Formation of high loading flexible carbon nanofiber network composites

Functional nanofiber network composites (FNNCs), which consist of high loading of carbon nanofiber (CNF) within a flexible silanol terminated poly(dimethylsiloxane) (PDMS) matrix, were produced and characterized. Loadings up to 50 wt.% CNF were used to ensure the formation of a nanofiber network that combined the high conductivity of the CNF with the flexibility of the PDMS matrix. The CNF were functionalized with PDMS groups (CNF–PDMS) which were designed to (i) enhance compatibility between the matrix polymer and the CNF to improve processability and surface wetting and/or (ii) participate in polymerization reaction with oligomeric silanol terminated PDMS. Mechanical testing showed that composites produced with CNF–PDMS at 30 wt.% loading exhibited 2–18-fold increases in modulus, tensile strength and toughness compared to composites produced with pristine CNF. The inclusion of CNF resulted in decreases in strain relative to base PDMS. While the electrical conductivity of the FNNC decreased when using functionalized relative to pristine CNF, in all cases the conductivity was sufficient for many applications of interest.