Guiding Percolation by Bottlebrush Architecture: A Pathway toward Materials for Electronic Skin

Physical blending is a conventional strategy used to create desired property combinations in composite materials. However, blends of conductive composites are prone to high stiffness and brittleness. Furthermore, even at lower fractions, additives tend to undergo uncontrolled aggregation, which precludes percolation. We use coarse-grained molecular dynamics simulations to demonstrate the viability of the bottlebrush macromolecules as a template for dispersion and nanoconfined aggregation of poly(3-hexylthiophene-2,5-diyl) (P3HT). Our simulations prove that the densely grafted side chains promote segregation of dispersed P3HT molecules within the interbrush space, providing a kinetically favorable pathway for the formation of a percolated scaffold of functional moieties. The simulation results were corroborated by blending of linear-bottlebrush-linear PMMA-bbPDMS-PMMA copolymers with a controlled fraction of P3HT that can attain functional material with a percolation threshold above 10 wt% of P3HT and tissue-like mechanical properties. The formation of a percolated P3HT scaffold was confirmed by dynamic mechanical analysis, 2-point conductivity, and transmission electron microscopy.