Alkoxy-Substituted Poly(p-phenylene 1,3,4-oxadiazole)s:  Synthesis, Chemical Characterization, and Electro-Optical Properties

Abstract

The synthesis of a series of conjugated aromatic polyoxadiazoles (PODn) characterized by having moderate chain flexibility and highly flexible lateral substituents is reported. The majority of these polymers are soluble in a mixture of chloroform and trifluoroacetic acid and have inherent viscosities up to 0.9 dL/g. The glass transition temperature, T g , lies in the range 165-230 °C and depends on the side-chain length. The PODn show a good thermal stability in nitrogen up to 270 °C. Wide-angle X-ray diffractograms reveal a "comblike" organization of the polymeric chains. Homogeneous thin films of such a material were prepared by the spin-coating technique. Films spun on fused silica were characterized by spectroscopic analysis in the whole UV-vis-NIR range showing a high transmission in the NIR region which is the typical telecommunication band (1300-1500 nm). Furthermore, the refractive index and the film thickness have been measured using the coupled modes technique in a planar guiding structure having POD as the core. It has then been prepared a device consisting of the said polymer sandwiched between two electrodes on top of a glass substrate. The electron conductivity of the polymer has been found to be higher than that of terephthalic poly(1,3,4-oxadiazole).

Facile synthesis and characterization of poly(dialkoxy-p-phenylene 1,3,4-oxadiazole-alt-phenylene 1,3,4-oxadiazole)s

“…380 o C due to the decomposition of alkyl groups, as previously reported. 19 However, similar first weight loss was not observed for polyoxadiazoles, which were stable to 380 o C. Furthermore, para-polymers were observed somewhat more stable (higher T d ) than meta-polymers, which concurred the previous findings, 21 as thermal stability depends on adjacent monomer structures in order: ortho-ortho < meta-meta < meta-para < para-para.…”

“…26 o (2θ) observed for all the polymers, represented a d spacing of 3.4 Å. In terms of the layered packing model, this represents the distance between stacked polymer layers (layer thickness) in Figure 8 and agrees with previously reported results for poly(pphenylene 1,3,4-oxdiazole)s. 18,19 Moreover, this distance is identical to the typical distance observed between the aromatic planes in aromatic systems (e.g., graphite). The broad peak at ca.…”

“…M. Gillo et al previously described the layered structure of poly(phenylene oxadiazole), in which alkoxy side chains are arranged in planar extended conformations. 19 As shown in Figure 7, the powder diffractograms of all DPODs contained two sharp peaks and one broad diffraction peak. Using the formula n λ = 2 d sinθ (n : integer, λ : X-wavelength, d : spacing, θ : incident angle), we calcu- Polymers were dissolved in a co-solvent of chloroform and trifluoroacetic acid (2/1, v/v).…”

“…12,13,18,19 Polycondensation of dihydrazides and dichlorides occurred to afford the prepolymers, DPHZs, in DMAc/pyridine containing lithium chloride (5 wt%). Prepolymer cyclodehydration was performed at a high temperature (130 o C) using phosphorus oxychlo- ride.…”

Preparation and characterization of bismaleimide monomers with various structures

“…Much effort has been made to improve the mechanical and physical properties of polyaspartimides, e.g. to find new solutions systems and to modify their structures by introducing bulky substituents, incorporation of flexible linkages into the backbone, or by copolymerization [18,19].…”