Photochemical behavior of micellized 4-(4?-alkylstyryl)pyridinium salts

Abstract

New photochromic surfactants, 1‐alkyl‐4‐(4′‐alkylstyryl)lpyridinium halides (CnStzRX; n = 0, 4, 6, 8; R = Me, Et, CH2CH2OH, n‐Bu, n‐C9H19; X = Br, I), were synthesized and the photochemical behavior of their micellar aggregates in water was characterized in relation to non‐micellizing 1‐methyl‐4‐stilbazolium ions. Reversible trans‐cis isomerization through a photothermal cycle was observed for the micellized CnStzRX. Furthermore, photoreactions upon prolonged irradiation of CnStzRX micelles resulted in a 3–31% formation of thermodynamically least stable syn‐head‐to‐head and ca. 3% of anti‐ head‐to‐head dimers. These findings indicate that the self aggregation process of CnStzRX may provide some topologically organized microenvironment affecting the steric and like‐charge repulsions of the aggregate components.