Emulsions Stabilized with poly(Hydroxyethyl Acrylate-co-Coumaryl Acrylate-co-2-Ethylhexyl acrylate)

Thermo- and photo-responsive emulsions were prepared using mineral oil as an oil phase and a thermo- and-photo-sensitive polymer as an emulsifier. Hydroxyethyl acrylate (HEA) was copolymerized with Coumaryl acrylate (CA) and 2-Ethylhexyl acrylate (EHA) by a free radical reaction with the content of CA in the reaction mixture being varied (0, 0.5, 1, 2, 3mol%) and the content of EHA being kept constant (2mol%). CA was used as a photo-responsive comonomer and EHA was used as a hydrophobic comonomer to endow the copolymer with amphiphilicity. The copolymers prepared using the HEA/CA/EHA mixture where CA content was 1, 2, 3mol% exhibited a phase transition in the range of 20 degrees C- 45 degrees C, and the phase transition temperature decreased with increasing the content. The CA of the copolymers was readily dimerized under the irradiation of UV (365nm. 400 W) and the dimerization degree was 27%-47% in 60min. The droplet size of emulsions significantly increased with increasing the temperature from 27 degrees C- 50 degrees C, possibly due to the thermal contraction of the copolymers. Also, the size markedly increased by 60min-irradiation of the UV light, possibly because of the photo collapse of the copolymers.