Preparation of polyamides containing para-linked dimethylbiphenylene moieties

A series of wholly aromatic polyamides containing 3,3′-dimethylbiphenyl-4,4′-dicarboxylic acid (P-DMBA) and 3,4′-dimethylbiphenyl-4,3′-dicarboxylic acid (Q-DMBA) was prepared by the direct polycondensation method using triphenylphosphite and pyridine. Most of the polymers are readily soluble in polar aprotic solvents such as N-methyl-2-pyrrolidone (NMP), N,N′-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), pyridine (py), and m-cresol and could be cast into tough and flexible films. The solubilities of copolyamides containing P-DMBA and Q-DMBA as acid components were remarkably improved. These were characterized by inherent viscosity, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical spectrometry (DMS) measurements. The glass transition temperatures of these polymers were in the range of 200–300°C and the 5% weight loss temperatures were 430–470°C. Films prepared by casting from polymer solutions exhibited good tensile properties. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:847–853, 1998     

Colloidal scale blend of rigid and flexible polyamides

Summary A two step procedure was employed to prepare a colloidal scale, uniform dispersion poly(p-aminobenzoic acid) (PAB) in Nylon 6(3)T. In the first step, a colloidal suspension of PAB was prepared via direct polycondensation, starting from a concentrated solution of AB in dimethyl acetamide (DMAc) containing suitable activators. In the second step, a solution of Nylon 6(3)T in DMAc was mixed with the colloidal suspension. The composite powder was generated by precipitation in water and the composite film obtained by redispersing the powder in DMAc and casting. The films contain PAB particles, below 100 nm in size, uniformly distributed in the Nylon 6(3)T matrix. The mechanical properties and the thermal transitions of these composites were investigated.     

Synthesis of aromatic-aliphatic polyamides containing azo linkage

Summary Two inherently coloured polyamides containing aromatic azo unit in their backbone were synthesised from 4,4-diaminoazobenzene (1) and two aliphatic dicarboxylic acid chlorides (2a, 2b) using N-methyl pyrrolidone (NMP) and N,N-dimethyl acetamide (DMAc) as solvents by the low temperature solution polycondensation method. The polymers were characterised by inherent viscosity, solubility, infra-red and UV-visible spectroscopy. Thermogravimetric analysis of the polymers was carried out to study polymer stability.     

Dry-jet wet spinning of aromatic polyamic acid fiber using chemical imidization

A solution of about 15% polyamic acid (PAA) prepared from 4,4′-oxydianiline and pyromellitic dianhyride in N,N-dimethyl acetamide (DMAc) was used for fiber spinning. To obtain a high draw ratio of the PAA fiber during spinning, acetic anhydride or acetic anhydride and pyridine were added to the PAA solution to make it slightly gelled; such gelling contributed to high drawing of the PAA fibers during spinning. Before spinning the properties of the solution after acetic anhydride or acetic anhydride and pyridine were added, and the diffusion property of DMAc into various coagulants were examined. Even though acetic anhydride was only added to the spinning solution, the diffusion rate became slower and the solution viscosity increased, because PAA was converted to the corresponding polyimide (PI). Pyridine affected the rate dramatically. The mechanical properties of the PAA fibers obtained in this system were examined. Solid PI fibers were also obtained by annealing of the PAA fibers. The ultimate stress and initial modulus of the PAA fiber were around 268 MPa and 4.1 GPa, respectively. After the fiber was annealed at 350°C without tension for 30 min under nitrogen, these values increased to around 399 MPa and 5.2 GPa, respectively.     

A novel preparation of polyimide/clay hybrid films with low coefficient of thermal expansion

A novel polyimide (PI)/clay hybrid nanocomposite, designated as PI (PAAS)/CM, has been developed from the poly(amic acid) salt of triethylamine and organomontmorillonite (CM) using a mixture solution of tetrahydrofuran (THF) and methanol (MeOH). For comparison, two other PI/clay hybrids derived from poly(amic acid) and CM in THF/MeOH solution and N,N′‐dimethylacetamide (DMAc) solution, denoted as PI/CM (T/M) and PI/CM (DMAc), respectively, were also prepared. Dispersion of CM in polymer matrix, tensile properties, and thermal expansion properties of the three hybrids were investigated. Results show that PI (PAAS)/CM has the best dispersion of CM in polymer matrix, highest elongation, and lowest coefficient of thermal expansion values in all hybrids presented in this report. In addition, PI/CM (T/M) has better dispersion of CM and lower coefficient of thermal expansion value than PI/CM (DMAc). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 289–294, 2001     

Effects of processing parameters on morphology of electrospun polystyrene nanofibers

This study focused on the preparation of electrospun polystyrene (PS) nanofibers. PS solutions were prepared in single (dimethylformamide; DMF, dimethylacetamide; DMAc or tetrahydrofuran; THF) and mixed solvent (DMF/THF and DMAc/THF) systems with and without tetrabutylammonium bromide (TBAB) salt. The effects of PS concentration, solvent system, the addition of salt, appearance and diameter of PS fibers were examined. The average diameter of the as-spun fibers increased upon increasing PS concentration. The morphology of the fibers significantly depended on the properties of the solvents. The obtained fibers were smooth without any beads and their diameters were affected by the amount of THF in the solvent and PS concentration. The beads in the fibers disappeared and the fiber diameter significantly decreased after the addition of TBAB. The smallest diameter and the narrowest diameter distribution of PS nanofibers (376±36 nm) were obtained from 15% PS solution in DMAc with 0.025% w/v TBAB.     

Synthesis and properties of polybenzimidazobenzophenanthrolines

Polycondensation of 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) with 3,3′-diaminobenzidine (DAB) and 3,3′4,4′-tetraaminodiphenyl ether (TADPE), respectively, in N,N′-dimethylacetamide (DMAc) at room temperature was found to produce high-viscosity polybenzimidazobenzophenanthroline (PBIPA) precursors. The PBIPA films, exhibiting excellent thermal and mechanical properties, were conveniently prepared by the heat cure of precursors. UV-vis spectra and IR spectra of PBIPA were measured. The permeability to H₂, O₂, and N₂ of these two polymer membranes was determined at 30°C and 1 atm. © 1995 John Wiley & Sons, Inc.     

A study on UV-curable adhesives for optical pick-up: II. Silane coupling agent effect

Ultraviolet curable optical pick-up adhesive composites composed of acrylic and methacrylic mono-, bi- and trifunctional monomers and two kinds of urethaneacrylate oligomers have been easily prepared. In this paper, we studied the influence of various silane coupling agents to enhance the adhesion property in thermal and humid conditions by acting as both inorganic surface and organic polymer modifiers. Among them, vinyltriethoysilane (VTES) provides good adhesion effects on acrylate binder as well as silica surface. VTES added adhesives were studied by the real time FT-IR. The reliability of adhesives was explained by thermal-mechanical analysis (TMA) and then durability was tested by water boiling test. These UV-adhesives were successfully applied and settled in CD and DVD optical pick-up bodies in commercial application.     

Forced torsional properties of PMR composites with varying nadic ester concentrations and processing histories

PMR polyimide resin was prepared from 4,4′-methylenedianiline (MDA), the dimethyl ester of 3,3′,4,4′- benzophenonetetracarboxylic acid (BTDE) and the monomethyl ester of 5-norbornene-2,3-dicarboxylic acid (NE). The NE group serves as a chain terminator and crosslinking site. PMR/Celion 6000 composites were fabricated from resins having varying NE concentrations using two molding processes, and the laminates characterized in forced torsion. Glass transition temperatures (T_g) of 360–390°C were observed in the crosslinked resins, as compared with the literature value of 284°C reported for the uncrosslinked systemT_g did not decrease with decreasing NE concentrations over the range from 2.0 to 1.25 moles. Stoichiometry, within the range studied, showed little influence on shear properties; however, a 25% variation in matrix shear modulus with processing was observed. The G₁₂ values determined in forced torsion were in excellent agreement with those reported from tensile tests of ±45° laminates. A branching and possible secondary crosslink mechanism is proposed based on dynamic mechanical behavior and infrared spectra of the composites.     

Synthesis of poly(N,N-dimethylcarbamoylmethylene) as a polymer homolog of N,N-dimethylacetamide

Summary A novel polymer homolog of N,N-dimethylacetamide (DMAc) having amide groups on all main chain carbons, poly(N,N-dimethylcarbamoylmethylene) 1, was prepared by heating poly(di-t-butyl fumarate) 2 at 180 °C for 2 hours followed by treatment with hexamethylphosphoramide at 180 °C for 5 hours. The structure of the obtained polymer 1 was confirmed by ¹H-, ¹³C-NMR and IR spectroscopy. The polymer 1 actually showed the properties based on its repeating structures. 1 had the amphiphilicity and was soluble both in protic and aprotic solvents. Furthermore, 1 showed the miscibility with commodity polymers such as poly(N-vinylpyrrolidone), poly(vinyl alcohol) and poly(vinyl chloride). In comparison with another polymer homolog of DMAc, poly(2-methyl-2-oxazoline), the polymer 1 exhibited better miscibility with poly(N-vinylpyrrolidone). Received: 24 June 1999/Accepted: 19 July 1999     

Synthesis and the properties of novel cycloaliphatic-aromatic polyamides having pendent N,N'-diphenyl imido groups

: We have investigated a novel monomer having two pendent phenyl imido groups for preparing new cycloaliphatic-aromatic polyamides. Novel polyamides were synthesized by direct polycondensation reaction of N,N'-diphenyl-2,3,5,6-diimido cyclohexane-1,4-dicarboxylic acid(PICA) and various aromatic diamines such as p-phenylene diamine, 4,4'-oxydianiline and 4,4'-methylene dianiline. A direct polycondensation was carried out by a Yamazaki method which is typical of using triphenyl phosphite, lithium chloride, and pyridine. Inherent viscosity of these resulting polyamides are ranged 0.20 ∼ 0.45 dl/g. A transparent flexible and tough film was casted. The glass transition temperature of the polyamide from the PICA and 4,4'-oxydianiline is 147 °C. The decomposition temperature of these polyamides are ranged from 350 ∼ 360 °C and the ash contents of them orders MDA > p-PDA > ODA according to kinds of the using diamines. And the solubilities of these polyamides are good in aprotic solvents such as DMAc, NMP, DMF. Received: 26 July 1999/Revised version: 14 September 1999/Accepted: 28 September 1999     

Morphology of a hydrogen-bonded LC polymer prepared by photopolymerization-induced phase separation under an isotropic phase

A hydrogen-bonded LC polymer was prepared by photopolymerization of an LC blend composed of 4-(6-acryloyloxyhexyloxy)benzoic acid (A6OBA) and 4-hexyloxy-4′-cyanobiphenyl (6OCB), containing small amounts of an inhibitor and photoinitiator, at two different temperatures in an isotropic phase. To elucidate the factors determining the morphology of the obtained polymer (poly(A6OBA)), we chose two irradiation temperatures: one in the LC temperature range of the polymer, the other in the isotropic range. We investigated structures of the polymers by optical microscopy and scanning electron microscopy. SEM images showed that the film obtained at the lower temperature consisted of randomly extended fibers having a diameter of ca. 1.0 μm and some branches, whereas the film prepared at the higher temperature was composed of polymer particles with a diameter ca. 1.5 μm. By comparing these results with those of an earlier experiment in which we obtained macroscopically oriented LC fibers by photopolymerization under the LC phase of the blend, we infer the following; (i) the presence of an LC phase in the resulting polymer itself during photopolymerization is necessary for it to form fibrous morphology and (ii) the LC ordering field present prior to photopolymerization is not indispensable for the fibrous morphology but it is for the macroscopic orientation and reduction of the branches in the fibers.     

Solubilization of single-walled carbon nanotubes by entanglements between them and hyperbranched phenolic polymer

Hyperbranched phenolic polymer (HBP) was prepared by Lewis acid-catalyzed polycondensation of bifunctional phenolic monomer with trifunctional phenolic monomer. By choosing an appropriate Lewis acid, HBP was successfully obtained. By using physical adsorption of HBP on a single-walled carbon nanotube (SWCNT) surface, solubilization of SWCNTs was examined. SWCNTs were soluble with extended branches of HBP in N,N-dimethylformamide (DMF) solution, while they were insoluble in a linear phenolic polymer. In the presence of shrinking branches of HBP in tetrahydrofuran, SWCNTs were hardly soluble. Entanglements between extended branches of HBP and SWCNT in DMF solution resulted in high solubility of SWCNTs.     

Synthesis and photo-induced transformation of helical aromatic polyamides consisting of axially dissymmetric biphenylene joints and azobenzene segments in the backbone

Wholly aromatic polyamides having a novel helical structure were prepared by the reaction of axially dissymmetric (R)- or (S)-6,6′-dimethylbiphenyl-2,2′-dicarbonyl chloride with aromatic diamines, which are soluble in common solvents such as tetrahydrofuran and N,N-dimethylformamide. Photo-irradiation of a tetrahydrofuran solution of the polymer obtained with 4,4′-diaminoazobenzene induced a change of the helical conformation because of the trans–cis isomerization of the azobenzene units in the polymer chain. No change in the specific rotation of the polymer was observed on heating at 100°C for 4h, indicating thermal stability of its helical structure. CD spectra showed that the helical conformation was maintained in methanesulphonic acid. © 1998 SCI.     

Behavior of interfacial polycondensation on synthesizing of poly(amic ester)s

The behavior in interfacial polycondensation of 4,4′-methylenedianiline or 4,4′-oxydianiline (ODA) in water with dimethoxycarbonyl terephthaloyl chloride (DCMTC) in dichloromethane with benzyltriethylammonium chloride (BTEAC) as a catalyst was examined with a Fourier transform infrared spectrophotometer, attenuated total reflectance, an ultraviolet spectrophotometer, and a scanning electron microscope. When the ratio of the DCMTC concentration to the ODA concentration was about 2: 1, the interfacial polymer obtained had relatively high inherent viscosity. With the addition of a suitable amount of sodium carbonate and BTEAC, the interfacial polymer obtained had relatively high inherent viscosity. The polymer film grew toward the organic phase from the interface region until the reaction was over. The surfaces of the films adjacent to the water phase were composed of the polymer having a higher molecular weight and were denser in morphology than those of the films adjacent to the organic phase. © 1996 John Wiley & Sons, Inc.     

Radiation protection of poly(vinyl chloride) by N,N-dialkyl dithiocarbamate substitution

The effect of N,N-dialkyl dithiocarbamate substitution on the radiation stability of poly(vinyl chloride) (PVC) film was studied. PVC containing 6.5–15.7 mole-% N,N-dimethyl dithiocarbamate (PDM) and PVC containing 8.3–17.5 mole-% N,N-diethyl dithiocarbamate (PDE) was irradiated with γ-rays from a Co-60 source at room temperature under vacuum. The evolved gaseous products were measured and analyzed with a mass spectrometer. The apparent G values for gas evolution of PDM and PDE decreased remarkably. For example, a G value of 0.10 was obtained for a PDE which contains 17.5 mole-% diethyl dithiocarbamate group. The mass spectrum of the evolved gas from the same PDE sample with 10-Mrad irradiation showed no hydrogen chloride to be present. The external protection was studied using polymer-blended films of PVC and PDE or PDM. The stabilization coefficients for internal protection and external protection in polymer blends were calculated. Although the ESR spectrum of the irradiated PDM, PDE, and PVDE which is synthesized by polymerization of S-vinyl-N,N-diethyl dithiocarbamate (VDE) showed the same sulfur radicals, they were different from those of the irradiated cysteamine hydrochloride and PVC containing N-methyl dithiocarbamate (PMD). From these results, the protection of a polymer by a covalently bound dithiocarbamate was discussed.     

Synthesis and properties of novel soluble fluorinated aromatic polyamides containing 4-benzoyl-2,3,5,6-tetrafluorophenoxy pendant groups

A new diaroyl chloride monomer, 5-(4-benzoyl-2,3,5,6-tetrafluorophenoxy)isophthaloyl dichloride (BTFPIPC), was prepared in a three-step synthesis. Six novel aromatic polyamides containing 4-benzoyl-2,3,5,6-tetrafluorophenoxy pendant groups were synthesized by low temperature polycondensation of BTFPIPC with six aromatic diamines in N,N-dimethylacetamide (DMAc). All these new polymers are amorphous and readily soluble in various dipolar solvents such as DMAc, N-methyl-2-pyrrolidinone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) at room temperature. These polymers showed glass transition temperatures between 212 and 243 °C and 5% weight loss temperatures ranging from 439 °C to 456 °C. These polyamides could be cast into transparent, flexible and strong films from DMAc solution with tensile strengths of 73.5–85.4 MPa, tensile moduli of 2.06–2.72 GPa, and elongations at break of 6.4–9.3%. These new polyamide films exhibited low dielectric constants of 3.26–3.57 (1 MHz), lower water uptakes in the range of 1.27–2.28%, and excellent transparency with an ultraviolet-visible absorption cut-off wavelength in the 326–373 nm range. Primary characterization of these new polyamides shows that they might serve as new candidates for processable high-performance polymeric materials.     

Synthesis and properties of some aromatic polyamides with coumarin chromophores

A novel monomer diacid, 6,6′-methylenebis{2-oxo-8-{2-[(2-oxo-2H-chromen-7-yl)oxy]acetoxy}-2H-chromene-3-carboxylic acid}, having two substituents (2-oxo-2H-chromen-7-yl)oxyacetate in the aromatic moiety, was synthesized and used in a direct polycondensation reaction with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents to give a series of new aromatic polyamides with photosensitive coumarin pendent groups. Polyamide properties were investigated by DSC, TGA, GPC (gel permeation chromatographic analysis), and wide-angle X-ray scattering, viscosity and solubility measurements. The introduction of bulky side chains in the structure of aromatic polyamides led to moderate inherent viscosity values (0.40–0.87 dLg^?1) and increased solubility of these polymers in aprotic polar solvents such as NMP (N-methylpyrrolidone), DMAc, DMSO and DMF, and in less polar solvents like Py and THF. The good solubility of these polyamides was in agreement with their amorphous character as evidenced by X-ray diffraction diagrams. Gel permeation chromatography evidenced high molecular weights (49,400–63,900 gmol^?1) which allowed transparent, flexible and tough films to be cast from polymer solutions. These aromatic copolyamides showed good thermal properties associated with glass transition temperatures (Tg) in the range of 221–257 °C and the onset of decomposition in air above 390 °C. UV illumination (λ > 300 nm) of the polymer films induced crosslinking between polyamide molecules through a [2π + 2π] photocycloaddition at the CC bond of coumarin moieties. Information concerning the photoreactive property of coumarin-containing polymers was obtained by studying the changes in the UV absorption spectra and IR spectra of irradiated polymeric films.     

Effects of composition and plastifier on the light scattering of polymer glasses and properties of polymeric optical fibers made from styrene-methyl methacrylate copolymers

High optical purity polystyrene (PS), poly(methyl methacrylate) (PMMA) and styrene-methyl methacrylate statistical copolymers (S-MMA) were prepared. Light scattering measured on polymeric glasses depends on the chemical composition of the polymer and on the refractive index of the plastifier added. An isorefractive plastifier reduces considerably the scattering values for the copolymers S-MMA, while having no significant effect on the scattering of PMMA. A plastifier with a refractive index different from that of the polymer raises distinctly the light scattering values in all cases. It has been shown that the isorefractive plastifier has a favourable effect on attenuation loss of polymeric optical fibers (POF) obtained from the copolymer S-MMA 2/1.     

Ionic graft copolymerization. VI. Graft copolymerization of β-propiolactone and N-vinylcarbazole onto trunk polymer containing carboxylic acid,sulfonic acid,and their salts

It was pointed out in previous papers that both cationic and anionic polymerization might be involved simultaneously in grafting onto trunk polymers containing ? COOH or ? SO₃Na. The graft copolymerization of β-Propiolactone (βPL)–N-vinylcarbazole (NVCZ) onto styrene-divinylbenzene copolymers containing carboxylic acid, sulfonic acid, and their salts was carried out in order to distinguish between the polymers produced by anionic and cationic mechanisms. The polymer obtained by the polymerization of βPL–NVCZ with BF₃·OEt₂, a typical cationic catalyst, consisted mainly of NVCZ units, but the polymer obtained with BuLi, a typical anionic catalyst, consisted mainly of βPL units. In the graft copolymerization of NVCZ–βPL onto trunk polymer containing ? COOH, the NVCZ contents of the branch polymer and the tolueneinsoluble fraction were estimated to be ca. 50 mole-%; therefore these polymers were produced by both cationic and anionic mechanisms. In the case of graft copolymerization onto the trunk polymer containing SO₃Na, it was found that both cationic and anionic polymerization also occurred simultaneously.