No abstract

A new class of liquid‐crystalline epoxy resins containing azomethine and azo groups was synthesized and structurally characterized. The liquid crystal behavior of these compounds was characterized by differential scanning calorimetry (DSC), hot‐stage polarized optical microscopy (POM) and wide‐angle X‐Ray diffraction (WAXS). An aliphatic spacer between the mesogenic aromatic central core and the glycidyl groups favors the formation of different types of smectic mesophases with a wide range of stability. The LC resins were cured to obtain liquid crystal thermosets (LCTs). The cure was tested using aromatic primary diamines as curing agents and nematic‐like networks were obtained. When tertiary amines were used catalytically, smectic C‐like networks were retained when the spacer length had four methylene units or more. The polydomain ordered materials obtained were characterized by WAXS and their thermal stability was tested by thermogravimetric analysis (TGA).

No abstract

The effect of-irradiation on the structure and composition of chemically synthesized few-layered graphene materials was studied. Fully oxidized graphene oxide and graphene nanoribbons, as well as their respective chemically post-reduced forms, were treated under-irradiation in an air-sealed environment. Three different irradiation doses of 60, 90 and 150 kGy were applied. Structure and composition of the irradiated materials were analyzed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Raman spectroscopy and Xray photoelectron spectroscopy (XPS). The XRD patterns were not affected byirradiation, and small changes were observed in the FTIR and TGA results. However, significant modifications were detected by Raman spectroscopy and XPS, particularly in the Raman G/D band intensity ratios and in the C 1s XPS profiles. Comparatively, the changes in Raman and XPS spectra after-irradiation were even greater than those occurring during the chemical reduction of graphene oxides. Our results indicate that the graphene carbon lattice was strongly affected by-irradiation, but the materials experienced small variations in their oxygen content.

We report a new strategy to obtain high performance polymer-grafted multi-walled carbon nanotubes (MWCNTs). Chlorophenyl-functionalized MWCNTs, obtained through the in situ generation and reaction of diazonium compounds, were subjected to polymerization in the presence of Na 2 S and 1,4dichlorobenzene in order to yield MWCNTs covalently functionalized with poly(p-phenylene sulfide) (PPS) oligomers. The MWCNT functionalization and the PPS oligomeric chain growth can be controlled throughout accessible experimental variables, including the possibility to carry out the whole process in a one-pot reaction. This represents an efficient and facile route to develop covalently grafted MWCNTs beyond those reported so far for the same polymer. These materials are promising fillers for the production of high performance PPS-based composite materials, due to the improvement of the filler-matrix compatibility. The manufacturing and characterization of some test samples show that oligomer-grafted MWCNTs induce the suppression of the intrinsic confinement effect imposed by the nanofiller, as for the observation of an increase in the PPS crystallinity. An outstanding increase in the PPS thermal stability and mechanical properties is also observed, as compared to bare MWCNTs, while leaving the electrical properties unharmed.