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Nowadays, evolutions in wireless telecommunication industries, such as the emergence of complex 5G technology, occur together with massive development in portable electronics and wireless systems. This positive progress has come at the expense of significant electromagnetic interference (EMI) pollution, which requires the development of highly efficient shielding materials with low EM reflection. The manipulation of MXene surface functional groups and, subsequently, incorporation into engineered polymer matrices provide mechanisms to improve the electromechanical performance of conductive polymer composites (CPCs) and create a safe EM environment. Herein, Ti 3 C 2 T x MXene nanoflakes were first synthesized and then, taking advantage of their abundant surface functional groups, polyaniline (PA) nanofibers were grafted onto the MXene surface via oxidant-free oxidative polymerization at two different MXene to monomer ratios. The electrical conductivity, EMI shielding effectiveness (SE), and mechanical properties of poly (vinylidene fluoride) (PVDF)-based CPCs at different nanomaterial loadings were then thoroughly investigated. A very low percolation threshold of 1.8 vol % and outstanding electrical conductivities of 0.23, 0.195, and 0.17 S/cm were obtained at 6.9 vol % loading for PVDF−MXene, PVDF−MX 2 AN 1 , and PVDF−MX 1 AN 1 , respectively. Compared to the pristine MXene composite, surface modification significantly enhanced the EMI SE of the PVDF−MX 2 AN 1 and PVDF−MX 1 AN 1 composites by 19.6 and 32.7%, respectively. The remarkable EMI SE enhancement of the modified nanoflakes was attributed to (i) the intercalation of PA nanofibers between MXene layers, resulting in better nanoflake exfoliation, (ii) a large amount of dipole and interfacial polarization dissipation by constructing capacitor-like structures between nanoflakes and polymer chains, and (iii) augmented EMI attenuation via conducting PA nanofibers. The surface modification of the MXene nanoflakes also enhanced the interfacial interactions between PVDF chains and nanoflakes, which resulted in an improved Young's modulus of the PVDF matrix by about 67 and 46% at 6.9 vol % loading for PVDF−MX 2 AN 1 and PVDF−MX 1 AN 1 composites, respectively.

In this study, dual-layer polyamide 6/polyethersulfone (PA6/PES) composite membranes were prepared via the phase inversion technique and corona air plasma was employed to modify the membrane surface in order to improve the gas separation performance. The effect of corona treatment parameters like exposure time and input power on the membrane surface properties, morphology and separation performance was investigated. The gas separation performance of the membranes before and after the corona treatment was evaluated by permeation measurements for CO 2 , O 2 and N 2 gases. The FTIR-ATR, SEM, AFM and contact angle analyses were used to characterize the untreated and corona treated membranes. The FTIR-ATR and contact angle results indicated that the corona treatment introduced polar groups on the membrane surface and led to significant enhancement in the membrane polarity, hydrophilicity and wettability. The gas permeation results revealed that the permeability and selectivity of the modified membranes were changed dramatically due to surface ablation and formation of polar groups depending on the corona treatment conditions. An increase in corona treatment time and input power resulted in higher gas permeability, however corona modification at high power and longer exposure time led to a membrane with low gas selectivity.

No abstract

Transition-metal carbides (MXenes), multifunctional 2D materials, have caught the interest of researchers in the fabrication of high-performance nanocomposite membranes. However, several issues regarding MXenes still remain unresolved, including low ambient stability; facile restacking and agglomeration; and poor compatibility and processability. To address the aforementioned challenges, we proposed a facile, green, and cost-efficient approach for coating a stable layer of plant-derived polyphenol tannic acid (TA) on the surface of MXene (Ti 3 C 2 T x ) nanosheets. Then, high-performance reverse osmosis polyamide thin film nanocomposite (RO-PA-TFN) membranes were fabricated by the incorporation of modified MXene (Ti 3 C 2 T x −TA) nanosheets in the polyamide selective layer through interfacial polymerization. The strong negative charge and hydrophilic multifunctional properties of TA not only boosted the chemical compatibility between Ti 3 C 2 T x MXene nanosheets and the polyamide matrix to overcome the formation of nonselective voids but also generated a tight network with selective interfacial pathways for efficient monovalent salt rejection and water permeation. In comparison to the neat thin film composite membrane, the optimum TFN (Ti 3 C 2 T x −TA) membrane with a loading of 0.008 wt % nanofiller revealed a 1.4-fold enhancement in water permeability, a well-maintained high NaCl rejection rate of 96% in a dead-end process, and enhanced anti-fouling tendency. This research offers a facile way for the development of modified MXene nanosheets to be successfully integrated into the polyamide-selective layer to improve the performance and fouling resistance of TFN membranes.