Flexible nanoscale co‐continuous structures prepared by controlled crazing of ethylene‐octene elastomers and in‐situ polymerization of conductive networks

Abstract

AbstractAn approach based on controlled crazing and post‐polymerization was used to incorporate a nanoscaled conductive co‐continuous network into commercial ENGAGE™ Polyolefin Elastomers (POEs). Three POE films of differing crystallinity and phase morphology were stretched in a reactive mixture of acrylic polymerization precursors that possessed an affinity for the olefinic materials and acted as a surface‐active agent for craze promotion. As a result, a rigid acrylic hydrogel phase was grown in the void space associated with crazing, which prevented the formed channels from collapsing after mechanical stresses were removed. The hydrogel phase offered ion conductivity properties to the POE. Simply replacing the acrylic monomer with an aniline emulsion for polymerization did not lead to the same outcome in terms of a continuous network; the materials became insulative after the removal of mechanical stresses due to fragmentation of the polyaniline channels from the unrestrained elastic relaxation of the POE. This problem was overcome by solution‐casting POE with polycaprolactone (PCL) into films and, subsequently, partially dissolving and leaching PCL from the blend while a sample was stretched in an aniline emulsion medium containing formic acid. The residual PCL left in the crazes reinforced the polyaniline to prevent fragmentation, allowing the formation of a highly electron‐conductive secondary phase.