Epitaxial Polymerization of Poly(p-oxybenzoate) on Friction-Transfer Poly(tetrafluoroethylene) Substrates

Epitaxial polymerization/crystallization of poly( p -oxybenzoate) (POBA) from p -acetoxybenzoic acid vapors on friction-transferred PTFE substrates is demonstrated. Depending on the reaction conditions, two different morphologies are observed. At low temperatures (180 °C < T < 210 °C) and short reaction times, highly oriented and uniform thin films are formed, while at higher temperatures and/or longer reaction times, small crystallites grow and orient on top of the POBA films formed initially. Both morphologies correspond to phase II of POBA. The composite electron diffraction patterns of the PTFE/low temperature deposit clearly show that the POBA thin films grow epitaxially, the (100) POBA plane contacting the (010) PTFE substrate surface. This epitaxy is achieved with a very good lattice mismatch of 0.4%, corresponding to the difference between the b POBA and a PTFE cell parameters. The POBA crystallites/POBA film mutual orientation with (001) crystallite //(100) film and [010] crystallite //[010] film, is analyzed in terms of POBA homoepitaxial interactions.