Synthesis and properties of noncoplanar rigid‐rod aromatic polyhydrazides and poly(1,3,4‐oxadiazole)s containing phenyl or naphthyl substituents

Two new phenyl‐ and naphthyl‐substituted rigid‐rod aromatic dicarboxylic acid monomers, 2,2′‐diphenylbiphenyl‐4,4′‐dicarboxylic acid ( 4 ) and 2,2′‐di(1‐naphthyl)biphenyl‐4,4′‐dicarboxylic acid ( 5 ), were synthesized by the Suzuki coupling reaction of 2,2′‐diiodobiphenyl‐4,4′‐dicarboxylic acid dimethyl ester with benzeneboronic acid and naphthaleneboronic acid, respectively, followed by alkaline hydrolysis of the ester groups. Four new polyhydrazides were prepared from the dicarboxylic acids 4 and 5 with terephthalic dihydrazide (TPH) and isophthalic dihydrazide (IPH), respectively, via the Yamazaki phosphorylation reaction. These polyhydrazides were amorphous and readily soluble in many organic solvents. Differential scanning calorimetry (DSC) indicated that these hydrazide polymers had glass transition temperatures in the range of 187–234 °C and could be thermally cyclodehydrated into the corresponding oxadiazole polymers in the range of 300–400 °C. The resulting poly(1,3,4‐oxadiazole)s exhibited T_g's in the range of 252–283 °C, 10% weight‐loss temperature in excess of 470 °C, and char yield at 800 °C in nitrogen higher than 54%. These organo‐soluble polyhydrazides and poly(1,3,4‐oxadiazole)s exhibited UV–Vis absorption maximum at 262–296 and 264–342 nm in NMP solution, and their photoluminescence spectra showed maximum bands around 414–445 and 404–453 nm, respectively, with quantum yield up to 38%. The electron‐transporting properties were examined by electrochemical methods. Cyclic voltammograms of the poly(1,3,4‐oxadiazole) films cast onto an indium‐tin oxide (ITO)‐coated glass substrate exhibited reversible reduction redox with E_onset at ?1.37 to ?1.57 V versus Ag/AgCl in dry N,N‐dimethylformamide solution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6466–6483, 2006     

Poly(1,3,4-oxadiazole-amide)s containing pendent imide groups

A series of new poly(1,3,4-oxadiazole-amide)s containing pendent imide groups has been synthesized by solution polycondensation of aromatic diamines containing preformed 1,3,4-oxadiazole rings with two diacid chlorides containing imide rings. These polymers were also prepared by the reaction of the same diacid chlorides with p-aminobenzhydrazide which were subsequently cyclodehydrated in solid state. The polymers were soluble in polar amidic solvents and some of them gave transparent flexible films by casting from solutions. They showed high thermal stability with decomposition temperatures above 400°C and glass transition temperatures in the range of 245–327°C. They had low dielectric constants, in the range of 3.32–3.94, and good tensile properties.     

Dissolution of MWCNTs by using polyoxadiazoles,and highly effective reinforcement of their composite films

Nonmodified multiwalled carbon nanotubes (MWCNTs)/sulfonated polyoxadiazole (sPOD) nanocomposites are successfully prepared by a facile solution route. The pristine MWCNTs are dispersed in a sPOD solution, and the mixtures are fabricated into thin films by solution casting. The homogeneous dispersion of nanotubes in the composites is confirmed by transmission electron microscopy. The mechanical properties, thermal stability, and electrical conductivity are investigated. Tensile strength, elongation at break, and tensile energy to break are shown to increase by more than 28, 45, and 73%, respectively, by incorporating up to 1.0 wt % pristine MWCNTs. The experimental values for sPOD/MWCNTs composite stiffness are compared with Halpin‐Tsai and modified Halpin‐Tsai predictions. The storage modulus is found to increase up to 10% at low CNT loading. The composite films, which have an outstanding thermal stability, show an increase of up to 57 °C in the initial degradation temperature. The addition of 1.0 wt % MWCNTs increases the electrical conductivity of the sPOD matrix by two orders of magnitude. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A new class of aromatic poly-ether-aroyl-oxadiazoles. II. Studies on the cyclization reaction,infrared, structural,and morphological characterization

Poly-ether-aroyl-oxadiazoles (PEODZ) of general formula: are reported. Thermal cyclization of the starting polyhydrazides, infrared, thermal, and structural characterization are discussed as function of the number of methylene spacers in the range 2–12. It is found that the position of melting is strongly dependent upon the number of? CH₂? , and that moldable polyoxadiazoles are obtained at × values > 7. The spherulitic nature of PEODZ is clearly revealed by thermal-optical microscopy which, together with isothermal crystallizations at the differential scanning calorimeter, gives a close insight into the crystalline organization of such polymers. © 1994 John Wiley & Sons, Inc.     

Thermal and structural analysis and crystallization behavior of new poly(ether-alkyl) oxadiazoles

A new series of poly(ether-alkyl)oxadiazoles of general formula: with m = 3, 4, and 5 has been obtained from the corresponding polyhydrazides through thermal cyclization reaction. The polymers were characterized by infrared spectroscopy, differential scanning calorimetry, wide-angle x-ray analysis, and optical microscopy. The polymers were crystalline, with a crystalline texture and structural parameters strongly dependent on the value of m. The T_m's and T_g's value decreased with increasing number of CH₂. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of conjugated polymers and their blends for optoelectronic applications

Various polymeric blends of hole transporting materials, (such as MEH-PPV and P3HT) and electron transporting materials (such as poly(phenyl-vinyl-quinoline) and poly[2-(4-methacryloxyphenyl)-5-phenyl)-1,3,4-oxadiazole]) have been prepared and investigated. Moreover a soluble, main chain oxadiazole bearing polyether has been synthesized, aiming towards an efficient electron transporting polymeric material which was also used for blend preparation together with P3HT. A deeper investigation into their spectroscopic characteristics using, primarily, FT-IR spectroscopy, but also UV-Vis spectroscopy has been conducted. The surface morphology of these blends was investigated using Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) in an attempt to gather information for their solid state properties and morphologies. Finally, DSC measurements provided additional insight into the thermal behaviour of these materials.