49 pm/V at 532 nm. Further, it is noticed that there was no SHG decay below 180°C because of the partial main-chain character of the polyimide structure, which is acceptable for nonlinear optical device applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Monohydroxy‐hydrazone‐functionalized thermally crosslinked polymers for nonlinear optics

The synthesis and properties of six hydrazone‐functionalized crosslinked polymers possessing stable nonlinear optics (NLO) properties are presented. First, a series of six hydroxy‐functionalized, NLO‐active hydrazone chromophores were synthesized. These chromophores were then grafted via its hydroxy functionality on an epoxy polymer to obtain the six NLO‐active soluble prepolymers. The grafting reaction yielded multiple secondary hydroxyl sites, which were used for further crosslinking by formulation of the prepolymer with a blocked polyisocyanate crosslinker. This formulation was spin‐coated on glass slides to form 2–2.5 μ thick defect‐free transparent films. The films were corona‐poled above their glass‐transition temperatures to align the chromophores in a noncentrosymmetric fashion and were simultaneously cured. The thermal characteristics of the second‐order nonlinearity of the six polymers were compared to illustrate the key structure–property relationships underlying the performance of the films in terms of NLO activity and thermal stability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 770–781, 2004     

Synthesis of novel polyimide with highly enhanced thermal stability of second harmonic generation for electro-optic applications

2,3-Bis-(3,4-dicarboxyphenylcarboxyethoxy)-1-(2,2-dicyanovinyl)benzene dianhydride (4) was prepared and reacted with 1,4-phenylenediamine to yield novel Y-type polyimide 5 containing 2,3-dioxybenzylidenemalononitrile group as NLO-chromophores, which constitute parts of the polymer backbones. The resulting polyimide 5 was soluble in polar solvents such as acetone and N,N-dimethylformamide. Polymer 5 showed a thermal stability up to 330 °C in thermogravimetric analysis thermogram with T _g value obtained from differential scanning calorimetry thermogram near 190 °C. The second harmonic generation (SHG) coefficient (d ₃₃) of poled polymer films at the 1064 nm fundamental wavelength was around 3.15×10^-9 esu. The dipole alignment exhibited a thermal stability even at 20 °C higher than the glass-transition temperature, and there was no SHG decay below 210 °C because of the partial main chain character of polymer structure, which was acceptable for nonlinear optical device applications.     

Preparation of novel polyimides with high thermal stability of dipole alignment for electro-optic applications

3,4-Bis-(3,4-dicarboxyphenylcarboxyethoxy)-1-(2,2-dicyanovinyl)benzene dianhydride (4) was prepared and reacted with 1,4-phenylenediamine and 4,4’-oxydianiline to yield novel Y-type polyimides 5-6 containing 3,4-dioxybenzylidenemalononitrile groups as NLO-chromophores, which constitute parts of the polymer backbones. The resulting polyimides 5-6 were soluble in polar solvents such as acetone and N,N-dimethylformamide. Polymers 5-6 showed a thermal stability up to 330 °C in thermogravimetric analysis thermograms with T _g values obtained from differential scanning calorimetry thermograms in the range of 181–190 °C. The second harmonic generation (SHG) coefficients (d ₃₃) of poled polymer films at the 1064 nm fundamental wavelength were around 4.73×10^-9 esu. The dipole alignment exhibited a thermal stability even at 20 °C higher than the glass-transition temperatures, there was no SHG decay below 200 °C because of the partial main chain character of polymer structure, which was acceptable for nonlinear optical device applications.     

New crosslinked polymer systems with high and stable optical nonlinearity

Thermo-crosslinkable copolymers (PGMAA and PGMAS) of glycidyl methacrylate containing azobenzene chromophores (20 mol%) and stilbene chromophores (19 mol%) respectively were synthesized and characterized. In order to obtain crosslinked polymers with high and stable second-order nonlinear optical (NLO) property, PGMAA and PGMAS were doped with a reactive nonlinear optical (NLO) dye, 4-nitro-4′-aminobiphenyl (20 mol% of the glydidyl group). In the poled state, these doped polymers systems (PGMAD and PGMSD) can be thermo-crosslinked to yield materials with high second-order (NLO) coefficient (d₃₃) of 4.33×10⁻⁷ esu and 4.74×10⁻⁷ esu respectively. The investigation of SHG decay at room temperature and 100°C showed that the polymer networks much improved the SHG stability.     

Synthesis and properties of novel X-type polyurethane containing dicyanovinylnitrocatechol of enhanced SHG thermal stability for electro-optic applications

Novel X-type polyurethane 5 containing 4-(2′,2′-dicyanovinyl)-5-nitrocatecholic groups as nonlinear optical chromophores, which constitute parts of the polymer backbone, was prepared and characterized. Polyurethane 5 is soluble in common organic solvents such as acetone and N,N-dimethylformamide. It shows thermal stability up to 270 °C from thermogravimetric analysis with a glass-transition temperature obtained from differential scanning calorimetry thermogram of around 113 °C. The second harmonic generation (SHG) coefficient (d ₃₃) of poled polymer film at 1,064 nm fundamental wavelength is around 5.72 × 10^?9 esu. The dipole alignment exhibits a thermal stability even at 7 °C higher than glass-transition temperature, and there was no SHG decay below 120 °C due to the partial main-chain character of the polymer structure, which is acceptable for nonlinear optical device applications.     

Thermally stable nanocrystallised mesoporous zirconia thin films

A supercritical fluid process method has been developed for fabricating mesoporous zirconia thin films with enhanced thermal stability up to a temperature of 850 °C. Both the supercritical CO₂ and the precursor tetramethoxysilane play an important role in enhancing the thermal stability of these films. Powder X-ray diffraction, Atomic force microscope, spectroscopic ellipsometry and transmission electron microscope analyses show that the thin films fabricated by the supercritical fluid process method have a highly ordered mesoporous structure, a nanocrystalline inorganic framework and a high optical transparency. These zirconia thin films have potential applications as electrodes in solid oxide fuel cells where high thermal stability is essential.     

Synthesis and thermal properties of polyurethane–polysiloxane crosslinked polymer networks

Polysiloxane–polyurethane crosslinked polymer networks (PSI–PU) were synthesized in solution by polymerization of oligosiloxanes containing γ‐hydroxy propyl groups with polymethane polyphenyl polyisocyanate. Polyether‐based polyurethane and polyester‐based polyurethane were also prepared by a “one‐shot” method. Their thermal properties were studied by thermogravimetric analysis. It was observed that the thermal stability of PSI–PU was better than that of polyether‐based polyurethane and polyester‐based polyurethane, and an inert atmosphere had no effect on decomposition of polyurethanes below 350°C. It was found that polyurethane–polysiloxane crosslinked polymer networks decomposed slower in oxygen than in nitrogen in the temperature range of 350–550°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 310–315, 2003     

Characterization of thermally crosslinkable polyester films by thermomechanical analysis: a versatile and very sensitive technique for the evaluation of low crosslinking degree in polymers

Thermomechanical analysis (TMA) is an effective technique for the characterization of small samples such as thin films of micrometric thickness, allowing the determination of thermal events such as glass transition, softening temperature and thermal expansion. Here we describe use of the TMA technique to investigate the drying and curing properties of polyester thin films ranging from 40 to 70 μm thick. The main purpose of this study was to investigate the effects of residual solvent and crosslinking on the glass transition and softening temperatures of the polyester films subjected to thermal cycling. Despite the fact that the analysed films were thinner than 100 μm, TMA proved to be very sensitive to small changes in residual solvent content and to the effects of the degree of crosslinking on the glass transition and softening temperatures of the polymer films. The most important finding is the possibility of detecting very small degrees of crosslinking in an easy, fast and quantitative way. Other methods such as swelling were not sensitive enough to differentiate the crosslinked samples and data for thicker films are not comparable to the data for thin films. © 2018 Society of Chemical Industry