PCL(4k)-PEG(2k)-Thiol contains two distinct polymers, a hydrophobic polycaprolactone (PCL) block and a hydrophilic PEG block, with terminal thiol for reaction with maleimide. The polymer can form micelles in water with PCL core and PEG shell formation. The core can be used to entrap hydrophobic drugs for controlled release drug delivery. Reagent grade, for research purpose.