Alkyl Chain Positional Isomers of Dodecyl β-d-Glucoside:  Thermotropic and Lyotropic Phase Behavior and Detergency

A series of six dodecyl glucopyranoside surfactants, each with a single glucopyranoside headgroup attached sequentially along the chain from carbon 1 to carbon 6, have been prepared in order to systematically simulate “branching” in glucose-based surfactants. The thermotropic and lyotropic liquid crystalline properties of the series have been investigated, as well as the hard soil detergency of these surfactants. The introduction of “branching” into the alkyl chain strongly affects the packing of the molecules into crystals and liquid crystalline structures, thereby influencing the thermotropic properties and the surfactant/water binary phase diagrams. Attachment of the headgroup at the terminal carbon or at carbon 2 does not appreciably influence the surfactant behavior, while attachment at carbon 3, 4, 5, or 6 results in very different behavior from that of either 1 or 2. This discontinuous change is reflected in the detergency behavior of the surfactants and can be attributed to the change in length and shape of the surfactant molecules and the subsequent changes in intermolecular interaction.