Synthesis, Surface Activities, and Aggregation Behaviors of Butynediol-ethoxylate Modified Polysiloxanes

Five different butynediol-ethoxylate modified polysiloxanes (PSi-EO) were designed and synthesized via two-step reactions: the preparation of low-hydrogen containing silicone oil (LPMHS) by acid-catalyzed polymerization and the following hydrosilylation reaction with 1,4-bis(2-hydroxyethoxy)-2-butyne. The chemical composition of each product was confirmed by FT-IR, H-1 NMR, and Si-29 NMR. The surface activities and aggregation behaviors of PSi-EO surfactants in aqueous solution were studied systematically using surface tension, dynamic light scattering (DLS), transmission electron microscopy (TEM), and contact-angle methodologies. Relatively low critical aggregation concentration (15-34 mg.L-1) and surface tension (similar to 25 mN.m(-1)) were measured for PSi-EO aqueous solution. The rate of surface tension reduction increased both with increasing PSi-EO concentration and with increases in the proportion of hydrophilic moieties within the synthesized compounds. Furthermore, DLS and TEM studies revealed that PSi-EO self-assembled in aqueous solution to form spherical aggregates. Contact-angle measurements conducted upon low-energy paraffin film surfaces demonstrated that PSi-EO exhibited efficient spreading at concentrations above the critical aggregation concentration.