Effect of polydopamine coating on improving photostability of poly(1,3,4-oxadiazole)s fiber

Effect of polydopamine coating on improving photostability of poly(1,3,4-oxadiazole)s (POD) fiber was studied in detail. Due to strong adhesion ability of polydopamine, the POD fiber could be coated easily by dopamine in Tris–HCl (pH?=?8.5) solution at room temperature with exist of oxygen. The polydopamine coating was characterized by SEM, XPS and ATR-FTIR. It was proved by UV-spectra analysis that the polydopamine coating had a strong absorbance in ultraviolet wavelength and was very stable to ultraviolet. Additionally, it was found by pyrogallol autoxidation method that the polydopamine could efficiently capture superoxide anion radical, which was an important factor that resulted in photodegradation of POD fiber, due to its catechol structure. These two findings implied that polydopamine coating was a potential photoprotection agent. Finally, compared to POD fiber, the tensile test of POD fiber coated by polydopamine further proved that the polydopamine did improve the photostability of POD fiber. And the FTIR analysis of POD coated by polydopamine also confirmed that there was almost no macromolecular change after UV exposure.     

New polyhydrazides and poly(1,3,4-oxadiazole)s containing pendent phenoxy groups

A series of new polyhydrazides containing pendent phenoxy groups has been synthesized by low-temperature solution polycondensation of equimolar amounts of diacid dichlorides and 2-phenoxyterephthalic dihydrazide in N-methyl-2-pyrrolidi-none (NMP). The thermal cyclization of the polyhydrazides gave the corresponding poly(1,3,4-oxadiazole)s containing pendent phenoxy groups. The polymers were characterized by viscometry, solubility measurements, IR spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis.     

Preparation and characterization of ordered thin films based on aromatic poly(1,3,4-oxadiazole)s

Ultrathin layers of aromatic polyoxadiazoles by using the Langmuir-Blodgett technique are prepared for the first time. The syntheses and characterization of new soluble aromatic poly(1,3,4-oxadiazole)s are described. The polyoxadiazoles contain tetraphenyl silane units in the main chain or pendent alkylamido groups. Both the precursor route via polyhydrazide followed by thermal cyclization in bulk, and the direct spreading of poly(1,3,4-oxadiazole)s are used for film forming. The supramolecular structures of all ordered poly(arylene-1,3,4-oxadiazole) LB films are characterized by FTIR spectroscopy, X-ray scattering and atomic force microscopy, respectively.     

Synthesis and characterization of new poly(arylene ether 1,3,4-oxadiazole)s based on dihydroxynaphthalene isomers

Summary A series of new poly(arylene ether 1,3,4-oxadiazole)s has been obtained starting from a difluorosubstituted monomer containing 1,3,4-oxadiazole rings and some dihydroxynaphthalene isomers. The polymers have been prepared by polycondensation in solution and have been obtained in quantitative yield. They had inherent viscosity from 0.2 to 0.82 dL/g, showed good thermal stability (10% weight loss temperatures in nitrogen and air were above 460 and 450°C, respectively) and high glass transition temperatures (in the range of 197–232°C). The polymers were characterized by elemental and infrared analyses, GPC and wide angle X-ray diffraction. Received: 27 June 2000/Revised version: 2 October 2000/Accepted: 2 October 2000     

X-ray investigations on annealed fibers of poly(p-phenylene-1,3,4-oxadiazole)

The influence of annealing on the supermolecular structure of commercial, thermostable fibers, spun from solutions of poly(p-phenylene-1,3,4-oxadiazole) (POD) in H₂SO₄, is examined. The crystalline α-modification of thermally treated POD fibers has an orthorhombic unit–cell probably of space group P2₁2₁2₁. The symmetry of the single POD chain in these crystallites is 2₁. The unit–cell dimensions are a = 1.235 nm, b = 0.655 nm, c = 1.40···1.47 nm, where c depends on the annealing temperature T_a. The unit cell contains 4 chains of two monomers each. Annealing up to T_a of about 755 K causes increases in crystallite size, crystalline orientation, and linear degree of order, combined with an improved axial Young's modulus E. Thermal degradation at higher temperatures leads to the breaking of tie molecules in general, while UV-radiation selectively damages tie molecules that are not taut.     

Aromatic poly(1,4-phenylene-1,3,4-oxadiazole) fibers by dry jet-wet spinning

Fibers of poly(1,4-phenylene-1,3,4-oxadiazole) have been prepared by dry jet-wet spinning sulfuric acid solutions of the polymer. Polymer was prepared by polymerizing terephthalic acid and hydrazine dihydrochloride in 30% fuming sulfuric acid and directly spinning the resulting solution. Dry jet-wet spinning allows greater flexibility in conditions than does wet spinning in that spinneret temperature and coagulation bath temperature are independent of one another. Therefore, coagulation may be at temperatures well below those needed at the spinneret to maintain a flowing, extrudable solution. Another common advantage of dry jet-wet spinning is application of draw to the extruded fiber before coagulation, but in this system, drawing the fiber before coagulation was shown to be a disadvantage. Fiber properties were maximized by spinning with a spinneret temperature of 58–73°C into a coagulation bath at 3–4°C and with an air gap of 1/4 in. Water as a coagulation medium allowed operation at speeds up to 40 m/min, while with 50% sulfuric acid less than half that speed was reached. Application of draw ratios of 3/1 on the coagulated but still swollen fiber combined with high-temperature treatments at low draw ratios (1.05/l) gave maximum fiber properties–tenacity 6 g/denier, elongation 20–25%, and modulus 200–240 g/denier.     

New fluorinated poly(1,3,4-oxadiazole-ether-imide)s

New fluorinated poly(1,3,4-oxadiazole-ether-imide)s have been prepared by solution polycondensation reaction of different aromatic diamines having preformed 1,3,4-oxadiazole ring, such as 2,5-bis(p-aminophenyl)-1,3,4-oxadiazole, 2,5-bis[p-(4-aminophenoxy)phenyl]-1,3,4-oxadiazole, 2,5-bis[p-(3-aminophenoxy)phenyl]-1,3,4-oxadiazole, 2-(4-dimethylaminophenyl)-5-(3,5-diaminophenyl)-1,3,4-oxadiazole and 2-(4-fluorophenyl)-5-(3,5-diaminophenyl)-1,3,4-oxadiazole, with an aromatic dianhydride incorporating ether linkages and hexafluoroisopropylidene group, namely 1,1,1,3,3,3-hexafluoro-2,2-bis-[(3,4-dicarboxyphenoxy)phenyl]-propane dianhydride. The polymers were easily soluble in polar organic solvents, such as N-methylpyrrolidinone, N,N-dimethylformamide, and pyridine, as well as in certain low boiling-point organic solvents, such as tetrahydrofuran and chloroform. Very thin coatings deposited onto silicon wafers exhibited smooth, pinhole-free surface in atomic force microscopy. The polymers showed high thermal stability with decomposition temperature being above 410 °C. They exhibited a glass transition in the temperature range of 183-217 °C, with reasonable interval between glass transition and decomposition temperature. Solutions of some polymers in N,N-dimethylformamide exhibited blue fluorescence, having maximum emission wavelength in the range of 411-424 nm.     

聚(芳基醚1,3,4-噁二唑)类聚合物的磺化及表征

为了探索影响芳香族聚噁二唑的磺化反应的因素,分别以发烟硫酸和氯磺酸为磺化试剂对几种含醚键聚芳噁二唑(PEODs)进行磺化,研究了以氯磺酸为磺化试剂时磺化反应时间、用量对磺化反应的影响,并分析了PEODs用于质子交换膜的潜在应用.磺化产物的结构与性能通过傅里叶红外(FT-IR)、氢谱(1H-NMR)、离子交换当量、热重分析(TGA)和溶解性等测试进行了表征.结果表明:发烟硫酸磺化产物磺化度不可控制,磺化度较氯磺酸的磺化产物高;采用氯磺酸磺化时,磺化时间对磺化反应没有影响,氯磺酸用量仅对侧苯基双酚A型聚噁二唑有影响;邻叔丁基型聚噁二唑的氯磺酸磺化产物有用于质子交换膜的潜力.     

Synthesis,characterization, and thermal stability of novel wholly para-oriented aromatic poly(ether-amide-hydrazide)s bearing pendant groups and their corresponding poly(ether-amide-1,3,4-oxadiazole)s

Four novel wholly para-oriented aromatic poly(ether-amide-hydrazide)s containing various pendant groups on their aromatic rings were synthesized from p-aminosalicylic acid hydrazide (PASH) with an equimolar amount of either 4,4′-(1,4-phenylenedioxy)dibenzoyl chloride (1a), 4,4′-(2,5-tolylenedioxy)dibenzoyl chloride (1b), 4,4′-(2-tert-butyl-1,4-phenylenedioxy)dibenzoyl chloride (1c), or 4,4′-(2,5-biphenylenedioxy)dibenzoyl chloride (1d) via a low temperature solution polycondensation reaction. A polyamide-hydrazide without the ether and pendant groups, poly[4-(terephthaloylamino)salicylic acid hydrazide, PTASH, is also investigated for comparison. It was synthesized from PASH and terephthaloyl chloride by the same synthetic route. The polymer intrinsic viscosities ranged from 4.5 to 2.47 dlg⁻¹ in N,N-dimethyl acetamide (DMAc) at 30 °C and decreased with the introduction of the ether and pendant groups into the polymer. All the polymers were soluble in DMAc, N,N-dimethyl formamide (DMF), and N-methyl-2-pyrrolidone (NMP) and their solutions could be cast into flexible films with good mechanical strengths. Further, they exhibited a great affinity to water sorption. Their solubility and hydrophilicity increased with introduction of the ether and pendant groups into the polymer. The prepared polymers could be thermally cyclodehydrated under nitrogen atmosphere into the corresponding poly(ether-amide-1,3,4-oxadiazole)s approximately in the region of 300–450 °C. The introduction of the flexibilizing ether linkages and the pendant groups into the polymer improves the solubility of the resulting poly(ether-amide-1,3,4-oxadiazole)s compared to poly(amide-1,3,4-oxadiazole) free from these groups.     

Synthesis and characterization of new optically active poly(amide-imide)s containing 1,3,4-oxadiazole moiety in the main chain

Six new optically active poly(amide-imide)s were synthesized by poly condensation reaction of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (8) with six chiral N,N′-(bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic)-bis-l-amino acids (3a–f) in a medium consisting of N-methyl-2-pyrrolidone (NMP), triphenylphosphite (TPP), calcium chloride (CaCl₂), and pyridine. Chiral N,N′-(bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic)-bis-l-amino acids (3a–f) were obtained by the reaction of bicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (1) with two equimolar of l-alanine (2a), l-valine (2b), l-leucine (2c), l-isoleucine (2d), l-phenyl alanine (2e), and l-2-aminobutyric acid (2f) in acetic acid. The poly condensation reaction produced a series of novel poly(amide-imide)s (9a–f) in high yield and with inherent viscosities between 0.30 and 0.52 dL/g. The resulting polymers were characterized by elemental analysis, viscosity measurement, solubility testing, thermo-gravimetric analysis (TGA), ¹H-NMR, and FT-IR techniques.     

Synthesis of poly[methyl(phenyl)silanediyl] containing 1,3,4-oxadiazole electron-transporting moieties

Summary The new oxadiazole derivative containing amino group, 2-(4-aminophenyl)-5-(biphenyl-4-y1)- 1,3,4-oxadiazole (Oxad-NH₂), was synthesized and attached to formylated poly[methyl(phenyl)silanediyl] (PMPSi) by acid-catalyzed condensation of the aldehyde with the amino group yielding a Schiff base. The aldehyde groups were incorporated into the parent PMPSi by the reaction with dichloromethyl methyl ether in the presence of Lewis acid (SnCl₄). GPC analyses before and after modification reaction revealed that the attachment of Oxad-NH₂ proceeded without degradation of the silicon backbone. We reached 75 % conversion of aldehyde groups to oxadiazole Schiff base. The condensation reaction was followed and the prepared compounds and polymers were characterized by ¹H NMR, UV-vis, FT IR, GPC and elemental analyses. Fluorescence behavior of oxadiazole-modified PMPSi was studied in tetrahydrofuran. Broad emission band with maximum at 440 nm was observed. Fluorescence quantum yield of modified polysilanes increases with the increasing content of the attached oxadiazole moiety. Received: 10 February 2003/Revised version: 8 April 2003/Accepted: 8 April 2003 Correspondence to Drahomír Vyprachticky     

Metalphthalocyanines Anchored Poly(1,3,4-oxadiazole arylene ether)s: Optical and Electrical Studies

New phenolphthalein based poly(1,3,4-oxadiazole aryl ether) (PHOP) containing side chain carboxylic acid groups derived from 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and 2-(bis(4-hydroxyphenyl)methyl)benzoic acid have been synthesized from typical aromatic nucleophilic substitution reaction. The PHOP seizes high dielectric constant (300 at 50 Hz) by the assistance of polar pendants and its findness in advance studies needs some structure modification with high dielectric constant metalphthalocyanine (MPc, M=Co, Ni & Cu) macrocycle to come out as further enhancement of dielectric constant and become photoactive polymer embedded metalphthalocyanine (PPEMP1–9). The molecular weight of PHOP was determined by gel permeation chromatography and is found to be 33375 (M _w/M _n = 2.48). All the tailor-made polymers were well characterized by Solid State UV–Vis, thermogravimetric analysis and XRD analysis. FTIR and NMR spectroscopic techniques confirms MPc units are grafted into the polymer matrix and act as a utmost light catching materials in the visible to near IR region (400–900 nm) with remarkable drop off in optical band gap and exhibited impressive thermal properties. The variation in the AC conductivity was explained by electron hopping model and values are in the range of 3.16 × 10^?5–4.78 × 10^?5 (S/m) at 5 MHz measured at 20 °C.     

Metallo-homopolymer and metallo-copolymers containing light-emitting poly(fluorene/ethynylene/(terpyridyl)zinc(II)) backbones and 1,3,4-oxadiazole (OXD) pendants

A series of novel metallo-polymers containing light-emitting poly(fluorene/ethynylene/(terpyridyl)zinc(II)) backbones and electron-transporting 1,3,4-oxadiazole (OXD) pendants (attached to the C-9 position of fluorene by long alkyl spacers) were synthesized by self-assembled reactions. The integrated ratios of ¹H NMR spectra reveal a facile result to distinguish the well-defined main-chain metallo-polymeric structures which were constructed by different monomer ligand systems (i.e. single, double, and triple monomer ligands with various pendants). Furthermore, UV-vis and photoluminescence (PL) spectral titration experiments were carried out to verify the metallo-polymeric structures by varying the molar ratios of zinc(II) ions to monomers. As a result, the enhancement of thermal stability (T_d) and quantum yields were introduced by the metallo-polymerization, and their physical properties were mainly affected by the nature of the pendants. The photophysical properties of these metallo-polymers exhibited blue PL emissions (around 418 nm) with quantum yields of 34-53% (in DMF). In contrast to metallo-polymers containing alkyl pendants, the quantum yields were greatly enhanced by introducing 1,3,4-OXD pendants but reduced by carbazole (CAZ) pendants. Moreover, electroluminescent (EL) devices with these light-emitting metallo-polymers as emitters showed green EL emissions (around 550 nm) with turn-on voltages of 6.0-6.5 V, maximum efficiencies of 1.05-1.35 cd A⁻¹ (at 100 mA/cm⁻²), and maximum luminances of 2313-3550 cd/m² (around 15 V), respectively.     

Heterogeneity of poly-p-phenylene-1,3,4-oxadiazole solutions

Conclusions The heterogeneity of spinning dopes is mainly caused by impurities contained in the starting raw materials.Heterogeneity of concentrated POD solutions (above 13%) is connected with the formation of crystal solvates.The melting points of the crystal solvates in POD solutions dependls on the polymer content of the solution, the molecular weight of the POD, the sulfuric acid concentration, and the nature of the modifying components.Translated from Khimicheskie Volokna, No. 3, pp. 26–28, May–June, 1986.     

2,5-双去氢枞基-1,3,4-噻二唑和2,5-双去氢枞基-1,3,4-(噁)二唑的合成

以去氢枞酸为原料,经PCl3或SOCl2酰化得到去氢枞酰氯,与水合肼进行酰肼化反应得到N,N-二去氢枞酰基肼,再分别经过闭环和缩合反应得到目标化合物。研究了各化合物的反应条件;其中N,N-二去氢枞酰基肼的合成可在室温下完成,收率86.2%;合成2,5-双去氢枞基-1,3,4-噻二唑的最佳闭环剂是POCl3,在POCl3既做闭环剂又做溶剂的条件下,收率83.2%;2,5-双去氢枞基-1,3,4-噁二唑的合成中,在P2S5的作用下,以吡啶作为溶剂,收率可达到85.5%;整个合成路线中各步反应的收率都在80%以上,高收率得到目标化合物;其结构经IR、1HNMR和元素分析进行表征和确证。     

1,3,4-(噁)二唑类化合物杀菌活性研究进展

1,3,4-二唑类化合物因其独特的生物活性在农药、医药等领域受到广泛关注.将1,3,4-二唑环引入不同的化合物结构中,通过结构修饰能生成一系列具有广谱生物活性的化合物.它在新型农药创制中发挥越来越重要的作用.按照不同的结构进行分类,从杀菌方面对1,3,4-二唑类化合物的生物活性研究进展进行了综述,重点介绍了该类化合物的一些生物活性研究方面的工作,并对它的发展趋势和应用前景作了展望.     

Preparation and properties of polyphenylene-1,3,4-oxadiazole fibres

Copolymers of terephthalic and isophthalic acid (CPODZ) in 1:1 and 3:1 molar ratios with hydrazine sulphate and concentrated sulphuric acid were wet spun using water and H₂SO₄ coagulation baths. The filaments spun into water bath have inferior mechanical properties than those spun in H₂SO₄ bath. Physical properties, namely tenacity, elongation, modulus, resilience, elastic recovery, and dynamic mechanical properties were investigated. 1:1 CPODZ filaments showed higher strength, modulus and elasticity than 1:3 CPODZ filaments. These CPODZ fibres had a higher dynaic modulus and low loss tangent. The density and moisture regain of CPODZ filaments were also determined. The density of 1:1 CPODZ filaments was higher. The filaments spun in water bath had higher moisture regain. 1:1 CPODZ filaments had less regain compared to 1:3 CPODZ filaments.