Photoinitiated degradation of poly(diacetylene)s in solution by random chain scission

Poly(diacetylene)s dissolved in common organic solvents undergo random chain scission, if irradiated by UV‐light. The pure polymers and their solutions are, however, stable, if they are photoirradiated within the main‐absorption band of the polymer backbone. The usual triplet sensitizers, especially in the presence of oxygen, and radical donors such as 2,2′‐azoisobutyronitrile (AIBN) enhance the rate of photodegradation. Suitable dyes are able to sensitize the chain‐scission in the visible regions as well. Random chain scission occurs also in the dark, but only at temperatures above room temperature and is enhanced by the addition of radical‐donors, e.g. AIBN. A mechanism of chain scission, induced by the attack of a radical to a multiple bond of the polyconjugated backbone of the polymer is proposed.