Layered Thin Film Deposition via Extreme Inter-Brush Slip in a Lamellar Block Copolymer

Creating ultrathin films via ballistic impact-induced frictional material transfer could be a new approach for additive manufacturing compared with current solvent-assisted polymer coatings. The covalently bonded A block brushes and B block brushes are robust mechanical units in A/B lamellar diblock copolymers (BCPs). The parallel brush-brush interfaces with low entanglement density present a unique set of slip planes that can undergo extreme deformation by shearing and delamination by tensile forces. Impact of microspheres comprised of concentric glassy-rubbery brush layers against a rigid substrate at ballistic strain rates causes adiabatic shock heating that permits compressional thinning of the bottommost layers via slip over both types of BCP brushes. In cooler regions, the mechanical contrast between the glassy A blocks and rubbery B blocks induces extensive slip across the rubbery block brushes. For angled impacts, the increased shear stress enhances brush slip and the particle slides across the substrate accompanied by delamination across the slip planes and unique frictional transfer of discrete B-block-A A-block B layers.