Synthesis and characterization of novel perfluorinated polyimides with 3D-controlled structures for photonic applications

New Fluorine-Containing Diamine Monomers for Potentially Improved Polyimides

Two new fluorine-containing diamine monomers were designed with the goal of reducing charge transfer complex (CTC) interactions between neighboring chains in polyimides (i.e., high transparency/low color) while hopefully maintaining the well-known thermal stability and flexibility generally associated with polyimides. The proposed diamines have been prepared through (1) the functionalization of 1,3-bis[(pentafluorobenzyl)oxy]benzene with 4-aminophenol and (2) the addition of 2-chloro-5-nitrobenzotrifluoride to 4,4'-bicyclohexanol followed by reduction of the resulting dinitro compound. The new compounds have been characterized by multinuclear NMR and IR spectroscopy and high-resolution liquid chromatography-mass spectrometry as well as single-crystal X-ray diffraction on the new diamine prepared from 4,4'-bicyclohexanol. Not only was the structure of the proposed new diamine confirmed, but another interesting example of hydrogen bonding between an N-H proton and the π-system of an aromatic ring was observed and documented. Initial polymerizations have been carried out via the two-step imidization process.

Synthesis and evaluation of properties of novel aromatic poly(ether-imide) with benzazole pendent groups and flexible ether linkages

Three types of new bis(ether-amine) monomers such as 5-(2-benzimidazole)-1,3-bis(4-aminophenoxy)benzene (3), 5-(2-benzoxazole)-1,3-bis(4-aminophenoxy)benzene (4), and 5-(2-benzothiazole)-1,3-bis(4-aminophenoxy)benzene (5) were prepared in three steps, starting from the reaction of 3,5-dihydroxybenzioc acid with 4-fluronitrobenzene in N, N-dimethylformamide (DMF) solution in the presence of potassium carbonate, followed by catalytic reduction of the intermediate dinitro-carboxylic acids, and subsequent condensation of the resulting diamino-carboxylic acids and 1,2-phenylenediamine, 2-aminophenol or 2-aminothiophenol in polyphosphoric acid (PPA), respectively. Three series of modified poly(ether-imide)s (PEIs) bearing pendent benzimidazole, benzoxazole or benzothiazole groups were prepared from the bis(ether-amine)s with dianhydrides by a conventional two-stage process that included ring-opening polycondensation forming the poly(amic acid)s (PAA) and further thermal or chemical imidization forming poly(ether-imide)s. For comparative purposes, reference poly(ether-imide)s were also prepared by reacting bis(ether-amine) lacking pendent groups namely 1,3-bis(4-aminophenoxy)benzene (6) with the same dianhydrides under similar conditions. The modified polymers were obtained in quantitative yields with inherent viscosities between 0.52 and 0.83 dL g−1. Experimental results indicated that all the PEIs had glass transition temperature between 221 and 283 °C, the decomposition temperature at 10% weight loss between 480 and 572 °C under nitrogen.