Silver Nanowires Coated Nitrocellulose Paper for High-Efficiency Electromagnetic Interference Shielding

A thin and conductive coating on an environmentally friendly polymer is imperative for protecting sensitive electronic devices. In this regard, a series of silver nanowires (AgNWs) coated nitrocellulose (NC) papers are fabricated by a simple and fast processed vacuum-assisted filtration method by varying filtrate volume to address electromagnetic interference. Their structural and EMI shielding performance is analyzed. The submicron thick and the lighter paper reveal the conductive AgNWs interwoven on the rough NC surface, making a 2D in-planar structure. Due to a strongly interconnected network, the coated paper displays an exceptional electrical conductivity of 8603 S/m. Despite having a minimum AgNW coating thickness of ∼0.69 μm and an area density of 0.041 mg/cm², an ultrahigh EMI shielding effectiveness (SE) of about 69.4 dB (a specific EMI SE (SE/t) of 1005797 dB/cm) in the entire X-band (8-12 GHz) region is achieved. The effective material parameters, extracted using plane-wave theory, indicate that AgNWs form closed current loops resulting in magnetic losses. These AgNWs coated NC papers synthesized by a simple procedure are promising EMI shielding materials for current emerging electronic devices.

Metal Complexes of the Porphyrin-Functionalized Polybenzoxazine

New porphyrin-functionalized benzoxazine (Por-BZ) in high purity and yield was synthesized in this study based on ¹H and ¹³C NMR and FTIR spectroscopic analyses through the reduction of Schiff base formed from tetrakis(4-aminophenyl)porphyrin (TAPP) and salicylaldehyde and the subsequent reaction with CH₂O. Thermal properties of the product formed through ring-opening polymerization (ROP) of Por-BZ were measured using DSC, TGA and FTIR spectroscopy. Because of the rigid structure of the porphyrin moiety appended to the benzoxazine unit, the temperature required for ROP (314 °C) was higher than the typical Pa-type benzoxazine monomer (ca. 260 °C); furthermore, poly(Por-BZ) possessed a high thermal decomposition temperature (T_d10 = 478 °C) and char yield (66 wt%) after thermal polymerization at 240 °C. An investigation of the thermal and luminescence properties of metal–porphyrin complexes revealed that the insertion of Ni and Zn ions decreased the thermal ROP temperatures of the Por-BZ/Ni and Por-BZ/Zn complexes significantly, to 241 and 231 °C, respectively. The metal ions acted as the effective promoter and catalyst for the thermal polymerization of the Por-BZ monomer, and also improved the thermal stabilities after thermal polymerization.