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 substr ates is demonstrated. Depending on the reaction conditions, two differ ent morphologies are observed. At low temperatures (180 degrees C < T < 210 degrees C) and short reaction times, highly oriented and uniform thin films are formed, while at higher temperatures and/or longer rea ction times, small crystallites grow and orient on top of the POBA fil ms formed initially. Both morphologies correspond to phase II of POBA. The composite electron diffraction patterns of the PTFE/low temperatu re deposit clearly shaw 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%, corresp onding to the difference between the b(POBA) and a(PTFE) cell paramete rs. The POBA crystallites/POBA film mutual orientation with (001)(crys tallite)//(100)(film) and [010](crystallite)//[010](film), is analyzed in terms of POBA homoepitaxial interactions.