Habibpour Saeed, Zarshenas Kiyoumars, Zhang Maiwen, Hamidinejad Mahdi, Ma Li, Park Chul B, Yu Aiping
Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo N2L 3G1, Canada.
Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo N2L 3G1, Canada.
ACS Appl Mater Interfaces. 2022 May 11;14(18):21521-21534. doi: 10.1021/acsami.2c03121. Epub 2022 Apr 28.
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, TiCT 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-MXAN, and PVDF-MXAN, respectively. Compared to the pristine MXene composite, surface modification significantly enhanced the EMI SE of the PVDF-MXAN and PVDF-MXAN 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-MXAN and PVDF-MXAN composites, respectively.
如今，无线通信行业的发展，如复杂的5G技术的出现，与便携式电子设备和无线系统的大规模发展同步进行。这一积极进展是以严重的电磁干扰（EMI）污染为代价的，这就需要开发具有低电磁反射的高效屏蔽材料。对MXene表面官能团的调控以及随后将其掺入工程聚合物基体中，为改善导电聚合物复合材料（CPCs）的机电性能和创造安全电磁环境提供了机制。在此，首先合成了TiCT MXene纳米片，然后利用其丰富的表面官能团，通过无氧化剂氧化聚合反应，以两种不同的MXene与单体比例将聚苯胺（PA）纳米纤维接枝到MXene表面。随后，深入研究了不同纳米材料负载量下聚偏氟乙烯（PVDF）基CPCs的电导率、电磁干扰屏蔽效能（SE）和力学性能。对于PVDF-MXene、PVDF-MXAN和PVDF-MXAN，在6.9 vol%负载量下分别获得了非常低的1.8 vol%渗流阈值和0.23、0.195和0.17 S/cm的优异电导率。与原始MXene复合材料相比，表面改性分别使PVDF-MXAN和PVDF-MXAN复合材料的电磁干扰屏蔽效能显著提高了19.6%和32.7%。改性纳米片显著提高的电磁干扰屏蔽效能归因于：（i）PA纳米纤维插入MXene层之间，导致更好的纳米片剥离；（ii）通过在纳米片和聚合物链之间构建类似电容器的结构，产生大量偶极和界面极化耗散；（iii）通过导电PA纳米纤维增强电磁干扰衰减。MXene纳米片的表面改性还增强了PVDF链与纳米片之间的界面相互作用，这使得PVDF基体的杨氏模量在PVDF-MXAN和PVDF-MXAN复合材料6.9 vol%负载量下分别提高了约67%和46%。
