Highly stretchable conductive MWCNT–PDMS composite with self-enhanced conductivity

Abstract

Soft and highly stretchable, yet conductive elastomers are essential in development of next generation electronic devices. However, electrical conductivity and mechanical stretchability are normally mutually exclusive properties since good conductors are rigid, and stretchable materials are inherently soft. Furthermore, maintained conductivity at high elongation is difficult to achieve because of the particle break-up due to the imposed large mechanical stresses on the percolated conductive fillers in contrast to much lower stresses on the soft and compliant elastomer matrix. Herein, a novel, simple, and effective preparation method is presented for fabricating highly stretchable conductive elastomers, consisting of multi-walled carbon nanotubes (MWCNTs) as a conductor and poly(dimethylsiloxane) (PDMS) as a soft matrix. As a result of the preparation method, stretch-enhanced conductivity is observed due to the prepared “hairy” particles effectively constructing further conductive pathways upon elongation. The “hairy” structures result from entrapped MWCNTs uniformly dispersed into low-molecular weight silicone polymers that are lightly crosslinked before being introduced into a silicone network resulting from silicone polymers of longer length to create a so-called heterogeneous bimodal network. Through the advanced, yet simple, mixing procedure followed by curing of the silicone matrix, it is possible to prepare conductive MWCNT/PDMS elastomers that can be elongated up to 200%. The prepared system shows high initial conductivity of 0.038 S m⁻¹ with 2.6 phr (parts per hundred rubber) MWCNTs and constant conductivity throughout the 160% deformation range. The prepared MWCNTs/PDMS composite composes a new class of stretchable conductive materials with potential applications in next generation electronics.