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 6O (refs 2, 3) molecule, 1b (Fig. 1). Polymer 1a, despite its extended π-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 la to have less interruptions of the p -molecular orbital delocalization along the backbone as compared with the single-stranded polymer poly(phenv lene vinylene), which is presently the material of prime interest for the active elements in light-emitting diodes 5,6 .