Synthesis and characterization of Y‐type polymers for second‐order nonlinear optical applications

A series of dicyanomethylene‐substituted polymers having Y‐type molecular architecture were synthesized by Knoevenagel condensation reaction. The polymers were found to be soluble in organic solvents like tetrahydrofuran and chloroform. From gel permeation chromatography, the molecular weights of the polymers were found to be in the range of 15,300–33,800 g/mol. Thermal analysis showed that the polymers were stable up to 350 °C with glass transition temperature (T_g) in the range of 129–212 °C. These polymers were found to form good optical quality films. The order parameter was calculated to be in the range of 0.01–0.48. Atomic force microscopy indicated prominent morphology changes due to alignment of dipoles after poling. By using Nd:YAG laser of 1064 nm, angular dependence and temperature dependence of second‐harmonic generation intensity were investigated. The geometry optimization, shape of polymers, and restricted torsion angle between acceptor and donor substituents (push–pull system) were calculated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Characterization of a side chain polymer for second‐order nonlinear optical properties

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 d₃₃ 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. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1245–1254, 1999     

New PVK‐based nonlinear optical polymers: Enhanced nonlinearity and improved transparency

A series of poly(vinylcarbazole)‐based polymers containing sulfonyl‐based nonlinear optical chromophores as the side chains were prepared conveniently through a postfunctionalization approach. In the polymers, the subtle structure of the chromophore moieties could be easily modified by the introduction of different isolation group, to adjust the property of the resultant polymers. The polymers exhibited good optical transparency, besides their good processability and thermal stability. The poled polymer films exhibited large second harmonic generation (SHG) coefficients of d₃₃ values (up to 28.6 pm/V) with excellent thermal stability (about 90% of the maximal SHG coefficients remain at ～ 110 °C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2983–2993, 2008     

Synthesis and characterization of azo–bisbenzylidene‐based polymers for second order nonlinear optics

Main chain polymers containing azo and bisbenzylidene moiety were synthesized by polycondensation method. The successful polymerization reaction was characterized by UV–vis absorption, FT‐IR and NMR spectroscopy. The resulting polymers were soluble in polar solvents like dimethyl formamide (DMF) and showed good thermal stability up to 250 °C. These polymers were blended with poly methyl methacrylate (PMMA) and corona poled for characterizing second harmonic generation (SHG) property. Temperature stability study of SHG intensity of poled polymer showed that it is stable up to 80 °C. To improve temperature stability further the crosslinking of polymer under UV light is proposed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4317–4324     

Synthesis and polymerization of N‐(4‐tetrahydropyranyl‐oxyphenyl)maleimide

N‐(4‐Tetrahydropyranyl‐oxy‐phenyl)maleimide (THPMI) was prepared and polymerized by radical or anionic initiators. THPMI could be polymerized by 2,2′‐azobis(isobutyronitrile) (AIBN) and potassium tert‐butoxide. Radical polymers (poly(THPMI)r) were obtained in 15–50% yields for AIBN in THF at 65°C after 2–5 h. The yield of anionic polymers (poly(THPMI)a) obtained from potassium tert‐butoxide in THF at 0°C after 20 h was 91%. The molecular weights of poly(THPMI)r and poly(THPMI)a were M_n = 2750–3300 (M_w/M_n = 1.2–3.3) and M_n = 11300 (M_w/M_n = 6.0), respectively. The difference in molecular weights of the polymers was due to the differences in the termination mechanism of polymerization and the solubility of these polymers in THF. The thermal decomposition temperatures were 205 and 365°C. The first decomposition step was based on elimination of the tetrahydropyranyl group from the poly(THPMI). Positive image patterns were obtained by chemical amplification of positive photoresist composed of poly(THPMI) and 4‐morpholinophenyl diazonium trifluoromethanesulfonate used as an acid generator. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 341–347, 1999     

Effect of pressure and temperature on chromophore reorientation in a new syndioregic main‐chain hydrazone nonlinear optical polymer

Second harmonic generation (SHG) was used to measure the temperature dependence of the reorientation activation volume (ΔV*) of a syndioregic main‐chain hydrazone (SMCH) nonlinear optical polymer. The decay of the SHG signal from poled films of SMCH was recorded at hydrostatic pressures up to 2924 atm and at temperatures between 25 °C below the glass‐transition temperature (T_g) to 20 °C above it. ΔV* for pressures less than 500–1000 atm and T > T_g decreased as the temperature was increased. For pressures greater than 1000 atm, ΔV* was essentially constant for all temperatures. In addition, the size of ΔV* indicated that the chromophore in this main chain was internally flexible. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 895–900, 2001     

Synthesis and properties of conjugated polymers containing 3,9‐carbazolylene and silylenevinylene moieties in the main chain

Novel conjugated polymers containing 3,9‐carbazolylene and silylenevinylene moieties were synthesized by the hydrosilylation polymerization of 1,4‐bis(3‐ethynyl‐9‐carbazolyl)benzene ( 1 ) with various bis(hydrosilane)s or dihydrosilanes using a rhodium catalyst. Polymers with weight‐average molecular weights ranging from 5400 to 20,000 were obtained in 55–97% yields by the polyaddition with a rhodium catalyst in toluene at 25 °C for 24 h. All the polymers were soluble in CHCl₃ and THF, and had predominantly trans‐structures. The polymers exhibited λ_max at a longer wavelength region than 1 , and emitted fluorescence in 14–50% quantumn yields. The polymers were oxidized and reduced in the region of 0.4–1.6 V, and thermally stable up to 200 °C under air. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1815–1821, 2010     

Synthesis and properties of novel Y‐type nonlinear optical polyimides with high thermal stability of second harmonic generation

2,4‐Bis‐(3,4‐dicarboxyphenylcarboxyethoxy)‐1‐(2,2‐dicyanovinyl)benzene dianhydride (4) was prepared and reacted with 4,4′‐oxydianiline, 4,4′‐diaminobenzanilide and 4,4′‐(hexafluoroisopropylidene)dianiline to yield novel Y‐type polyimides 5‐7 containing 2,4‐dioxybenzylidenemalononitrile groups as nonlinear optical (NLO) chromophores, which constitute parts of the polymer backbone. The resulting polyimides 5‐7 are soluble in polar solvents such as dimethylsulfoxide and N,N‐dimethylformamide. Polymers 5‐7 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 179–194 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at the 1064 nm fundamental wavelength were around 5.56 × 10^?9 esu. The dipole alignment exhibited exceptionally high thermal stability even at 20 °C higher than the glass‐transition temperature there was no SHG decay below 215 °C because of the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3078–3087, 2008     

Thermally stable nonlinear optical polyurea functionalized by multiple charge‐transfer chromophore

A novel high glass‐transition temperature (272 °C) polyurea functionalized by a multiple charge‐transfer chromophore, 2‐{4‐[4,5‐bis(4‐nitrophenyl)imidazolyl]phenyl}‐4,5‐bis(4‐aminophenyl)imidazole, was synthesized. Simultaneous poling and polymerization and the in situ second‐harmonic generation (SHG) measurement technique was carried out to evaluate the thermal stability of the poling‐induced orientation. The nonlinear optical coefficient d₃₃ of poled polyurea film was 24 pm/V at 1064 nm fundamental wavelength. The SHG signal of the poled polymer film was quite stable below 200 °C and still remained 80% of its initial value after heating at 250 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4297–4301, 2002     

Synthesis and electro‐optic properties of novel X‐type polyurethane containing nitrophenylazonitroresorcinoxy group with highly enhanced thermal stability of dipole alignment

Novel X‐type polyurethane 4 containing 4‐(4‐nitrophenylazo)‐6‐nitroresorcinoxy 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 acetone and N,N‐dimethylformamide. It shows thermal stabilities up to 270 °C from thermogravimetric analysis with glass transition temperature obtained from differential scanning calorimetry of about 134 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at 1064 nm fundamental wavelength is 5.37 × 10^?9 esu. Polymer 4 exhibits a thermal stability up to T_g, and no significant SHG decay is observed below 135 °C, which is acceptable for NLO device applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 760–766     

Synthesis and optical properties of novel blue‐light‐emitting poly(p‐phenylene vinylene) derivatives with pendant oxadiazole or cyano groups

Two novel poly(p‐phenylene vinylene) polymers, which carried side substituents with cyano groups or 1,3,4‐oxadiazole, were synthesized by Heck coupling. They consisted of alternating conjugated segments and nonconjugated aliphatic spacers. The polymers had moderate molecular weights, were amorphous, and dissolved readily in tetrahydrofuran and halogenated organic solvents. They were stable up to approximately 340 °C in N₂ and 290 °C in air, and the anaerobic char yield was around 60% at 800 °C. The polymer with cyano side groups emitted blue light in solutions and thin films with identical photoluminescence (PL) maximum at 450 nm; this supported the idea that chain interactions were hindered even in the solid state. The PL maximum of this polymer in thin films was blueshifted upon annealing at 120 °C, indicating a thermochromic effect as a result of conformational changes in the polymer backbone. The polymer containing side substituents with oxadiazole rings emitted blue light in solutions with a PL maximum at 474 nm and blue‐greenish light in thin films with a PL maximum at 511 nm. The PL quantum yields of the polymers in tetrahydrofuran were 0.13–0.24. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1768–1778, 2004     

The design,synthesis, and nonlinear optical properties of novel X‐type polyurethane containing dicyanovinylnitroresorcinoxy group with enhanced SHG thermal stability

Novel X‐type polyurethane 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. Polyurethane 5 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It shows thermal stability up to 280 °C from thermogravimetric analysis with a glass transition temperature (T_g) obtained from differential scanning calorimetry thermogram of around 120 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at 1064‐nm fundamental wavelength is around 6.12 × 10^?9 esu. The dipole alignment exhibits a thermal stability even at 5 °C higher than T_g, and there was no SHG decay below 125 °C due to the partial main chain character of the polymer structure, which is acceptable for NLO device applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Molecular design,synthesis, and nonlinear optical properties of novel T‐type polyimides with exceptionally high thermal stability of the second harmonic generation

2,5‐Bis‐(3,4‐dicarboxyphenylcarboxyethoxy)‐4′‐nitrostilbene dianhydride was prepared and reacted with 1,4‐phenylenediamine, 4,4′‐oxydianiline, 4,4′‐diaminobenzanilide, and 4,4′‐(hexafluoroisopropylidene)dianiline to yield unprecedented novel T‐type polyimides ( 4 – 7 ) containing 2,5‐dioxynitrostilbenyl groups as nonlinear optical chromophores, which constituted parts of the polymer backbones. 4 – 7 were soluble in polar solvents such as acetone and N,N‐dimethylformamide. They showed thermal stability up to 300 °C in thermogravimetric analysis thermograms; the glass‐transition temperatures obtained from differential scanning calorimetry thermograms were around 153 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at the 1064‐cm^?1 fundamental wavelength were around 4.35 × 10^?9 esu. The dipole alignment exhibited exceptionally high thermal stability even at 45 °C higher than the glass‐transition temperature, and there was no SHG decay below 200 °C because of the partial main‐chain character of the polymer structure, which was acceptable for nonlinear optical device applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3189–3199, 2004     

Synthesis and characterization of new soluble poly(amide‐imide)s derived from 2,2‐bis[4‐(4‐trimellitimidophenoxy)phenyl]hexafluoropropane

A series of new soluble poly(amide‐imide)s were prepared from the diimide‐dicarboxylic acid 2,2‐bis[4‐(4‐trimellitimidophenoxy)phenyl]hexafluoropropane with various diamines by direct polycondensation in N‐methyl‐2‐pyrrolidinone containing CaCl₂ with triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.52–0.86 dL · g^?1. The poly(amide‐imide)s showed an amorphous nature and were readily soluble in various solvents, such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, pyridine, and cyclohexanone. Tough and flexible films were obtained through casting from DMAc solutions. These polymer films had tensile strengths of 71–107 MPa and a tensile modulus range of 1.6–2.7 GPa. The glass‐transition temperatures of the polymers were determined by a differential scanning calorimetry method, and they ranged from 242 to 279 °C. These polymers were fairly stable up to a temperature around or above 400 °C, and they lost 10% of their weight from 480 to 536 °C and 486 to 537 °C in nitrogen and air, respectively. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3498–3504, 2001     

Rigid‐rod polyamides and polyimides prepared from 4,3″‐diamino‐2′,6′‐di(2‐naphthyl)‐p‐terphenyl and 2′,6′,3‴,5‴‐tetra(2‐naphthyl)‐4,4″‐diamino‐p‐quinquephenyl

A series of rigid‐rod polyamides and polyimides containing p‐terphenyl or p‐quinquephenyl moieties in backbone as well as naphthyl pendent groups were synthesized from two new aromatic diamines. The polymers were characterized by inherent viscosity, elemental analysis, FT‐IR, ¹H‐NMR, ¹³C‐NMR, X‐ray, differential scanning calorimetry (DSC), thermomechanical analysis (TMA), thermal gravimetric analysis (TGA), isothermal gravimetric analysis, and moisture absorption. All polymers were amorphous and displayed T_g values at 304–337°C. Polyamides dissolved upon heating in polar aprotic solvents containing LiCl as well as CCl₃COOH, whereas polyimides were partially soluble in these solvents. No weight loss was observed up to 377–422°C in N₂ and 355–397°C in air. The anaerobic char yields were 57–69% at 800°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 15–24, 1999     

Effect of pressure and temperature on chromophore reorientation in a side-chain nonlinear optical polymer

Second harmonic generation (SHG) was used to measure the temperature dependence of the reorientation activation volume of the side-chain copolymer poly(disperse red 1 methacrylate-co-methyl methacrylate) (DR1-MMA). The decay of the SHG signal from poled films of DR1-MMA was recorded at hydrostatic pressures up to 3060 atm and at different temperatures between 25°C below the glass transition temperature (T_g) to 35°C above it. The activation volume, ΔV^*, decreased with increasing temperature. The data suggests that the coupling between chromophore reorientation and the long-range motion of the polymer is stronger for the DR1-MMA side-chain system than in previously measured guest–host systems. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2793–2803, 1998     

Synthesis and characterization of highly fluorinated poly(phthalazinone ether)s based on AB‐type monomers

Four different fluorinated methyl‐ and phenyl‐substituted 4‐(4‐hydroxyphenyl)‐2‐(pentafluorophenyl)‐phthalazin‐1(2H)‐ones, AB‐type phthalazinone monomers, have been successfully synthesized by nucleophilic addition–elimination reactions of methyl‐ and phenyl‐substituted 2‐((4‐hydroxy)benzoyl)benzoic acid with 1‐(pentafluorophenyl)hydrazine. Under mild reaction conditions, the AB‐type monomers underwent self‐condensation polymerization reactions successfully and gave fluorinated poly(phthalazinone ether)s with high molecular weights. Detailed structural characterization of the AB‐type monomers and fluorinated polymers was determined by ¹H NMR, ¹⁹F NMR, FTIR, and GPC. The solubility, thermal properties, mechanical properties, water contact angles, and optical absorption of the polymers were evaluated. The polymers had high T_gs varying from 337 to 349 °C and decomposition temperatures (T_{d, 25} wt %) above 409 °C. Tough, flexible films were cast from THF and chloroform solutions. The films showed excellent tensile strengths ranging from 70 to 85 MPa with good hydrophobicities with water contact angles higher than 95.5 °C. The polymers had absorption edges below 340 nm and very low absorbance per cm at higher wavelengths 500–2500 nm. These results indicate that the polymers are promising as high performance materials, for example, membranes and hydrophobic materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1761–1770     

Sterically encumbered poly(arylene ether)s containing spiro‐annulated substituents: Synthesis and thermal properties

Four novel 2‐trifluoromethyl‐activated bisfluoro monomers have been synthesized successfully using a Suzuki‐coupling reaction of 3‐trifluoromethyl‐4‐fluoro phenyl boronic acid with 2,7‐dibromofluorene with varied pendants. Four monomers were converted to a series of fluorene‐based poly(arylene ether)s with pendants by nucleophilic displacement of the fluorine atoms on the terminal benzene ring with 4,4′‐hexafluoroisopropylidenediphenol. The polymers obtained by displacement of the fluorine atoms, exhibit weight‐average molecular weight up to 9.89 × 10⁴ g/mol in GPC. Thermal analysis studies indicated that these polymers did not show melting endotherms but did show relatively high T_g values up to 270 °C in DSC and outstanding thermal stability up to 532 °C for 5% weight loss in TGA in a nitrogen atmosphere. The polymers are soluble in a wide range of organic solvents: THF, CHCl₃, NMP, DMAc, DMF, toluene and EAc, and so forth, at room temperature. Transparent and flexible films were easily prepared by solution casting from chloroform solution of each of the polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Novel blue‐greenish electroluminescent poly(fluorenevinylene‐alt‐dibenzothiophenevinylene)s and their model compounds

Poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐2,8‐vinylene) (PS) and poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐5,5‐dioxide‐2,8‐ vinylene) (PSO) as well as corresponding model compounds were synthesized by Heck coupling. Both the polymers and model compounds were readily soluble in common organic solvents such as tetrahydrofuran, dichloromethane, chloroform, and toluene. The polymers showed a decomposition temperature at ～430 °C and a char yield of about 65% at 800 °C in N₂. The glass‐transition temperatures of the polymers were almost identical (75–77 °C) and higher than those of the model compounds (26–45 °C). All samples absorbed around 390 nm, and their optical band gaps were 2.69–2.85 eV. They behaved as blue‐greenish light emitting materials in both solutions and thin films, with photoluminescence emission maxima at 450–483 nm and photoluminescence quantum yields of 0.52–0.72 in solution. Organic light‐emitting diodes with an indium tin oxide/poly(ethylene dioxythiophene):poly(styrene sulfonic acid)/polymer/Mg:Ag/Ag configuration with polymers PS and PSO as emitting layers showed green electroluminescence with maxima at 530 and 540 nm, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6790–6800, 2006     

Phase separation of polymer‐functionalized SWNTs within a PMMA/polystyrene blend

Phase separation of polystyrene (PS) and poly(methyl methacrylate) (PMMA) blends was used as a means to segregate PS‐ or PMMA‐functionalized single‐walled carbon nanotubes (SWNTs) in thin films. Dilute solutions (5 wt % in THF) of 1:1 PS/PMMA blends containing the functionalized nanotubes were spin cast and annealed at 180 °C for 12 h. Two different polymer molecular weights were used (M_n = 8000 or M_n = 22,000), and were of approximately equivalent molecular weight to those attached to the surface of the nanotubes. Nanotube functionalization was accomplished using the Cu(I)‐catalyzed [3 + 2] Huisgen cycloaddition, in which alkyne‐decorated nanotubes were coupled with azide‐terminated polymers, resulting in polymer‐SWNT conjugates that were soluble in THF. Characterization of the annealed films by scanning Raman spectroscopy, which utilized the unique Raman fingerprint of carbon nanotubes, enabled accurate mapping of the functionalized SWNTs within the films relative to the two phase‐separated polymers. It was found that nanotube localization within the phase‐separated polymer films was influenced by the type of polymer attached to the nanotube surface, as well as its molecular weight. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 450–458, 2009