Construction of conductive percolation network with high efficiency in composite film via a novel sparsely partial wrapping strategy

Carbon nanotubes (CNTs) is a great potential reinforcing additives or conductive fillers for polymer composites. It is well known that interfacial properties between CNTs and polymer matrix have a critical effect on the properties of composites. Here, we demonstrate a novel strategy for preparing high efficient percolation networks of CNTs in polymer composite by partially wrapping of MWCNTs with crystallization induced self-assembly of pyrene end-capped poly(p-dioxanone)-block-poly(ethylene glycol) (Py-PPDO-b-PEG). The wrapped surface can prevent the aggregation of CNTs, while the bare surface may still induce enough interconnection of CNTs, resulting in high efficient percolation network. The wrapping density, which could be easily engineered by control the crystallization temperature of PPDO block, is essential to the formation of percolation networks. The composite film prepared from Py-PPDO-b-PEG@MWCNTs and PCL exhibited much improved conductivity especially at very low nanotube concentration compared to those from neat MWCNTs without any wrapping. Especially using Py-PPDO-b-PEG@MWCNTs prepared at 40 °C as the precursors, the composite film exhibits both best electrical conductivity (3-11 orders of magnitude higher than that of PCL/MWCNTs composites films at same MWCNTs contents) and mechanical properties, which could be attributed to the optimized wrapping density of this sample. Dense or excessively sparse wrapping may impede the interconnection and dispersity of the MWCNTs, respectively, and therefore resulted in decreased conductivities.