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

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.