PCL(4k)-PEG(1k)-Thiol enables self-assembly to form micelles with the arrangment of polycaprolactone (PCL) core and PEG shell. The core regions can serve as hydrophobic drugs reservoir while the shell can provide protection against degradation. Moreover, the PEG shell also allows the "stealth behavior" which is a prerequisite for successful in vivo translation of nanomedicine to achieve long blood circulation and targeted delivery. The ester bonds of the polymer can be degraded via hydrolysis. The thiol moiety is reactive with maleimide or SPDP. Reagent grade, for research purpose.