A series of polyimides (PIs) based on ether-linked cyclohexyldiamine were prepared using pyromellitic dianhydride (PI-1), benzophenone dianhydride (PI-2), naphthalene dianhydride (PI-3), and perylene dianhydride (PI-4) in 1-methyl-2-pyrrolidone (NMP) medium to obtain respective polyamic acids and are subsequently converted into PIs through thermal imidization. The resulting PIs were characterized by Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and impedance analyses. In addition, the ultraviolet (UV) shielding ability of PIs was also studied and discussed. The vibrational analysis confirms the imidization, and the XRD profile indicates the amorphous nature of the resulting PIs. The PIs synthesized in the present work exhibit good solubility in organic solvents such as NMP, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). The PI-4-based imide possesses very good solubility with the highest glass transition temperature value of 256°C, highest char yield of 50.16%, highest dielectric constant of 3.9 and higher UV shielding performance of 89% than those of other PIs. Further, the good solubility also makes them useful for coating applications in aerospace and liquid crystal displays.
In the present work, different weight percentages (1, 3, and 5 wt%) of benzoxazine-functionalized graphene oxide (FGO) were reinforced with polybenzoxazine (PBZ) matrix by means of ring-opening polymerization. The resulting nanocomposites were characterized for their thermal, mechanical, dielectric, and optical properties using different analytical techniques. From the results of these studies, it was observed that the 5 wt% FGO-reinforced PBZ composite shows an improved glass transition temperature, thermal stability, and dielectric constant to the extent of 18%, 39%, and 197%, respectively, when compared with those of neat PBZ matrix. Furthermore, 5 wt% FGO-reinforced PBZ composite also exhibits an enhanced ultraviolet shielding efficiency (88%), with improved tensile strength (52%) compared with those of neat PBZ matrix. The enhanced properties may be due to homogeneous and uniform distribution of FGO into the PBZ matrix, which was confirmed from scanning electron microscopic and high-resolution transmission electron microscopic images. Data obtained from these studies indicate that the developed nanocomposites with high dielectric constant can be used in the form of coatings, sealants, and encapsulates for high-performance dielectric as well as antistatic applications.
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