The synthesis and characterization of heterocyclic azo dyes derived from 5-N,N-dialkylamino-2,2′-bithiophene couplers

Heterocyclic azo dyes were synthesized by diazotation of several substituted anilines and coupling with 5-N,N-dialkylamino-2,2′-bithiophenes to give 4-phenylazo-5-N,N-dialkylamino-2,2′-bithiophenes. This reaction contrasts with the behavior of 5-alkoxy-2,2′-bithiophenes towards aryldiazonium salts which provides 5-phenylazo-5-alkoxy-2,2′-bithiophenes. The thermal stability of the derivatives was evaluated using thermogravimetric analysis and their solvatochromic behaviour was investigated in several solvents of different polarity. The experimental results indicate that the heterocyclic azo dyes could be used as thermally stable, solvatochromic probes.     

Push–pull bithiophene azo-chromophores bearing thiazole and benzothiazole acceptor moieties: Synthesis and evaluation of their redox and nonlinear optical properties

Three series of bithiophene azo dyes functionalized with thiazol-2-yl or benzothiazol-2-yl-diazene acceptor moieties were synthesized through azo coupling reaction using 2,2′-bithiophene, 5-alkoxy-2,2′-bithiophenes, 5-N,N-dialkylamino-2,2′-bithiophenes and thiazolyl- and benzothiazolyl diazonium salts as coupling components. The 5-alkoxy-2,2′-bithiophene precursors yielded the 5-thiazolylazo-5′-alkoxy-2,2′-bithiophenes, while the azo coupling reaction of 5-N,N-dialkylamino-2,2′-bithiophenes with the thiazolyl diazonium salt gave 4-thiazolyl-azo-5-N,N-dialkylamino-2,2′-bithiophenes. A different reactivity behavior was observed for 2,2-bithiophene with thiazolyl diazonium salts which gave rise to the expected azo dyes together with several arylation products. The redox behavior, thermal stability, and the first hyperpolarizability of the novel chromophores were evaluated through cyclic voltammetry, thermogravimetric analysis (TGA) and hyper-Rayleigh scattering (HRS) respectively. By varying the position of the thiazolyldiazene acceptor group on the bithiophene system, the electrochemical behavior as well as the optical (linear and nonlinear) properties of the donor–acceptor π-conjugated systems can readily be tuned. Push–pull 5-thiazolylazo-5′-alkoxy-2,2′-bithiophenes exhibit the most promising redox and the solvatochromic properties and second-order nonlinear optical response. The redox and the optical properties also show notable variations for the different heterocyclic spacers and were also sensitive to the electronic acceptor strength of the (benzo)thiazolyldiazene moieties.     

Studies on the synthesis of a methacrylate-based dental restorative resin

The synthesis of bisphenol A–glycidyl methacrylate (BIS–GMA), the resin component in most dental composite restorative materials, catalyzed by different tertiary amine accelerators such as N,N′-dimethyl-p-toluidine (DMPT), N,N′-dimethylamino phenethyl alcohol (DMAPEA), and N,N′-dimethylamino ethyl methacrylate (DMAEMA) is reported in this work. The effect of varying concentrations of accelerators and the reaction conditions of the synthesis as a function of time is studied in detail. The kinetics of the reaction between epoxide and carboxyl group during the formation of BIS–GMA is monitored using infrared (IR) and chemical techniques. The reaction is found to follow first-order and zero-order kinetics with respect to epoxide and acid, respectively. The degree of epoxide and acid conversion has been calculated as a function of time. The percentages of various isomers, formed under different reaction conditions have been reported. Characterization procedures for BIS–GMA have been developed.     

An NMR study of the dissociation of N,N′-(2-propyloximino)-4,4′-methylenebis(phenylcarbamate) and its crosslinking of polymers containing labile hydrogens. II

Nuclear magnetic resonance spectroscopy has been used to study the dissociation and reaction of N,N′-(2-propyloximino)-4,4′-methylenebis(phenylcarbamate), as a crosslinking agent for polymers containing labile hydrogens. The crosslinking of poly(acrylic acid), polyacrylamide, and poly(vinyl alcohol) was found to result upon heating each to 150°C for 10 min with this component at 2–10 wt %.     

Preparation of monodisperse hydrophilic polymer microspheres with N,N′‐methylenediacrylamide as crosslinker by distillation precipitation polymerization

Highly crosslinked cauliflower‐like poly(N,N′‐methylenebisacrylamide) particles were prepared by distillation precipitation polymerization in neat acetonitrile with 2,2′‐azobisisobutyronitrile as initiator. Monodisperse hydrophilic polymer microspheres with various functional groups, such as amide, pyrrolidone and carboxylic acid, with a spherical shape and smooth surface in the size range 120–600 nm were prepared by distillation precipitation copolymerizations of functional comonomers including N‐isopropylacrylamide, N‐vinylpyrrolidone, methacrylic acid with N,N′‐methylenebisacrylamide as crosslinker. The polymer particles were formed and precipitated out from the reaction medium during the distillation of the solvent from the reaction system through an entropic precipitation manner. The effects of the solvent and the degree of crosslinking on the morphology and the loading capacity of the functional groups of the resultant polymer particles were investigated. The resulting polymer particles were characterized with scanning electron microscopy, transmission electron microscopy, dynamic light scattering and Fourier transform infrared spectroscopy. Copyright © 2007 Society of Chemical Industry     

Synthesis and characterization of epoxy-chain end(s) functional macromonomer of polystyrene and its use in photoinitiated cationic polymerization

A novel epoxy chain-end(s) functional polystyrene macromonomer (PSt-CHO) was prepared via free radical polymerization (FRP) of styrene (St) initiated by 4,4′-azobis(3-cyclohexenylmethyl-4-cyanopentanoate) (ACCP) azo initiator and epoxidation on workup with 3-chloroperoxybenzoic acid under inert atmosphere in methylene chloride at 0 °C. 4,4′-Azobis(4-cyanopentanoyl chloride) (ACPC) was obtained by the reaction of 4,4′-azobis(4-cyanopentanoic acid) (ACPA) with phosphorus pentachloride in methylene chloride. The ACCP was synthesized by the condensation reaction of 3-cyclohexene-1-methanol with ACPC. The FRP of styrene with ACCP has yielded polystyrene with cyclohexene end(s) group (PSt-CH). Epoxidation of the PSt-CH was performed using 3-chloroperoxybenzoic acid to obtain epoxy chain-end(s) functional polystyrene macromonomer (PSt-CHO). This macromonomer was used as precursor in photoinitiated cationic polymerization for obtaining brush-type and graft copolymers. Photoinitiated cationic homopolymerization of the macromonomer in the presence of diphenyliodonium salt at λ = 300 nm yielded brush-type polymers. Photoinitiated cationic copolymerization of the macromonomer with cyclohexene oxide (CHO) monomer and diphenyliodonium salt at λ = 350 nm produced graft copolymers. The polymers synthesized were characterized by means of FTIR, ¹HNMR and gel permeation chromatography measurements. All the spectroscopic studies revealed that a macromonomer of polystyrene with cyclohexene oxide (CHO) functionality at the chain end(s) (PSt-CHO) and their brush-type and graft copolymers were obtained.     

Synthesis,spectral properties and application of novel disazo disperse dyes derived from polyester waste

Terephthalic dihydrazide was obtained through aminolytic depolymerisation of polyester bottle waste by using hydrazine hydrate. It was further reacted with 4‐aminobenzoic acid in the presence of polyphosphoric acid to obtain a cyclic compound, 4,4′‐[5,5′‐(1,4)‐phenylene)bis(1,3,4‐oxadiazole‐5,2‐diyl)dianiline, having a heterocyclic moiety. Diazotisation of this compound followed by coupling with various N,N‐disubstituted anilines afford a series of novel disazo disperse dyes. The structures of these synthesised dyes were confirmed by elemental analysis and Fourier Transform–infrared, proton nuclear magnetic resonance and mass spectroscopy. Ultraviolet–visible spectra of these azo dyes in different polar solvents showed considerable variation in the wavelength of maximum absorbance (λ_max). Application of these dyes on polyester and nylon fabrics using high‐temperature dyeing methods gave brilliant yellowish red hues with fair to moderate light fastness and very good to excellent wash fastness and sublimation fastness.     

Atom transfer radical polymerization of styrene initiated by bromoacetylated syndiotactic polystyrene macroinitiator

Atom transfer radical polymerization of styrene was conducted with bromoacetylated syndiotactic polystyrene as macroinitiator and copper bromide combined with N,N,N′,N′,N′‐pentamethyldiethylenetriamine as catalyst. A two‐stage process has been developed to synthesize the macroinitiator. First, syndiotactic polystyrene (sPS) was functionalized in the side phenyl rings with acetyl groups using the Friedel–Crafts reaction; second, the acetyl groups were converted to bromoacetyl groups by an acid‐catalyzed halogenation reaction. The initiator was found to be active in the polymerization of styrene, leading to the production of graft chains with well‐defined structure. The molecular weight and molecular weight distribution of the graft chains were determined using gel permeation chromatography after cleaving from the sPS backbone using peroxide acid oxidation followed by hydrazine‐catalyzed hydrolysis. The results indicated that the polymerization process was characteristic of a ‘living’ nature. Copyright © 2007 Society of Chemical Industry     

Block copolymers obtained by free radical mechanism III. Synthesis in emulsion

Block copolymers were synthesized by a sequential free radical polymerization method with the use of di-t-butyl-4,4′-azobis(4-cyanoperoxyvalerate) as the trifunctional initiator. The polymerizations were carried out in two stages. First, the poly(methyl methacrylate) and poly(butyl methacrylate) polymeric initiators were synthesized by activating, at room temperature, the perester groups of the initiator with tetraethylenepentamine. For the second stage, the reaction ingredients were pre-emulsified, then the azo groups of these polymeric initiators were activated thermally in the presence of either styrene or p-methylstyrene. It was found that the reaction in the emulsion particles followed bulk kinetics, although the average size of the particles was small, 50–100 nm.     

Synthesis,characterization and rheological properties of three different microstructures of water-soluble polymers prepared by solution polymerization

Three different structures were synthesized via solution free radical polymerization. Polyacrylamides hydrophobically modified with small amounts of two different N′N-dialkylacrylamides [N,N-dihexylacrylamide (DHAM) and N,N-dioctylacrylamide (DOAM)] and two different N-alkylacrylamides [N-dodecylacrylamide (DAM) and N-hexadecylacrylamide (HDAM)] have been synthesized using two linear hydrophobic initiators with 12 (ACVA₁₂) and 16 (ACVA₁₆) carbon atoms and two di-substituted hydrophobic initiator with two chains of 6 (ACVA_di6) and 8 (ACVA_di8) carbon atoms derived from 4′4-azobis(4-cyanopentanoic acid) (ACVA). The polymers obtained were telechelic, multisticker and combined. The initiators, monomers and polymers synthesized were characterized by ¹H NMR and light scattering (LS). The rheological properties of these three different associative polymers were investigated using steady-state experiments. The effect of location and structure (linear or di-substituted) of the hydrophobic groups upon the viscosity of the polymer in solution was studied.     

The preparation,characterization, and cure reactions of new bisbenzocyclobutene‐terminated aromatic imides

Several new bisbenzocyclobutene‐terminated aromatic imides, 2,2′‐bis(N‐4‐benzocyclobutenyl) phthalimide, 2,2′‐bis[4‐(N‐4‐benzocyclobutenylphthalimide)]‐ether, 2,2′‐bis[4‐(N‐4‐benzocyclobutenylphthalimide)]‐ketone, and 2,2′‐bis[4‐(N‐4‐benzo cyclobutenylphthalimid‐4‐oxy) phenyl]‐propane, have been synthesized in high yields and characterized by FTIR, MS, EA, and ¹H NMR spectroscopy. The polymers cured from benzocyclobutene‐terminated imides have high glass transition temperature and good thermal stabilities. The cure reaction of an imide was studied by FTIR‐ATR (attenuated total reflection) and DSC techniques. Apparent kinetic parameters of the cure reaction are obtained. The apparent cure reaction order, activation energy, and pre‐exponential factor determined by isothermal DSC method are 1, 143.4 kJ/mol, and 3.88× 10¹³ min^?1, and by nonisothermal DSC methods 1, 139.4 kJ/mol, and 2.27× 10¹³ min^?1, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1705–1719, 2006     

Synthesis and characterization of new optically active poly(amide‐imide‐urethane) thermoplastic elastomers,derived from 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L‐leucine‐p‐aminobenzoic acid) and PEG‐MDI

A new class of optically active poly(amide‐imide‐urethane) was synthesized via two‐step reactions. In the first step, 4,4′‐methylene‐bis(4‐phenylisocyanate) (MDI) reacts with several poly(ethylene glycols) (PEGs) such as PEG‐400, PEG‐600, PEG‐2000, PEG‐4000, and PEG‐6000 to produce the soft segment parts. On the other hand, 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L ‐leucine‐p‐amidobenzoic acid) (2) was prepared from the reaction of 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L ‐leucine) diacid chloride with p‐aminobenzoic acid to produce hard segment part. The chain extension of the above soft segment with the amide‐imide 2 is the second step to give a homologue series of poly(amide‐imide‐urethanes). The resulting polymers with moderate inherent viscosity of 0.29–1.38 dL/g are optically active and thermally stable. All of the above polymers were fully characterized by IR spectroscopy, elemental analyses, and specific rotation. Some structural characterization and physical properties of this new optically active poly(amide‐imide‐urethanes) are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2288–2294, 2004     

Palladium‐Catalyzed N‐Arylation of N,N‐Dialkylhydrazines with Aryl Chlorides

N,N‐Dialkyl‐N′‐arylhydrazines have been prepared usually in high to excellent yields via the reaction of N,N‐dialkylhydrazines with aryl chlorides in the presence of Pd₂(dba)₃, Xphos and NaO‐t‐Bu in dioxane at 120 °C. With ortho‐substituted aryl chlorides best results have been obtained by using 2‐(2′,6′‐dimethoxybiphenyl)dicyclohexylphosphine (ligand d) as the ligand.     

Epoxy resins based on aromatic glycidylamines. IV. Preparation of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane from aniline and analysis of the product by GPC and HPLC

Epoxy resins containing N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) were prepared from aniline and epichlorohydrin and analyzed by GPC and HPLC. The product composition was compared with that of resins prepared from 4,4′-diaminodiphenylmethane (DDM) and epichlorohydrin, which had been analyzed in our previous work. A new byproduct designated Y4 was isolated by semipreparative HPLC and identified by NMR and mass spectroscopy. The course of formaldehyde condensation with N,N-dichlorohydrin of aniline (DCHA) was followed by GPC and HPLC and the mechanism of formation of Y4 was proposed on the basis of obtained results. Attention was also paid to the differences in reactivity of DCHA diastereoisomers.     

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

In 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.     

Wet spinning of solid polyamic acid fibers

Recent research at the NASA Langley Research Center has involved the production of polyamic acid fibers from resins derived from the reaction of 3,3′,4,4′-benzophenonetetra-carboxylic dianhydride and 3,3′-diaminobenzophenone or 4,4′-oxydianiline in N,N-dimethylacetamide. Resins were extruded into aqueous solutions of ethylene glycol, ethanol, or N,N-dimethylacetamide in order to induce filament formation. These filaments were then washed in water and dried using air or vacuum ovens. Fractured fiber ends were examined using an optical or scanning electron microscope for the presence of macropores, termed voids. Coagulation bath concentration and composition, resin inherent viscosity, resin % solids, and filament diameter were studied to determine their effect on the production of solid core fibers.     

Synthesis and characterization of a novel oligosiloxane containing alternative ladderlike structure via charge‐transfer interaction

A novel oligosiloxane containing alternative ladderlike structure involving viologen groups has been prepared via donor–acceptor interaction‐assisted template polymerization. The monomer used as the electron‐donor component, N,N ′‐bis(3‐methyldimethoxyl‐silylpropyl)‐4,4′‐bipyridinium dihexafluorophosphate and its precursor, N,N ′‐bis(3‐methyldimethoxyl‐silylpropyl)‐4,4′‐bipyridinium dibromide were first synthesized successfully in high yield. This oligosiloxane, which displays interesting electrochromic properties, has been characterized by FTIR, UV–vis, ¹H NMR, ²⁹Si NMR, X‐ray diffraction (XRD), and vapour pressure osmometry (VPO). © 2001 Society of Chemical Industry     

Synthesis and characterization of novel optically active poly(amide–imide)s containing N,N′‐(pyromellitoyl)‐bis‐L‐valine diacid chloride and 5,5‐disubstituted hydantoin derivatives under microwave irradiation

Pyromellitic dianhydride (1,2,4,5‐benzenetetracarboxylic acid 1,2,4,5‐dianhydide) was reacted with L ‐valine in a mixture of acetic acid and pyridine (3:2) at room temperature, and then was refluxed at 90–100 °C, N,N′‐(pyromellitoyl)‐bis‐L ‐valine diacid was obtained in quantitative yield. The imide–acid was converted to N,N′‐(pyromellitoyl)‐bis‐L ‐valine diacid chloride by reaction with thionyl chloride. Rapid and highly efficient synthesis of a number of poly(amide–imide)s was achieved under microwave irradiation using a domestic microwave oven by polycondensation of N,N′‐(pyromellitoyl)‐bis‐L ‐valine diacid chloride with six different derivatives of 5,5‐disubstituted hydantoin compounds in the presence of a small amount of a polar organic medium that acts as a primary microwave absorber. A suitable organic medium was o‐cresol. The polycondensation proceeded rapidly, compared with conventional melt polycondensation and solution polycondensation and was almost completed within 8 min, giving a series of poly(amide–imide)s with inherent viscosities in the range 0.15–0.36 dl g^?1. The resulting poly(amide–imide)s were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, elemental analysis, inherent viscosity (η_inh) measurements, solubility testing and specific rotation measurements. The thermal properties of the poly(amide–imide)s were investigated by using thermogravimetric analysis. Copyright © 2004 Society of Chemical Industry     

Microwave assisted novel synthetic route for polyfluorenes containing triphenylamine and solubilizing alkyl moiety for blue emitting diodes

A series of blue electroluminescent polyfluorenes (PFs) containing triphenylamine and various alkyl moieties were synthesized using an Ni(0) mediated C?C Yamamoto coupling reaction assisted by microwaves. The synthesized PFs were characterized by various spectroscopic techniques. Their absorption and photoluminescence properties were investigated in solvent and found to possess characteristic electronic absorption and emission spectra. These PFs were found to emit in the blue region (407?415 nm) with high quantum yield in the range 0.41?0.73. Cyclic voltammetry studies of the PFs revealed that the compounds were stable under redox conditions with highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital in the range 5.24–5.29 eV and 1.98?2.01 eV, respectively. The E_HOMO for the PFs was similar to the most widely used hole transporting materials N,N′‐Di(1‐naphthyl)‐N,N′‐diphenyl‐(1,1′‐biphenyl)‐4,4′‐diamine (NPD), N,N′‐Bis(3‐methylphenyl)‐N,N′‐diphenylbenzidine (TPD) and N²,N²,N²′,N²′,N⁷,N⁷,N⁷′,N⁷′‐octakis(4‐methoxyphenyl)‐9,9′‐spirobi[9H‐ fluorene]‐2,2′,7,7′‐tetramine, Spiro‐OMeTAD (spiro‐OMe‐TAD). The thermal stability observed for the PFs accounts for their use under ambient conditions. The electrochemical studies of the fabricated polymer light emitting diodes suggest that the PFs have potential to be used as hole transporting and blue electroluminescent materials for optoelectronic devices. © 2017 Society of Chemical Industry     

Water Solvent Method for Esterification and Amide Formation between Acid Chlorides and Alcohols Promoted by Combined Catalytic Amines: Synergy between N‐Methylimidazole and N,N,N′,N′‐Tetramethylethylenediamine (TMEDA)

An efficient method for esterification between acid chlorides and alcohols in water as solvent has been developed by combining the catalytic amines, N‐methylimidazole and N,N,N′,N′‐tetramethylethylenediamine (TMEDA). The present Schotten–Baumann‐type reaction was performed by maintaining the pH at around 11.5 using a pH controller to prevent the decomposition of acid chlorides and/or esters and to facilitate the condensation. The choice of catalysts (0.1 equiv.) was crucial: the combined use of N‐methylimidazole and TMEDA exhibited a dramatic synergistic effect. The catalytic amines have two different roles: (i) N‐methylimidazole forms highly reactive ammonium intermediates with acid chlorides and (ii) TMEDA acts as an effective HCl binder. The production of these intermediates was rationally supported by a careful ¹H NMR monitoring study. Related amide formation was also achieved between acid chlorides and primary or secondary amines, including less nucleophilic or water‐soluble amines such as 2‐(or 4‐)chloroaniline, the Weinreb N‐methoxyamine, and 2,2‐dimethoxyethanamine.