SOLUBLE, RIGID-ROD POLYIMIDES WITH DYE-CONTAINING SIDE-GROUPS VIA A NOVEL PRECURSOR ROUTE

Soluble, rigid-rod precursor polyimides were prepared via Pd-catalyzed copolycondensation of -N,N'-bis(4-bromo-2,5-didodecylphenyl)pyromelli tic diimide, -N,N'-bis(4-bromo-2,4-didodecylphenyl)pyromellitic diimid e, and 2,5-didodecylbenzene-1,4-diboronic acid. From these precursors, soluble, dye-containing polyimides were obtained by nucleophilic subs titution of the phenoxy side groups for (a) 4-hydroxyazobenzene, (b) 4 '-nitro-4-hydroxyazobenzene, (c) 4-[(4-nitrophenyl)azo]-1-naphthol ('' magneson II''), and (d) '-dimethyl-4-[(2-hydroxy-1-naphthyl)azo]azoben zene (''sudan red B''), respectively. An almost quantitative exchange was achieved in the case of the sterically less demanding dyes (a and b); a low conversion was observed for the bulky dyes (c and d). Throug hout, no evidence for chain degradation or other side reactions during the substitution reaction was found by analyzing the products by high -field NMR spectroscopy and membrane osmometry.