Synthesis and Characterization of Fully Deuterated Upilex Type Polyimides

Polyimide films are materials of choice as membrane shutters of the hohlraum that contains a plastic microshell in which nuclear products are located to carry out Inertial Confinement Fusion experiments. In addition to high mechanical properties, polymer membranes must exhibit a high transparency in the infrared (IR) wavelengths range between 2.86 and 4 m (3500 and 2500 cm^-1) to allow the IR assisted deuterium-tritium ice layer redistribution. UpilexTM type polyimides exhibit the desired mechanical properties but are not transparent in this wavelengths range due to the aromatic C-H stretching bands. In order to provide the required optical properties, the hydrogen atoms must be substituted by deuterium atoms.In the present contribution, we wish to report the first synthesis of a fully deuterated UpilexTM type polyimide. Optimized ways of synthesis and purification for the two deuterated monomers 3,3ʹ,4,4ʹ-biphenyltetracarboxylic dianhydride (BPDA-d6) and p-phenylene diamine (PDA-d4) have been developed. These monomers have been used to prepare deuterated poly(amic-acid) solutions in NMP. Thermal treatment of films obtained from these solutions gives rise to deuterated Upilex type polyimide films. These films show a high transparency in the 2.86-4 m region. The synthesis and the characterization of this new deuterated polymer will be discussed.