As such, the entropy loss is more significant for the bulkier zwitterionic head-group than for PIBSI. When water is used as a solvent, the entropy gain by releasing adsorbed water molecules into the bulk can compensate for the loss of entropy in the surfactant molecule to give an overall favourable increase in entropy upon adsorption. In Figure , there is no such compensation from the iso-octane solvent since the entropy gain by releasing the solvent molecules into the bulk is less than the entropy loss of the surfactant during adsorption.