Development of quinoline-based heteroatom polybenzoxazines reinforced graphitic carbon nitride (GCN) carbonisation composites for emerging supercapacitor applications.

The current research described in this paper, focuses on the development of a new quinoline-based Mannich-type benzoxazine and its use to obtain advanced carbonisation materials with a high energy storage capacity. Based on this, a quinoline-based benzoxazine monomer (Q-xda) was synthesised by a reaction between 8-hydroxyquinoline, xylylenediamine and paraformaldehyde, and it is characterised by FT-IR and 1H-NMR spectroscopy. Composites were prepared from the benzoxazine and variable weight percentages of graphitic carbon nitride (GCN) (i.e., 5, 10, and 15 wt%). The oxazine ring-opening curing process of the polybenzoxazine composites, and its subsequent pyrolysis reaction was performed; and their chemical structures were confirmed using FT-IR spectroscopy. Also, the thermal and morphological characteristics of the composites were evaluated by XRD, thermogravimetric analysis (TGA), and SEM analyses. According to the results of the thermal experiments, adding GCN reinforcement significantly increased the thermal stability and char yield of the resultant composites. Electrochemical, and hydrophobic investigations were also carried out, and the results of these suggesting that the composites reinforced with 15 wt% GCN exhibit the highest dielectric constant (high κ = 10.2) and contact angle (145°). However, all the crosslinked composites demonstrated a remarkable electrochemical performance as pseudocapacitors. The resulting poly(Q-xda) + 15 wt% GCN electrodes showed a higher capacitance and a lower transferred charge resistance (i.e., 370 F g-1 at 6 A g-1 and 20.8 Ω) than the poly(Q-xda) electrode (i.e., 216 F g-1 at 6 A g-1 and 26.0 Ω). In addition, the poly(Q-xda) + 15% GCN exhibited a cycling efficiency of 96.2% even after 2000 cycles. From these results, it can be concluded that the constructed electrodes perform well in electrochemical operations.

Microparticles based on ionic and organosolv lignins for the controlled release of atrazine.

Lignins are natural polymers of the lignocellulosic biomass. Nowadays, there is a growing interest in developing value-added products based on lignins due to their renewability, low cost and abundance. In this work, lignin microspheres from organosolv and ionic isolation processes were prepared for the controlled release of atrazine. Microspheres were prepared by the solvent extraction/evaporation technique. The controlled release of atrazine from organosolv and ionic lignins microparticles was studied in water. Mobility experiments were performed in an agricultural soil from Argentina. The results showed that microparticles prepared using dichloromethane as the dispersed phase were spherical, while lignins dispersed in ethyl acetate produce irregular microparticles. Organosolv lignin microparticles presented higher encapsulation efficiency for all herbicide loads. About 98% and 95% of atrazine was released in 24 and 48 h approximately from organosolv and ionic lignin microparticles, respectively. The release profiles of atrazine from both lignin microparticles were not affected by the herbicide load. Atrazine mobility experiments in soil showed that about 80% of free atrazine was leached in 37 days, while 65.0% and 59.7% of the herbicide was leached from ionic and organosolv lignin microparticles, respectively. Thus, atrazine-loaded microparticles could reduce leaching compared to a commercial formulation of free atrazine.