UV causes dramatic changes in aggregation with mixtures of photoactive and inert surfactants

Julian Eastoe; Margarita Sanchez Dominguez; Paul Wyatt; Andrew J Orr-Ewing; Richard K Heenan

doi:10.1021/la0496486

UV causes dramatic changes in aggregation with mixtures of photoactive and inert surfactants

Langmuir. 2004 Jul 20;20(15):6120-6. doi: 10.1021/la0496486.

Authors

Julian Eastoe¹, Margarita Sanchez Dominguez, Paul Wyatt, Andrew J Orr-Ewing, Richard K Heenan

Affiliation

¹ School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K. [email protected]

PMID: 15248693
DOI: 10.1021/la0496486

Abstract

Aqueous mixtures of photosensitive and inert surfactants have been prepared; photoreactions and changes in aggregation after irradiation have been characterized. The photosensitive component was a stilbene-containing gemini photosurfactant (E-SGP), and the inert surfactants were either DTAB (dodecyltrimethylammonium bromide) or one of two different gemini surfactants, 12-4-12 or 16-4-16 (butanediyl-1,4-bis(dodecyldimethylammonium bromide) or butanediyl-1,4-bis(hexadecyldimethylammonium bromide)). Small-angle neutron scattering (SANS) studies revealed that in general the initial nonirradiated mixed systems form vesicle-type aggregates (100-200 angstroms radius), in equilibrium with some smaller charged spheroidal or ellipsoidal micelles (approximately 20 angstroms radius). In all cases, UV irradiation resulted in disruption of these vesicles and the formation of charged micelles. 1H NMR showed that the main photoproduct is the cis, anti, cis dimer of E-SGP (ZEZ-DiSGP); hence, photochemically induced changes in the reactive SGP drive significant changes in the preferred aggregation structure. These results demonstrate the utility of photoactive surfactants in mixtures with inert analogues.