SYNTHESIS OF A FULLY UNSATURATED ALL-CARBON LADDER POLYMER

FOR some time we have been trying to synthesize structurally perfect, fully unsaturated, double-stranded (ladder) polymers(1); such polymers might combine favourable electronic properties with processability. Here we report the successful synthesis of the fully unsaturated ladder polymer 1a (Fig. 1), by way of the Diels-Alder precursor polymer 7 (Fig. 4). The structure of 1a closely resembles the hypothetical open-chain, Polymeric analogue of the belt-region of the icosahedral C-60 (refs 2, 3) molecule, 1b (Fig. 1). Polymer 1a, despite its extended pi-conjugation, is stable in oxygen and may therefore be of interest for electroluminescence and photovoltaics applications(4). Owing to both the relatively mild reaction conditions required for its generation and its double-stranded structure, we expect 1a to have less interruptions of the pi-molecular orbital delocalization along the backbone as compared with the single-stranded polymer poly(phenylene vinylene), which is presently the material of prime interest for the active elements in light-emitting diodes(5,6).