We have designed, synthesized, and purified a novel three-armed star polymer consisting fan elastin-like polypeptide (ELP) followed by a negatively charged trimer-forming oligomerization domain at the C-terminus. In low salt conditions, the water-soluble trimers assemble into micellar particles as small as 25 nm in diameter when heated to temperatures above their transition temperature. The size of these micelles can be controlled by adjusting salt and cosurfactant concentrations. They are stable at elevated temperatures but will dissociate into the individual trimers when the temperature is again decreased below the transition temperature. Their behavior at high temperatures is quite different than typical ELP constructs, which initially form large aggregates followed by phase separation into a coacervate and soluble fraction. The polypeptide consists of 40 pentapeptide repeats of glycine valine glyeine-valine-glycine-valine-proline (GVGVP) followed by the 27 amino acid foldon domain. It is expressed in E. coli and purified by thermal transition cycling.