Synthesis, Structure, Chromatic Properties, and Induced Circular Dichromism of Polydiacetylenes with an Extended Conjugated System in the Side Chain

We synthesized PDAs with a 4‐carboxyphenyl substituent directly connected to the conjugating main chain in order to investigate the effects of the side chain structure on the chromatic properties of the polymers. A series of 1,3‐alkadiynyl‐4‐benzoic acids ( m,Ph ‐DA‐CO 2 H ) and their 1‐naphthylmethylammonium salts ( m,Ph ‐DA‐Naph ) were prepared and polymerized under UV and γ ‐ray irradiation. The resulting poly( m,Ph ‐DA‐CO 2 H )s had absorption bands in their UV‐vis spectra in a wavelength region longer than those for the poly( m,Ph ‐DA‐Naph )s and the other PDAs. We report the first example of the induced circular dichromism of poly( m,Ph ‐DA‐CO 2 H ) in the combination with a chiral (1‐cyclohexyl)ethylamine in the dispersion and in the solid state by an acid/base interaction.