Intramolecular cyclization of pendant phenylethynyl groups as a route to solvent resistance in polyphenylquinoxalines

Biphenyl-based bisbenzil monomers which contain pendant phenylethynyl groups in the 2,2′-positions were condensed with 3,3′-diaminobenzidine to make polyphenylquinoxalines (PPQs) of high molecular weight. Thermal cure of these polymers at 193°C caused an intramolecular cyclization (IMC) of the phenylethynyl groups to give the rigid 9-phenyldibenzanthracene system in the backbone of the polymer. The initial, uncured polymers formed though films which were soluble in m-cresol and chlorinated solvents, but after thermal cure the films became insoluble in all common organic solvents and acids while maintaining their toughness. DSC scans of the cured materials showed small residual exotherms indicating that after vitrification even the intramolecular rotation required for the IMC reaction became restricted.     

Investigation of reactions of the organozinc reagents prepared from zinc and dialkyl dibromomalonates with the derivatives of 2-arylmethyleneindan-1,3-dione and 5-arylmethylene-2,2-dimethyl-1,3-dioxane-4,6-dione

Organozinc compounds prepared from dialkyl dibromomalonates and zinc react with 2-arylmethyl-eneindan-4,6-diones, 5-arylmethylene-2,2-dimethyl-1,3-dioxane-4,6-diones, as well as with 2-[4-(1,3-dioxoindan-2-ylidenemethyl)phenyl]methyleneindan-1,3-dione and 5-[4-(2,2-dimethyl-4,6-dioxo-1,3-dioxane-2-ylidenemethyl)phenyl]methylene-2,2-dimethyl-1,3-dioxane-4,6-diones to form dialkyl 3-aryl-1′3′-dioxaspiro(cyclopropane-2,2′-indan)-1,1-dicarboxylates, dimethyl 3-aryl-6,6-dimethyl-5,7-dioxa-4,8-dioxaspiro[2,5]octan-2,2-dicarboxylates, dialkyl 2-{4-[3,3-bis (alkoxycarbonyl)-1′,3′-dioxaspiro(cyclopropane-2,2′-indan)-1-yl]phenyl}-1′,3′-dioxaspiro[cyclopropane-2,2′-indan]-1,1-dicarboxylates, and dialkyl 2-{4-[2,2-bis(alkoxycarbonyl)-6,6′-dimethyl-4,8-dioxo-5,7-dioxaspiro[2,5]oct-1-yl]phenyl}-6,6-dimethyl-4,8-dioxo-5,7-dioxaspiro[2,5]octan-1,1-dicarboxylate respectively.     

New processable polyaromatic amides curable by intramolecular cyclization. XVI

New Processable Polyaromatic amides were prepared from 2,2′-diiododiphenyl-4,4′-dicarbonyl dichloride (I) and several aromatic diamines. Phenylethynyl groups were introduced in these polymides by replacing the iodine groups with copper phenyl acetylide. On thermal curing, 2,2′-di(phenylethynyl)biphenyl group undergoes intramolecular cyclization to form 9-phenyl dibenzanthracene derivative. The cured polymers showed increased heat and chemical stabilities. No melting points were observed for all the polymers below 500°C. The viscosity of the polymers was decreased on substitution of the iodine by phenylethynyl groups.     

Phenylethynyl-terminated imide oligomers and polymers therefrom

Two new phenylethynyl endcapping compounds, 3- and 4-amino-4′-phenylethynylbenzophenone, were synthesized and used to terminate imide oligomers from 3,4′-oxydianiline and 4,4′-oxydiphthalic anhydride at a calculated molecular weight of 9000 g/mol and from 3,4′-oxydianiline (0.85 mol), 1,3-bis (3-aminophenoxy) benzene (0.15 mol), and 3,3′,4,4′-biphenyltetracarboxylic dianhydride at a calculated molecular weight of 5000 g/mol. Glass transition temperatures for the cured oligomers were ～ 249°C for the former and 272°C for the latter. Films cured at 350°C for 1 h were tough and flexible and provided high tensile properties. The uncured oligomers were readily compression molded to provide tough, solve nt-resistant moldings. © 1994 John Wiley & Sons, Inc.     

The Pursuit of Perphenylterphenyls

Tetradecaphenyl-p-terphenyl ( 2 ) was synthesized from 2,3,5,6-tetraphenyl-1,4-diiodobenzene ( 11 ) by two methods. Ullmann coupling of 11 with pentaphenyliodobenzene ( 9 ) gave compound 2 in 1.7 % yield, and Sonogashira coupling of 11 with phenylacetylene, followed by a double Diels-Alder reaction of the product diyne 12 with tetracyclone ( 6 ), gave 2 in 1.5 % overall yield. The latter reaction also gave the monoaddition product 4-(phenylethynyl)-2,2′,3,3′,4′,5,5′,6,6′-nonaphenylbiphenyl ( 13 ) in 4 % overall yield. The X-ray structures of compounds 2 and 13 show them to possess core aromatic rings distorted into shallow boat conformations. Density functional calculations indicate that these unusual structures are not the lowest energy conformations in the gas phase and may be the result of packing forces in the crystal. In addition, while uncorrected DFT calculations indicate that the strain energy in compound 2 is approximately 50 kcal/mol, dispersion-corrected DFT calculations suggest that it is essentially unstrained, due to compensating, favorable, intramolecular interactions of its many phenyl rings. An attempted synthesis of tetradecaphenyl-o-terphenyl ( 4 ) by reaction of diphenylhexatriyne ( 14 ) with three equivalents of tetracyclone at 350 °C gave only the diadduct 2-(phenylethynyl)-2′,3,3′,4,4′,5,5′,6,6′-nonaphenylbiphenyl ( 15 ) in 17 % yield. Even higher temperatures failed to produce 4 and lowered the yield of 15 , perhaps due to rapid decomposition of the starting materials. Ullmann coupling of 3,4,5,6-tetraphenyl-1,2-diiodobenzene ( 16 ) and compound 9 also failed to give compound 4 .     

Phenylethynyl-pendant polyphenylquinoxalines curable by an intramolecular cycloaddition reaction

Polyphenylquinoxalines containing 2,2′-bis(phenylethynyl)diphenylene moieties along the polymer backbone have been synthesized. As anticipated, these polymers were found to undergo a novel curing reaction consisting of an intramolecular cycloaddition (IMC) of pendant groups to a dibenzoanthracene backbone structure. The IMC reduces chain mobility, and the fused ring structure increases the glass transition temperature of the polymer. The potential of this approach to curing high-temperature polymers was demonstrated in the processing of one such polymer having an initial T_g of 215°C. Curing at 245°C with no evolution of volatiles produced a T_g of 365°C. This very significant increase in potential use temperature via a volatiles-free IMC cure provides promise for a tough phenyiquinoxaline resin system which can be used to fabricate reinforced composites that have use temperatures far exceeding processing temperatures.     

Syntheses of three naturally occurring polybrominated 3,3′-bi-1H-indoles

The naturally occurring polybrominated indoles 2,2′,5,5′-tetrabromo-3,3′-bi-1H-indole, 2,2′,6,6′-tetrabromo-3,3′-bi-1H-indole, and 2,2′,5,5′,6,6′-hexabromo-3,3′-bi-1H-indole were synthesized using a palladium catalyzed, carbon monoxide mediated, double reductive N-heterocyclization of 2,3-bis(2-nitro-4(or 5)-bromophenyl)-1,4-butadienes as the key step.     

天然产物Angustifolin D中间体的合成

以3,4,5-三甲氧基苯甲酸为原料,经6步反应以23％总收率完成了Angustifolin D关键中间体--6,6′-2［(Z)-2-碘代-1-丙烯基］-2,2′,3,3′,4,4′-六甲氧基-1,1′-联苯(7)的合成,其结构经¹H NMR, ¹³C NMR, IR和MS确证。其中关键步骤联苯偶连反应采用了廉价易得的铜试剂(CuBr·SMe₂)作为催化剂。     

Thermolysis of 3-phenyl-5-arylamino-1,2,4-oxadiazole and thiadiazole derivatives

Thermal reactions of 3-phenyl-5-arylamino-1,2,4-oxadiazoles I and II were investigated. Neat heating at ca. 250°C for 6 hours afforded H₂O, benzonitrile, arylcyanamides, arylamines, azobenzene, benzimidazole derivatives, and 3,3′-diphenyl-5,5′-bis[1,2,4-oxadiazolyl]. Analogous results were obtained by the thermolysis of 3-phenyl-5-anilino-1,2,4-thiadiazole III at ca. 200°C for 2 hours. In addition to H₂S, NH₃, and HNCS, phenyl isothiocyanate and thiocarbanilide were obtained. Thermolysis of III in quinoline as a radical trap gave analogous resuLts but also 2-anilinoquinoline. A free-radical mechanism has been suggested to account for the identified products. © 1997 John Wiley & Sons, Inc.     

Thermal degradation of a polyphenylimide-quinoxaline in air and under vacuum

Three samples of poly{2,2′-[N,N′-bis(1,4-phenylene)benzophenone-3,3′,4,4′-tetracarboxylimide-6,6′-bis(3-phenyl-quinoxaline)]} (PPIQ), were prepared, differing in molecular weights and polymer chain endings. Their thermal degradation in vacuo and in air was determined by isothermal weight loss measurements. As in the case of poly-[2,2′-(1,4-phenylene)-6,6′-bis(3-phenylquinoxaline)] (PPQ), the temperature coefficients of thermal degradation in air were independent of molecular weight. However, in contrast, the temperature coefficients were independent of the type of polymer endgroups. It is, therefore, concluded that, contrary to amino-terminated PPQ's, polymer chain-end unzipping of PPIQ is of minor importance during thermal-oxidative degradation.     

Synthesis and thermal studies of bisphenol-A based bismaleimide

The compound 2,2-bis[4-(4-maleimidophenoxy phenyl)]propane was prepared by the imidization of bisamic acid of 2,2-bis(4-aminophenoxy phenyl)propane. Various nanoclays were blended with this bismaleimide and thermally cured. The structural characterization of the synthesized materials and the thermal properties of the bismaleimide and their blends were investigated through FTIR, ¹H and ¹³C NMR, differential scanning calorimetry and thermo gravimetric analysis. Among the various clays investigated, Cloisite 15A shows strong influence on the cure exotherm of bismaleimide. Introduction of clay mineral into bismaleimide shifts the onset of curing exotherm to higher temperature and is nearly 40 °C. The thermal stability of the clay loaded cured bismaleimide increases and the presence of clay particles in the cured bismaleimide matrix enhances the char formation.     

Thermal behaviour of ethynyl and ethenyl terminated imide resins

A series of ethynyl and ethenyl end-capped imide resins were synthesised by the reaction of 9,9-bis(4-aminophenyl) fluorene (BAF) with pyromellitic dianhydride (PMDA)3/3′, 4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxy phenyl) hexafluoropropane dianhydride (6F) and 3-ethynyl aniline/maleic anhydride. Structural characterisation was done by infra red and elemental analysis. Thermal characterisation was done by differential scanning calorimetry and thermogravimetric analysis. The decomposition temperatures of cured resins were above 200°C in nitrogen atmosphere. Char yield at 800°C ranged from 59–65.5%.     

C2-Symmetric sulfur derivatives of 2,2′,3,3′-tetramethoxybiphenyl

A practical route to prepare dithioether, thiophene and thiophene S-dioxide derivatives of 2,2′,3,3′-tetramethoxy-1,1′-biphenyl 1 is described. Resolution of 6,6′-bis(methylthio)-3,3′-dimethoxy-[1,1′-biphenyl]-2,2′-diol 15 was achieved and its absolute configuration was assigned by X-ray analysis of the corresponding phosphorothioamidate diastereomer 18.     

Synthesis and characterization of 3-phenylethynyl endcapped matrix resins

The synthesis of 3-phenylethynylphenol, and its applicability as a high temperature cross-linking endcap for high T_g polyarylene ethers is described. It was synthesized in high yields and purity using the palladium catalyzed coupling reaction between the protected 3-bromo or iodo phenol and phenylacetylene. The yield of the reaction was found to be highly dependent on the structure of the halide used, the reaction temperature, and the concentration of phenylacetylene. The use of the protected phenol in the palladium catalyzed reaction was also extended to the high yield synthesis of 3-ethynylphenol and protected 4-ethynylphenols. The complete synthesis of 3-phenylethynylphenol, 3-ethynylphenol, and protected 4-ethynylphenol in high yields has been demonstrated and is discussed herein. Three new phenylethynyl functionalized arylene ether matrix resins have been synthesized in high yields and purity by reacting 3-phenylethynylphenol with 4,4′-dichlorodiphenyl sulfone, 4,4′-difluorobenzophenone, and bis(4-fluorophenyl)phenyl phosphine oxide, via nucleophilic poly(arylene ether) synthesis conditions. These low molecular weight materials undergo thermally induced chain extension/branching to yield an insoluble three-dimensional network at reaction temperatures of around 380°C. The low molecular weight arylene ethers endcapped with the phenylethynyl group demonstrate excellent flow characteristics and a wide processing window of about 250°C. Crosslinking of the 4,4′-bis(3-phenylethynyl phenoxy)diphenyl sulfone system for 30 min at 350°C in air afforded a T_g value of 265°C by differential scanning calorimetry measurements. Trace metal analysis for palladium and copper showed absence of these metals that would otherwise detract from the excellent thermal stability. The synthesis and characterization of these phenylethynyl endcapped arylene ether matrix resins is discussed. © 1995 John Wiley & Sons, Inc.     

Model photostable compounds

The photostabilities and syntheses of 2,2′-bis(o-hydroxyphenyl)-5,5′-bipyrimidine, 6,6′-bis(o-hydroxyphenyl)-3,3′-bipyridine and 3,8-bis(o-hydroxyphenyl)-4,7-phenanthroline are discussed. The syntheses of parent compounds lacking the o-hydroxy groups are also described.     

New approaches towards the synthesis and characterization of alkoxy substituted spirobifluorenes and spirosilabifluorenes for organic optoelectronics

Alkoxy substituted spirobifluorene derivatives namely 2,2′,7,7′-tetrabromo-3,6-bis(methoxy)-9,9′spirobifluorene (MSBF), 2,2′,7,7′-tetrabromo-3,6-bis(ethoxy)-9,9′spirobifluorene (ESBF), 2,2′,7,7′-tetrabromo-3,6-bis(butoxy)-9,9′spirobifluorene (BSBF), 2,2′,7,7′-tetrabromo-3,3′,6,6′-tetra(methoxy)-9,9′-spiro-9-silabifluorene (MSSiBF) and their key intermediates have been synthesised successfully. All compounds have been fully characterised by ¹H and ¹³C NMR, FTIR, UV-visible spectroscopy, MS spectrometry. TGA analysis revealed good thermal stability. The systematic investigation on the solubility, thermostability and photophysical property of synthesized compound showed that alkoxy substituted spirobifluorene were unique in rigidity and have wide range of applications in molecular electronics and can be used as building units for optoelectronics material.     

Reformatsky Reaction of Methyl 1-Bromocycloalkanecarboxylates with α-Dicarbonyl Compounds

Reformatsky reactions of methyl 1-bromocyclohexanecarboxylate and methyl 1-bromocyclo-pentanecarboxylate with 2-aryl-2-oxoacetaldehydes involve both carbonyl groups of the latter and result in formation of 3a-aryl-3,3 : 6,6-bis(pentamethylene)- and 3a-aryl-3,3 : 6,6-bis(tetramethylene)tetrahydrofuro-[3,2-b]furan-2,5-diones. The reaction with 2-(2,4-dimethylphenyl)-2-oxoacetaldehyde gives acyclic products, methyl 1-[1-hydroxy-2-(2,4-dimethylphenyl)-2-oxoethyl]cyclohexanecarboxylate and methyl 1-[1-hydroxy-2-(2,4-dimethylphenyl)-2-oxoethyl]cyclopentanecarboxylate, while with benzil methyl 1-(4-hydroxy-1-oxo-3,4-diphenyl-2-oxaspiro[4.5]dec-3-yl)cyclohexanecarboxylate and methyl 1-(4-hydroxy-1-oxo-3,4-diphenyl-2-oxaspiro[4.4]non-3-yl)cyclopentanecarboxylate are obtained.     

Preparation of poly(phosphate ester)s having bisphenol moieties as mesogenic units in the main chain

Poly(phosphate ester)s, PPE 1a–d , were synthesized from polycondensation of methyl phosphorodichloridate (MPDC) with various bisphenols such as 4,4′-biphenol 1a , 4,4′-dihydroxyphenylether 1b , bis(4-hydroxyphenyl)methane 1c , and 3,3′-dimethyl-4,4′-dihy-droxybiphenyl 1d . PPE 2a–d with hexamethylene spacers were also obtained from poly-condensation of MPDC with 4,4′-bis(6-hydroxyhexyloxy)biphenyl 2a , 4,4′-di(6-hydroxyhexyloxy)phenyl ether 2b , bis[4-(6-hydroxyhexyloxy)phenyl]methane 2c , and 3,3′-dimethyl 4,4′-di(6-hydroxyhexyloxy)biphenyl 2d . The degree of crystallinity of PPE 1a–1d without hexamethylene spacer was 3.3–17.6%, whereas PPE 2a and PPE 2b which exhibit mesomorphic behavior were 20.1 and 18.6%, respectively. PPE 2a and PPE 2b show the mesophase at 139.6–195.5°C and 42.4–66.3°C, respectively. PPE 2c and PPE 2d were obtained as rubbery. From pyrolysis of PPE in air the temperature corresponding to 5% weight loss was found to be 322–408°C and 284–291°C for PPE 1 and PPE 2 , respectively. It was also found that PPE 2a was enzymatically degraded by phospholipase C. © 1994 John Wiley & Sons, Inc.     

Synthesis and performance study of a novel sulfonated polytriazole proton exchange membrane

Sulfonated polytriazole (SPTA) proton exchange membranes (PEMs) with a series of sulfonation degrees was synthesized based on click chemistry from a rigid diazide monomer, 4,4′-bis(azidomethyl)-1,1′-biphenyl (BAMB), with 2,2-bis[(4-propargyloxy)phenyl]propane (BPBPA) and 4,4′-diazido-2,2′-stilbenedisulfonic acid disodium salt (DSDA). The structure of the copolymers was characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). As a result of the introduction of rigid biphenyl structure and the ionic interaction between triazole rings and sulfonic acid groups, the SPTA membranes exhibited higher water uptake and lower swelling ratio compared to NRE211 membrane, indicating excellent dimensional stability. AC impedance revealed that the proton conductivity of SPTA membranes ranged from 2.5 to 35 mS/cm at 30 °C and 13–105 mS/cm at 80 °C. Besides, the membranes have high thermal and oxidative stability, good mechanical property, and low methanol permeability as well.     

Synthesis and evaluation of novel polyimides derived from spirobichroman diether anhydride

A spirobichroman structure-containing diether anhydride (SBCDA), 6,6′-bis(3,4-dicarboxyphenoxy)-4,4,4′,4′,7,7′-hexamethyl-2,2′-spirobichroman dianhydride, was prepared by the nucleophilic nitrodisplacement of 4-nitrophthalonitrile with the phenolate ion of 6,6′-dihydroxy-4,4,4′,4′,7,7′-hexamethyl-2,2′-spirobichroman, followed by alkaline hydrolysis of the intermediate tetranitrile and dehydration of the resulting tetraacid. A series of high molecular weight poly(ether imide)s with inherent viscosities between 0.45 and 1.28 dL/g were synthesized from SBCDA and various aromatic diamines via a conventional two-stage procedure that included ring-opening polyaddition in N,N-dimethylacetamide (DMAc) to give poly(amic acid)s, followed by thermal cyclization to poly(ether imide)s. The intermediate poly(amic acid)s had inherent viscosities of 0.70–1.50 dL/g. Except for the poly(ether imide) obtained from p-phenylenediamine, the other poly(ether imide)s were soluble in various organic solvents and could be solution-cast into transparent, flexible, and tough films. These poly(ether imide)s had glass transition temperatures in the range 175–262°C and showed no significant decomposition below 420°C, with 10% weight loss being recorded above 446°C in nitrogen or air. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2801–2809, 1997