Study on the effect of structure of polydimethylsiloxane grafted with polyethyleneoxide on surface activities

Twelve kinds of polydimethylsiloxane grafted with polyethyleneoxide (PDMS-g-PEO) were synthesized by two-step reactions: the preparation of silicone backbone containing methyl-hydrogen siloxane units and the following hydrosilylation reactions with PEO containing allyl groups. When the effects of structure of PDMS-g-PEO on the surface properties were investigated by comparing the each effect caused by EO content, EO chain length or the size of hydrophobe, the size of hydrophobe was found to be a critical factor for deciding surface tension rather than the content of EO. Significant decrease in the contact angle of the aqueous solution was observed when EO content of PDMS-g-PEO or the surfactant concentration increased. On the other hand, the viscosity of the surfactant solution at constant concentration slightly increased as EO content increased, but the difference was not significant. Dynamic surface tension measurement showed a decrease in the surface tension of the aqueous surfactant solution with an increase in the surfactant concentration. In addition, much longer times were required to reach an equilibrium compared with conventional nonionic or ionic surfactants due to the lower mobility of PDMS-g-PEO with high molecular weight.