Physicochemical Properties of Monolayers of a Gemini Surfactant with a Minimal-Length Spacer
Srikant Kumar Singh, Alfred Yeboah, Wei Bu, Pan Sun, Matthew F. Paige
Abstract
Fundamental physical chemical properties of monolayers formed from a new anionic gemini surfactant with a minimal-length (single-bond) spacer unit have been investigated at the air–water interface and compared with those of monolayers formed from affiliated comparator surfactants. The minimal spacer surfactant, dubbed C18-0-C18, exhibited strikingly different packing characteristics from an anionic gemini surfactant with a comparatively bulkier headgroup, including the formation of close-packed, crystalline films, and shared similar characteristics to simple fatty acid-based monolayers. Monolayers of C18-0-C18 also exhibited good stability at the air–water interface and transferred with reasonable efficiency to solid substrates, although the film integrity was compromised during the transfer. Results from this work suggest that the single-bond spacer approach might be more broadly useful for designing gemini surfactants that pack efficiently into ordered monolayers.