(556h) Polybenzoxazole Films Fabricated Using Vapor Deposition Polymerization

Polybenzoxazoles (PBO) are well known for their outstanding tensile properties, thermal stability, and solvent resistance. PBOs are traditionally prepared through condensation of terephthalic acid with a diamino-resorcinol compound in the presence of poly(phosphoric acid). We are developing solventless routes to simplify processing and to enable defect-free, micron-thick films of polybenzoxazoles. In this study, poly (amic acid) films were grown from the vapor phase by controlling the evaporation of two monomers: dihydroxybenzidine (DHB) and pyromellitic dianhydride (PMDA). High quality films were obtained only when the molar fluxes of each monomer were equal. Upon curing, thermal rearrangement of poly(amic acid) to polyimide, and subsequently to polybenzoxazoles, was confirmed using FT-IR spectroscopy. Mechanical properties of resulting films are comparable to their solution-cast analogs. We are currently exploring vapor deposition of PBOs with different (diamine / dianhydride) and (diamine / di-acid chloride) combinations to investigate how a structure's internal rotational degrees of freedom affect the resulting material's solid-state mobility. These materials have potential applications as gas separation membranes and as components in laser fusion targets.