Effect of siloxane backbone length on butynediol-ethoxylate based polysiloxanes

A series of butynediol-ethoxylate based polysiloxanes (PSi-EOs) with same composition but different lengths of siloxane backbone were designed and synthesized via hydrosilylation reaction. Their physicochemical properties and application performances have been discussed. With the increase of the length of siloxane backbone, the critical aggregation concentration (CAC) decreases and the surface tension at CAC (γCAC) increases, but the dynamic adsorption at the air/water interface has no significant change. Above the CAC, all of these three surfactants can self-assemble into spherical aggregates of 100 to 500nm in aqueous solution. Moreover, the contact angle measurement on Paraffin film demonstrates that shorter siloxane backbone length of PSi-EO leads to lower contact angle and shows better spreading and wetting abilities. Using the foaming power test, PSi-EO with a longer siloxane backbone exhibits lower foaming and more effective anti-foaming properties in water.