Effect of salt and pH on surface active properties of comb rake-type polysiloxane surfactants

Comb rake-type polysiloxane surfactants, [PA-oligo(PO-b-EO) series and PA-oligo(PO-b-EO)Me series] were synthesized by the hydrosilylation reaction. To investigate the surface active properties of polysiloxane surfactants that have multiple hydrophobic and hydrophilic groups, the surface tension and sedimentation time of the aqueous surfactant solution were measured. Surface tension and cloud point (CP) tended to increase with an increase of the EO chain length and a decrease of the PO ratio. The surface tension of siloxane surfactants in the methoxy group was lower than that of the hydroxyl group. Surface tensions at pH 3 and 11 were higher than those in neutral pH values. When the inorganic electrolyte was added into the aqueous solution, the surface tension tended to decrease gradually due to the arrangement of surfactant molecules toward the interface of aqueous solution. The sedimentation time of the aqueous solution tended to decrease with an increase of the EO chain length, and a decrease of PO ratio. The sedimentation time according to the variation of pH values was similar to the results of surface tension.