PCL(1k)-PEG(3k)-Thiol comprises two distinct hydrophobicity blocks, i.e. polycaprolactone as a hydrophobic block and PEG as a hydrophilic block. It has terminal thiol for reaction with maleimide. The polymer can self-assemble in aqueous media and be used as strategies for sustained drug delivery using micellar nanocarriers. Reagent grade, for research purpose.