The synthesis and properties of siloxane-urethane copolymers aqueous nanodispersion using hydroxyalkyl and hydrohxypolyester terminated polydimethylsiloxane

Abstract

We synthesize siloxane-urethane copolymer aqueous dispersions by using hydroxypropyl terminated polydimethysiloxane (HAS) and hydrohxypolyester terminated polydimethylsiloxane (PES) as siloxane monomers and dimethylol propionic acid (DMPA) as intrachain emulsifier. The stable dispersions have the average sizes from 24 to 59 nm dependent on the reaction conditions. From the dispersions, the transparent films with the improved hydrophobicity are prepared. The water contacting angels of these films are enhanced by increasing the siloxane contents. In order to reveal the influences of the different chemical structures of siloxane, these films are also investigated about the UV-vis spectrum, tensile property, topography, and glass transition. It is obtained that the use of PES can obtain the films with better light transmission, around 95%. It is observed by atom force microscope that the as-synthesized siloxane-urethane copolymer films display less phase separation, agreeing well with the high transparency. Moreover, the rheological tests and model calculations are carried out to illustrate the effects of DMPA concentrations on the viscosities and correlation to the dispersion particle sizes. The as-synthesized aqueous nanodispersions promise to be used for the transparent coatings of hydrophobicity.