Optical, electrochemical, and thermal behavior of polybenzoxazine copolymers incorporated with tetraphenylimidazole and diphenylquinoline

Supercapacitor and high k properties of CNT-PbS reinforced quinoxaline amine based polybenzoxazine composites

The new 2,3-diphenylquinoxalin-6-amine (dpqa) was designed and synthesized through an efficient and high yield condensation process. Data from FTIR and ¹H-NMR spectroscopy have been adopted to ascertain the molecular structure of benzoxazine compounds. Furthermore, the quinoxaline amine based benzoxazine (BA-dpqa) was synthesized using bisphenol-A and paraformaldehyde followed by combining different weight percentages (1, 5 and 10 wt%) of (3-glycidyloxypropyl)trimethoxysilane functionalized CNT-PbS with benzoxazine to obtain nanocomposites. The thermal and morphological properties of the quinoxaline amine based neat polybenzoxazine matrix poly(BA-dpqa) and CNT-PbS/poly(BA-dpqa) composites were analysed by XRD, TGA and SEM analysis. The values of the degradation temperature (T_d) obtained for neat poly(BA-dpqa) and 10 wt% CNT-PbS/poly(BA-dpqa) composites are 414 °C and 424 °C. Furthermore, the chair yield percentage was calculated as 33% and 35% respectively. The water contact angle of polybenzoxazine gradually increased from 89° to 127° proportional to the content of CNT-PbS. Among the composites, 10 wt% CNT-PbS reinforced poly(BA-dpqa) nanocomposites possess higher dielectric constant (k = 11.0) than other composites. The pseudocapacitor nature of the prepared electrodes is demonstrated by the good electrochemical performance according to the CV curve. Also, the prepared 10 wt% CNT-PbS/poly(BA-dpqa) (637 F g^-1 at 5 A g^-1 and 11.8 Ω) electrode shows better capacitance and lower charge transfer resistance values than 5 wt% CNT-PbS/poly(BA-dpqa) (613 F g^-1 at 5 A g^-1 and 13.2 Ω) and neat poly(BA-dpqa) (105 F g^-1 at 5 A g^-1 and 15.6 Ω) according to the charge/discharge curves and EIS spectra. 10 wt% CNT-PbS/poly(BA-dpqa) shows 99.2% cycling efficiency even at the 2000th cycle, which indicates the good electrochemical performance of the prepared electrode.

In(NO3)3 catalyzed curing reaction of benzoxazine

Benzoxazine is a new kind of thermoset resin with excellent properties, but it suffers from high curing temperature and low char yield in the presence of catalyst without halogen. In(NO3)3 was herein used for the first time to efficiently catalyze the curing reaction of benzoxazine and to elevate the char yield at 800°C. The reaction of benzoxazine was catalyzed by In(NO3)3 after stirring at 35°C for 300 min, and the initial curing temperature decreased to 151°C. Polybenzoxazine/In(NO3)3 showed higher thermal stability and char yield at 800°C (increased by 7.5%) compared with those of polybenzoxazine. The possible pathway of coordination bonding between In3+ and benzoxazine was proposed. In the cross-linking process, two different structures, that is, the N, O-acetal bridge structure and arylamine Mannich bridge structure formed at 35°C, both existed, which ultimately affected the thermal stability of the cured product.