PCL(2k)-PEG(3k)-SPDP comprises two distinct block of polymers, i.e. hydrophobic polycaprolactone (PCL) and hydrophilic PEG blocks. The SPDP is reactive with thiol to form a disulfide linkage via thiol exchange reaction. Upon dispersion in water, the polymer self-assembles with the PCL being shielded from water by the PEG. The PCL core can be used to encapsulate hydrophobic drugs. Reagent grade, for research purpose.