A new AB 2 monomer, 2,3-bis(3-amino-4-hydroxyphenyl)quinoxaline-6-carboxylic acid dihydrochloride, was synthesized in four steps starting from the double condensation of commercially available 3,4diaminobenzoic acid and 4,4′-dimethoxybenzil. It underwent facile polycondensation in polyphosphoric acid to afford the corresponding hyperbranched quinoxaline-benzoxazole polymer (PPQ-BO 5) with an intrinsic viscosity of 1.04 dL/g. It was end-capped with 2-thiophenecarboxylic acid, 3,5-dihydroxybenzoic acid, 3-sulfobenzoic acid, 4-sulfobenzoic acid, and 2,3-diphenylquinoxaline-6-carboxylic acid. These hyperbranched polymers displayed an unusual, nonlinear solution viscosity behavior at the concentrations below ∼0.25 g/dL. At these dilute concentrations, both reduced and inherent viscosities decreased precipitously ("inverse polyelectrolyte behavior"). The large numbers of o-aminophenol end groups were further chemically modified to afford hyperbranched PPQ-BO's with various functionalities. Similar to their linear analogues, the T g 's of all chain-end-modified polymers were not detected up to 450 °C by DSC. PPQ-BO's had UV absorption maxima near 377 nm in basic NMP and 448 nm in MSA. Its emission maxima were at 467 nm in NMP and 475.5 and 767 nm in MSA.
SUMMARY: Rigid-rod benzobisthiazole (Bipy-PBZT), benzobisoxazole (Bipy-PBO) and benzobisimidazole (Bipy-PyBI) polymers containing 2,29-bipyridine-5,59-diyl moieties were synthesized from 2,29-bipyridine-5,59-dicarbonyl dichloride and one of the following monomers: 2,5-diamino-1,4-benzenedithiol, 4,6-diamino-1,3-benzenediol, and 2,3,5,6-tetraaminopyridine. Bipy-PyBI is the first rigid-rod benzobisimidazole polymer without any solubilizing pendants that exhibits lyotropic behavior. These polymers displayed thinfilm electrical conductivity of L10 -10 -10 -8 S/cm in pristine state; 10 -5 -10 -4 S/cm upon infiltration with AgNO 3 ; 25 -42 S/cm after Ag + e Ag 0 reduction by NaBH 4 .
ABSTRACT:As an alternative method for processing polyaniline (PANI) from its conducting (protonated) state, vacuum casting of PANI from a methanesulfonic acid (MSA) solution provided films with electrical conductivity values of about 130 -150 S/cm. In addition, we similarly prepared blended films of PANI ⅐ MSA and poly(p-phenylene benzobisthiazole) (PBZT). This process eliminated the need for a subsequent protonation step and had the additional advantage that the conjugated PBZT may provide alternative conducting pathways. Conductivity values of the composite films ranged from 100 pS/cm to 124 S/cm, and the films displayed critical concentration behavior with a PANI threshold concentration of 2.75% and a critical exponent of 4. Transmission electron micrographs displayed phase-separated regions with PANI forming a continuous network at high concentrations. Thermogravimetric analysis results demonstrated the thermal and thermooxidative stability advantage of the blends due to the PBZT component.
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