Key Laboratory of Applied Chemistry of Chongqing Municipality, School of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, China.
Nanoscale. 2017 Aug 10;9(31):11017-11026. doi: 10.1039/c7nr02322g.
Formation of highly conductive networks is essential for achieving flexible conductive polymer composites (CPCs) with high force sensitivity and high electrical conductivity. In this study, self-segregated structures were constructed in polydimethylsiloxane/multi-wall carbon nanotube (PDMS/MWCNT) nanocomposites, which then exhibited high piezoresistive sensitivity and low percolation threshold without sacrificing their mechanical properties. First, PDMS was cured and pulverized into 40-60 mesh-sized particles (with the size range of 250-425 μm) as an optimum self-segregated phase to improve the subsequent electrical conductivity. Then, the uncured PDMS/MWCNT base together with the curing agent was mixed with the abovementioned PDMS particles, serving as the segregated phase. Finally, the mixture was cured again to form the PDMS/MWCNT nanocomposites with self-segregated structures. The morphological evaluation indicated that MWCNTs were located in the second cured three-dimensional (3D) continuous PDMS phase, resulting in an ultralow percolation threshold of 0.003 vol% MWCNTs. The nanocomposites with self-segregated structures with 0.2 vol% MWCNTs achieved a high electrical conductivity of 0.003 S m, whereas only 4.87 × 10 S m was achieved for the conventional samples with 0.2 vol% MWCNTs. The gauge factor GF of the self-segregated samples was 7.4-fold that of the conventional samples at 30% compression strain. Furthermore, the self-segregated samples also showed higher compression modulus and strength as compared to the conventional samples. These enhanced properties were attributed to the construction of 3D self-segregated structures, concentrated distribution of MWCNTs, and strong interfacial interaction between the segregated phase and the continuous phase with chemical bonds formed during the second curing process. These self-segregated structures provide a new insight into the fabrication of elastomers with high electrical conductivity and piezoresistive sensitivity for flexible force-sensitive materials.
构建高度导电网络对于获得具有高力敏性和高导电性的柔性导电聚合物复合材料（CPCs）至关重要。在这项研究中，在聚二甲基硅氧烷/多壁碳纳米管（PDMS/MWCNT）纳米复合材料中构建了自分离结构，从而在不牺牲其机械性能的情况下表现出高压阻灵敏度和低渗流阈值。首先，将 PDMS 固化并粉碎成 40-60 目大小的颗粒（尺寸范围为 250-425μm），作为优化的自分离相以提高后续的导电性。然后，将未固化的 PDMS/MWCNT 基底与固化剂一起与上述 PDMS 颗粒混合，作为分离相。最后，再次固化混合物以形成具有自分离结构的 PDMS/MWCNT 纳米复合材料。形态评估表明，MWCNTs 位于第二固化的三维（3D）连续 PDMS 相中，导致超低渗流阈值为 0.003 体积% MWCNTs。具有自分离结构的纳米复合材料在 0.2 体积% MWCNTs 时具有 0.003 S m 的高电导率，而在常规样品中仅在 0.2 体积% MWCNTs 时获得 4.87×10 S m 的电导率。在 30%压缩应变下，自分离样品的应变系数 GF 是常规样品的 7.4 倍。此外，与常规样品相比，自分离样品还表现出更高的压缩模量和强度。这些增强的性能归因于 3D 自分离结构的构建、MWCNTs 的集中分布以及在第二固化过程中形成化学键的分离相与连续相之间的强界面相互作用。这些自分离结构为制造具有高导电性和压阻灵敏度的弹性体提供了新的思路，可用于柔性力敏材料。
