Spontaneous spreading of surfactant solutions on hydrophilic surfaces

The spontaneous spreading of surfactant solutions on hydrophilic surfaces i s investigated. The systems are solutions of nonionic CnEm surfactants in e thylene (EG) and diethylene glycol (DiEG). The parameters of the study are the ratio c* of the concentration of surfactant to the critical micellar co ncentration, and the relative humidity RH of the atmosphere. Above some RH threshold, the spreading is controlled by Marangoni effect and is accompani ed by dendritic contact line instabilities. The mobility of the pure surfac tant on the solid surface is the key parameter for the start of that flow, and for the structure of the instability pattern. (C) 1999 Elsevier Science B.V. All rights reserved.