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

Abstract

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.

Influence of Entanglements on Ultrahigh Strain Rate Deformation of Polystyrene Microprojectiles

“…The launch pad used for projectiles is similar to the previous LIPIT studies. 14 A 22 × 22 mm microscope cover glass (Fisher brand 12-541-B) was coated with 10 nm of gold using a sputter coater (Denton Desk V Sputter System). A two-part PDMS kit (Sylgard 184, Dow Chemical), consisting of a PDMS monomer and a PDMS hardener with weight ratio of 10:1 was mixed and then degassed in a vacuum oven (Lab-Line 3628-1 Squaroid Duo-Vac Vacuum Oven) at room temperature for 1 h; then, 20 μm of PDMS film was transferred onto gold-coated cover glass slides by a spin coater (WS-400BZ-6NPP/LITE) at 4000 rpm.…”

“…The launch pad used for projectiles is similar to the previous LIPIT studies . A 22 × 22 mm microscope cover glass (Fisher brand 12-541-B) was coated with 10 nm of gold using a sputter coater (Denton Desk V Sputter System).…”

“…The polymer microspheres suspended in water were drop cast onto the launch pad to dry before selection of individual particles for projectile impact. The perpendicular impact by LIPIT of the spheres onto the rigid substrate dominantly produces axisymmetric compression and shear followed by tension as the sphere flattens and deforms outward (Figure ).…”

“…The polymer microspheres suspended in water were drop cast onto the launch pad to dry before selection of individual particles for projectile impact. The perpendicular impact by LIPIT of the spheres onto the rigid substrate dominantly produces axisymmetric compression and shear followed by tension as the sphere flattens and deforms outward 14 (Figure 1). The evolution of the impact-induced shock wave, accompanied by the shock-induced stress state and thermal rise for the PS projectile were simulated using the Ansys LS-DYNA Multiphysics solver and are shown in Figure 1 for an impact velocity of 800 m/s (see Figures S2−S4 and the model description in Supporting Information).…”

Extreme Plasticity, Adhesion, and Nanostructural Changes of Diblock Copolymer Microparticles in Cold Spray Additive Manufacturing

“…The AW of PS84 is expected to have an upper limit higher than the velocity range tested in this study, and an enormous thermal effect from plastic work is anticipated at the upper limit of the AW resulting in a partial-rubbery domain near the collision interface. The continuous morphology of the PS glassy domain of PS87-PDMS40 was supposed to limit shear motions of the PDMS rubbery domain, 23 and the resultant plastic deformations of μPs were also limited. In other words, the interconnected rubbery domain of PS83-PDMS83 allowed further plastic deformation and promoted adhesion.…”