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Microphase-Separated PE/PEO Thin Films Prepared by Plasma-Assisted Vapor Phase Deposition

Abstract: 
Immiscible polymer blends tend to undergo phase separation with the formation of nanoscale architecture which can be used in a variety of applications. Different wet chemistry techniques already exist to fix the resultant polymeric structure in predictable manner. In this work, an all-dry and plasma-based strategy is proposed to fabricate thin films of microphase-separated polyolefin/polyether blends. This is achieved by directing (−CH2−)100 and (−CH2−CH2−O−)25 oligomer fluxes produced by vacuum thermaldecomposition of poly(ethylene) and poly(ethylene oxide) onto silicon substrates through the zone of the glow discharge. The strategy enables mixing of hermodynamically incompatible macromolecules at the molecular level, whereas electron-impact-initiated radicals serve as cross-linkers to arrest the subsequent phase separation at the nanoscale. The mechanism of the phase separation as well as the morphology of the films is found to depend on the ratio between the oligomeric fluxes. For polyolefin-rich mixtures, polyether molecules self-organize by nucleation and growth into spherical domains with average height of 22 nm and average diameter of 170 nm. For equinumerous fluxes and for mixtures with the prevalence of polyethers, spinodal decomposition is detected that results in the formation of bicontinuous structures with the characteristic domain size and spacing ranging between 5 × 101 −7 × 101 nm and 3 × 102−4 × 102 nm, respectively. The method is shown to produce films with tunable wettability and biologically nonfouling properties.