PCL(2k)-PEG(2k)-PCL(2k) is a triblock ABA amphiphilic polymer. In water, the hydrophilic PEG block is shielding the hydrophobic polycaprolactone (PCL) blocks from the water. Therefore, hdyrophobic drugs can be encapsulated in the core of the nanoparticles. The polymer can be hydrolyzed on their ester bonds. The hydroxyl (OH) terminals can be further derivatized easily. Reagent grade, for research purpose.