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 (Td) 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.

Silk Sericin-Polylactide Protein-Polymer Conjugates as Biodegradable Amphiphilic Materials and Their Application in Drug Release Systems.

Silk sericin (SS) is a byproduct of silk production. In order to transform it into value-added products, sericin can be used as a biodegradable and pH-responsive building block in drug delivery materials. To this end, amphiphilic substances were synthesized via the conjugation of hydrophobic polylactide (PLA) to the hydrophilic sericin using a bis-aryl hydrazone linker. PLA was esterified with a terephthalaldehydic acid to obtain aromatic aldehyde terminated PLA (PLA-CHO). In addition, lysine groups of SS were modified with the linker succinimidyl-6-hydrazino-nicotinamide (S-HyNic). Then, both macromolecules were mixed to form the amphipilic protein-polymer conjugate in buffer-DMF solution. The formation of bis-aryl hydrazone linkages was confirmed and quantified by UV-vis spectroscopy. SS-PLA conjugates self-assembled in water into spherical multicompartment micelles with a diameter of around 100 nm. Doxorubicin (DOX) was selected as a model drug for studying the pH-dependent drug release from SS-PLA nanoparticles. The release rate of the encapsulated drug was slower than that of the free drug and dependent on pH, faster at pH 5.0, and it resulted in a larger cumulative amount of drug released than at physiological pH of 7.4. The SS-PLA conjugate of high PLA branches showed smaller particle size and lower loading capacity than the one with low PLA branches. Both SS-PLA conjugates had negligible cytotoxicity, whereas after loading with DOX, the SS-PLA micelles were highly toxic for the human liver carcinoma immortalized cell line HepG2. Therefore, the SS-based biodegradable amphiphilic material showed great potential as a drug carrier for cancer therapy.

Morphology development and stability of polypropylene/organoclay nanocomposites.

A series of polypropylene (PP)/organoclay nanocomposites with varied concentrations of clay, from 1 to 7 wt%, was successfully prepared via melt intercalation using a PP functionalized with maleic anhydride as compatibilizer. The morphology/property relationships of the nanocomposites were investigated by XRD, TGA and DSC analyses. Two distinct groups of composites, from a quasi-exfoliated to an intercalated/flocculated morphology, were identified. In particular, intercalated/flocculated morphologies were obtained for those composites with an organoclay concentration beyond the threshold (3 wt%), as evidenced by XRD analysis and confirmed by the increase of the glass transition temperature. This last effect was related to the confinement of polymer chains between the silicate layers, generating a reduction of the chain mobility. The variable increase of the thermal stability of the nanocomposites was also likely related to the different degree of exfoliation/intercalation of the samples. The toluene extraction of composites was used as a powerful methodology to distinguish between polymer phases differently interacting with the inorganic surface: composites having a semi-exfoliated structure were split into two fractions having a similar morphology. For those samples having the higher organoclay concentration and intercalated morphology, a toluene-residue fraction was obtained containing almost all the clay present in the pristine composite. Furthermore, in this case the morphological analysis of the residue fraction evidenced a collapse of the inorganic structure compared to that of the unextracted composite. A careful characterization of both soluble and residue fractions is reported and the results are discussed considering the interactions at the interface between the functionalized PP chains and silicate layers and their effects on the organoclay dispersion degree and stability.

Development of biodegradable foamlike materials based on casein and sodium montmorillonite clay.

Biodegradable foamlike materials based on a naturally occurring polymer (casein protein) and sodium montmorillonite clay (Na+ -MMT) were produced through a simple freeze-drying process. By utilizing DL-glyceraldehyde (GC) as a chemical cross-linking agent, the structural integrity of these new aerogels were remarkably improved when compared to those of the control system (without GC), with a minimal increase in the density from 0.11 to 0.12 g cm⁻³. The degree of perfection of the foamlike structures was another parameter that had a significant influence on the physical and thermal performances of the low density composites. The biodegradability of the aerogels was investigated in terms of the carbon dioxide (CO2) evolution for up to 8 weeks in compost media under controlled conditions.