LIQUID-LIQUID PHASE-SEPARATION AND ORIENTED GROWTH OF POLY(ARYL ETHER ETHER KETONE) ON FRICTION-TRANSFERRED POLY(TETRAFLUOROETHYLENE) SUBSTRATES

The morphology and orientation of poly(aryl ether ether ketone) (PEEK) crystallized in the presence of friction-tranferred PTFE layers have been studied by optical and electron microscopy, electron diffraction, and FTIR. Deposition and orientation of PEEK is successfully achieved by a two-stage procedure involving (i) liquid-liquid phase separation by slow absorption of water in a dilute methanesulfonic acid solution and (ii) aggregation-crystallization of the polymer-enriched droplets. PTFE substrates are shown to induce the crystallization of PEEK at a very early stage of the phase separation process. Electron diffraction and FTIR investigations demonstrate that the as-deposited PEEK films have a single crystal-like structure, with the chain axes of both polymers oriented parallel to each other and the PEEK zigzag plane oriented parallel to the (100) PTFE substrate surface. This well-defined polymer/polymer epitaxial relationship rests on a very good matching between (a) the chain axis periodicities and, (b) more importantly, the deposit and substrate interchain distances.