Synthesis and Characterization of Novel Second-Order Nonlinear Optical Chromophore with Multi-Hydroxyl Groups Donor

New electro optical chromophore with 4-(bis(2-hydroxyethyl)amino)-2,6-dipropoxybenzaldehyde as electron donor was synthesized and characterized by ¹H NMR spectra and mass spectra. Four hydroxyl groups were introduced to the electron donor, which could be easily reacting with carboxyl, isocyanate, anhydride, and so on, to afford us second-order nonlinear optical polymers. Chromophore T showed us good solubility in common solvents, thermal stability (above 200°C) and expected Uv-vis absorption. In this article, polymethyl methacrylate (PMMA) doped with chromophore T at different loading density was prepared to second- order nonlinear optical films by spin coating. These films showed us large second-order nonlinear optical coefficients, 13.5, 19.7, 24.3, and 26.4 pm/V for the second-order nonlinear optical films with chromophore loading density of 10 wt%, 20 wt%, 30 wt%, and 40 wt%, respectively.     

Novel, side-on, PVK-based nonlinear optical polymers: Synthesis and NLO properties

A novel, poly(vinylcarbazole)-based nonlinear optical polymer (side-on type), in which the chromophore was attached to the polymer backbone at the centre of the D-π-A bridge, was synthesized conveniently via the post-Knoevenagel condensation reaction. The structure of chromophore was further modified by the introduction of an isolation spacer (carbazole group) to improve poling efficiency. The ensuing polymer displayed good solubility and high thermal stability and its poled film exhibited a relatively large d₃₃ value of ≤56.0 pm/V.     

Thermally stable nonlinear optical polyimide functionalized by N,N‐diallylamino‐substituted chromophore

Thermally stable nonlinear optical (NLO) polyimide prepolymers with different chromophore‐loading levels were prepared through an addition reaction of bismaleimide 1 and N,N‐diallylamino‐substituted chromophore 2. The prepolymers were used to prepare NLO polyimide in a simultaneously poling/curing process. These prepolymers exhibited excellent film‐forming quality and good solubility in low boiling‐point solvents. Kinetic parameters (n, ln A,Ea) of their solidification reaction were determined by the dynamic method. Thermal and NLO properties of the cured polyimides with various chromophore‐loading levels were studied. With increase of the chromophore‐loading level, the glass transition temperature (T_g) and the thermal stability of the polyimides decreased, but the second‐order nonlinearity of the poled film increased. The largest d₃₃ coefficient obtained was 76.2 pm/V at 1064 nm. The SHG signal was rather stable up to 120°C. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2939–2947, 2000     

Use of FTIR combined with forms of water to study the changes in hydrogen bonds during low-temperature heating of lignite

The changes in the hydrogen bonds (HBs) of three types of Indonesian lignite during low-temperature heating were investigated. The amount of water loss was determined by weighing the samples before and after heating in an oven. The changes in the number of the different types of HBs were determined using Fourier transform infrared spectroscopy coupled with types of water in lignite. The number of peak positions and absorption bands in each spectrum was determined by curve-fitting analysis with a Gaussian function. The quantified integrated area of aromatic hydrogen atoms was used to accurately investigate the changes in the HBs. The results show that at low temperatures (T ≤ 50°C), free water is mainly removed, and the HBs broken are those between free water molecules. However, at medium temperatures (50 <T ≤ 100°C), bound water is mainly removed. The number of HBs significantly changes because of the breaking of bound water molecule HBs and bound water cluster–carboxyl group HBs, and the formation of nonfreezable moisture HBs. At high temperatures (100 <T < 125°C), nonfreezable moisture can be released. The number of HBs changes as a result of competition between the removal of nonfreezable moisture and the increase in the number of carboxyl groups. At higher temperatures (T ≥ 125°C), the moisture remaining in lignite is thermal decomposition moisture. In addition, the rate of decomposition of carboxyl groups is higher than the rate of generation, which means that the number of HBs markedly decreases at higher temperatures.     

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.     

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 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.     

A glutamic acid-based polymer keeping intact the integrity of all the three original functionalities of the amino acid

Dimethyl glutamate, on treatment with allyl bromide, afforded dimethyl N,N-diallylglutamate which upon alkaline ester hydrolysis followed by acidification with aqueous HCl gave N,N-diallylglutamic acid hydrochloride [(CH₂=CH–CH₂)₂NH⁺CH(CO₂H)(CH₂)₂CO₂H Cl^?] I. Using Butler’s cyclopolymerization protocol, new monomer I underwent ammonium persulfate-initiated polymerization to give pyrrolidine ring-embedded linear cyclopolymer II i.e. ?[?CH₂(C₄H₆)NH⁺{CH(CO₂H)(CH₂)₂CO₂H Cl^?}CH₂?]?_n retaining the integrity of all the three functionalities of glutamic acid. Under the influence of pH, the repeating units of triprotic acid (+) in II were equilibrated to those of water-insoluble diprotic polyzwitterionic acid (±) III, water-soluble monoprotic poly(zwitterion-anion) (±?) IV, and its conjugate base polydianion (=) V. The critical salt concentration required to promote water solubility of (±) III has been determined to be 0.548 M NaCl, 0.271 M NaBr, 0.133 M NaI. The basicity constants of the carboxyl groups and trivalent nitrogen in (=) V have been determined. A 5 ppm and 20 ppm concentrations of III are effective in inhibiting the precipitation of CaSO₄ from its supersaturated solution with a ≈100% scale inhibition efficiency at 40 °C for a duration of over 3 and 16 h, respectively.     

Synthesis of Novel D-Pi-A Chromophore with Two Hydroxyl Groups in Electron Donor

New electro optical chromophore with 4-(diethylamino)-2,6-bis((6-hydroxyhexyl)oxy)benzaldehyde as electron donor was synthesized and characterized by ¹H NMR spectra and mass spectra. Two long branches were introduced to the electron donor to reduce the interaction among the chromophores and improve the chromophores’ solubility. Hydroxyl groups were introduced to branches’ end, which could be easily reacted with isocyanate affording us polyurethane. In this article, novel polyurethane with this new chromophore as side chains was prepared and used as thermo optical films by spin coating. These films showed us low optical absorption at communication wavelength, good thermal stability and large thermo-optics coefficients.     

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.     

Effects of hydrophobic chain length on temperature dependence of monolayer behavior of ester-type tartaric geminis

Ester-type tartaric gemini amphiphiles bearing two carboxyl groups and two hydrophobic alkanoyl groups were prepared from L-tartaric acid, and the pressure-area (π-A) isotherms for a series of symmetric tartaric gemini amphiphiles were measured by the conventional film-balance technique. The effects of the length of the hydrophobic alkanoyl chains and of the subphase temperature (T(sub)) on the π-A isotherms for these compounds were examined. As the length of the hydrophobic alkyl chain increased, a more tightly packed monolayer was formed at the air-water interface. The melting temperature (T(m)) of the monolayer on the water surface was evaluated from the subphase temperature (T(sub)) dependence of the monolayer static elasticity ε(s), based on a π-A isotherm. A clear relationship between T(m) and hydrophobic carbon number (n) was observed for 2D monolayers of tartaric geminis on water surfaces, as well as for fatty acids and/or 3D solids.     

Changes of oxygen-containing groups during thermal treatment and their influences on moisture readsorption of lignite

The changes in oxygen-containing groups in the thermal treatment process of lignite were analyzed and the moisture readsorption amounts of upgraded coals were related in this study. A chemical titration method was applied to determine the types and contents of oxygen-containing groups in raw lignite and upgraded coals obtained in the temperature range of 353–633 K under atmospheres of argon, air, and carbon dioxide. Experimental results showed that the oxygen-containing groups mainly involved carbonyl, phenolic hydroxyl, and carboxylic groups (including carboxyl and carboxylate), among which phenolic groups were dominant. These different oxygen-containing groups decomposed discriminatingly with temperature according to thermal stability. The removal of oxygen-containing groups proceeded more easily in a CO₂ atmosphere compared to in Ar. The oxidation reaction occurring on the surface of lignite exposed to air led to an increase in oxygen-containing groups. The different types of oxygen-containing groups possessed various combining abilities with water, among which carboxyl was considered the most important group for the moisture readsorption. Decomposition of oxygen-containing groups in the thermal treatment process of lignite mainly caused a reduction in monolayer water adsorption and further decreased the multilayer water.     

Enhanced solubility of novel poly(benzoxazole)s with a soft linkage and a rigid pendant group

Aromatic poly(benzoxazole)s are a class of rigid‐rod conjugated polymers. However, their poor solubility in organic solvents limits potential applications. Thus, a good method that can address this dilemma is needed, given that existing methods involve models with either poor solubility but good thermal stability or good solubility but poor thermal stability. In this paper we report a novel aromatic poly(benzoxazole) with a soft linkage and a rigid pendant group. Structural characterizations of the polymers via Fourier transform infrared and proton nuclear magnetic resonance spectroscopy reveal the formation of a benzoxazole ring and an imide ring. The introduction of rigid pendant groups improved the solubility and enhanced the thermal stability of the polymer, which was impaired by the incorporation of the soft linkage. Most of these polymers are soluble at room temperature or when heated in dimethyl sulfoxide, N,N‐dimethylformamide or N,N‐dimethylacetamide. Some polymers can even be dissolved in m‐cresol and tetrahydrofuran. A 10% weight loss in these polymers was observed at temperatures over 410 °C. Moreover, the incorporation of the imide pendant group increased the conjugation length of the polymer structural unit and accelerated electron delocalization. Copyright © 2012 Society of Chemical Industry     

Synthesis and properties of sulfonated poly(arylene ether nitrile) copolymers containing carboxyl groups for proton‐exchange membrane materials

A series of sulfonated poly(arylene ether nitrile) copolymers containing carboxyl groups were synthesized via a nucleophilic aromatic substitution reaction from phenolphthalein, hydroquinone sulfonic acid potassium salt, and 2,6‐difluorobenzonitrile in N‐methyl pyrrolidone (NMP) with K₂CO₃ as a catalyst. The synthesized copolymers had good solubility in common polar organic solvents and could be easily processed into membranes from solutions of dimethyl sulfoxide, NMP, N,N′‐dimethyl acetylamide, and dimethylformamide. Typical membranes in acid form were gained, and the chemical structures of these membranes were characterized by Fourier transform infrared analysis. The thermal properties, fluorescence properties, water uptake, ion‐exchange capacity, and proton conductivities of these copolymers were also investigated. The results indicate that they had high glass‐transition temperatures in the range 151–187°C and good thermal stability, with the 10 wt% loss temperatures ranging from 330 to 351°C under nitrogen. The copolymers showed characteristic unimodal ultraviolet–visible (UV–vis) absorption and fluorescence emission, and the UV–vis absorption, fluorescence excitation, and emission peaks of the copolymers were obvious. Moreover, the copolymer membranes showed good water uptake and proton conductivities at room temperature and 55% relative humidity because of the introduction of both sulfonic acid groups and carboxyl groups into the copolymers, whose contents were in ranges 18.45–67.86 and 3.4 × 10^?4 to 3.0 × 10^?3 s/cm, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40213.     

Fluorene‐based click polymers: Relationship between molecular structure and nonlinear optical properties

To further understand the relationship between the polymer structure and nonlinear optical (NLO) property, in this article, three fluorene‐based triazole functional polymers with different linked chains were designed and controllably prepared by click chemistry method. The structures and properties of these polymers were characterized and evaluated with Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, ultraviolet spectroscopy, fluorescence spectra, dynamic state laser light scattering, thermogravimetric analysis, and NLO analyses. The results exhibited that the target polymers displayed good solubility, high thermal stability, and well NLO properties. The relationships between molecular structures and optical properties were investigated by both theoretical simulation and experimental results. It was found that the rigid conjugated linked chain between triazole and chromophore can effectively enhance the NLO properties of the resultant polymers. The suitable rigid and flexible groups in the triazole polymers will result in good thermal stabilities. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40878.     

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.     

Bond strength of veneering porcelain to zirconia after different surface treatments

Aim: The aim of this study was to evaluate the effect of various surface treatments on the bond strength of veneering feldspathic porcelain to zirconia. Methods: Fifty yttria-stabilized tetragonal zirconia polycrystalline specimens were divided into five groups (n = 10) according to various surface treatments. The groups were as follows: Group 1: control group with liner application and no further surface treatment; Group 2: air-particle abrasion with 110 μm of alumina (Al₂O₃) particles; Group 3: grinding with a diamond disk; Group 4: Nd:YAG laser irradiation (the laser and the energy parameters were 10 Hz, and 2 W and 200 mJ, and the pulse duration (short pulse) range was up to 180 μs); Group 5: selective infiltration etching (SIE). After surface treatments, a liner application was performed for all surfaces according to the manufacturer’s instructions. Veneering porcelain was applied on zirconia surfaces using a Teflon mold. Shear bond strength was tested using a universal testing machine. The fractured surface morphologies were examined with scanning electron microscopy. The data were statistically analyzed using Mann–Whitney U and Kruskal–Wallis tests (α = .05). Results: The Megapascal values of the bonding groups were as follows: G1 = 8.62 ± 1.12, G2 = 13.87 ± 5.08, G3 = 12.31 ± 3.35, G4 = 17.32 ± 6.16, and G5 = 16.17 ± 4.55. Statistically significant differences were observed between the control group and the other groups (p < 0.05). Group 4 had the highest bond strength while G1 showed the lowest bond strength. No significant differences were found between the Nd:YAG, grinding, sandblasting, and SIE groups. Conclusion: Surface treatments had different effects on the shear bond strength of feldspathic porcelain to zirconia. Surface treatment techniques used in this study can be used on zirconia specimens prior to liner application to obtain an acceptable bond strength of veneering porcelain to zirconia. The effect of Nd:YAG laser irradiation and SIE techniques on bond strength of veneering ceramic to zirconia should be evaluated with further studies.     

Preparation of polystyrene/poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylenevinylene] fluorescent microspheres by miniemulsion polymerization

Fluorescent microspheres have great potential for use as probes in biological diagnostics. In this context, poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylenevinylene] (MEH‐PPV), a conjugated polymer which has high quantum yield, controllable emitting wavelength and facile processing in manufacture, was used as a fluorescent material for the preparation of polystyrene (PS)/MEH‐PPV fluorescent microspheres via miniemulsion polymerization. We demonstrate that the emitting wavelength of the PS/MEH‐PPV fluorescent microspheres can be regulated by changing the amount of azobisisobutyronitrile initiator in the polymerization process. Using acrylic acid comonomer, poly[styrene‐co‐(acrylic acid)]/MEH‐PPV fluorescent microspheres with functional carboxyl groups were also prepared. All the microspheres were characterized using transmission electron microscopy, scanning electron microscopy, fluorescence microscopy and fluorescence spectrophotometry. The functional carboxyl groups were characterized using Fourier transform infrared spectroscopy. This work provides a novel platform for the preparation of conjugated polymer fluorescent microspheres for biological applications. © 2012 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     

Comparative evaluation of push-out bond strength of Neo MTA Plus with Biodentine and white ProRoot MTA

Objective: The aim of this in vitro study was to evaluate the bond strength of a new calcium silicate cement, Neo MTA Plus (Avalon Biomed Inc. Bradenton, FL, U.S.A) by comparing ProRoot MTA and Biodentine.

Material and Methods: Sixty dentin slices were instrumented to achieve a diameter of 1.3 mm. Group 1: white ProRoot MTA, group 2: Biodentine, group 3: Neo MTA Plus – G (powder mixed with gel), group 4: Neo MTA Plus – W (powder mixed with distilled water) were loaded into cavities. The push-out bond strength values were measured. Data were analyzed using Welch ANOVA with Bonferroni correction p = 0.05. Failure modes (adhesive, cohesive, and mixture) were analyzed.

Results: The highest bond strength value was recorded in Neo MTA Plus mixed with gel (5.23 ± 1.78 MPa), whereas white ProRoot MTA (2.57 ± 0.66 MPa) had the lowest. Bond strength values of Neo MTA Plus mixed either with gel or with distilled water were statistically different from both white ProRoot MTA and Biodentine (2.61 ± 0.70 MPa) (p < 0.05). Adhesive failure was predominantly observed in all groups.

Conclusion: Neo MTA Plus could be considered as alternatives to the ProRoot MTA and Biodentine due to its better performance in bonding to root dentin.