PCL(4k)-PEG(4k)-PCL(4k) is a biocompatible amphiphilic triblock polymer composed of a central hydrophilic PEG block and two terminal hydrophobic polycaprolactone (PCL) blocks. This self-assembling polymer can be used in controlled release formulation and nanoparticle formation for drug delivery applications. Terminal hydroxyl (OH) groups allows for further derivatization. Reagent grade, for research purpose.