Amphiphilic Multi-arm Star Copolymer: Synthesis, Characterization And Application

This paper was mainly studied on the synthesis, modification, self-assemble behavior of the amphiphilic multi-arm star copolymer polyethylenimine-block- poly(ε-carprolatone)(PEI-b-PCL) and their encapsulation and release property as the drug delivery.Catalyzed by the Tin(II) 2-ethylhexanoate (Sn(Oct)2), hyperbranched polyethylenime (PEI) have successfully iniatiated ring-opening polymerization of the ?-carprolatone, to obtain the amphiphilic multi-arm star copolymer with poly(?-carprolatone) as shell and polyethylenime (PEI) as core. Due to the polar difference of the PCL arms and the PEI inner core, the obtained star copolymer could act as the unimolecular micelle to encapsulate the water-soluble guests. Their guest encapsulation and release behavior could be adjusted by the modification of the PCL shells and PEI cores. Modifying the PCL arms by the esterification or quaternizing the PEI core not only could efficiently enhance the unimolecular micelle's encapsulation capability, but also slow down the realease rate of the encapsulated guest molecules in the vivo environment in a large extent. Moreover, the carbon number of the aliphatic acid used for esterification and the valences of anionic counter-ions in the quaternized polymers have some effect on their encapsulation capability.The multi-arm star copolymer PEI-b-PCL and their terminal esterified products by the Methacrylic acid(MAA) could all form the self-assemble micelle. By the polymerization of the carbon carbon doubt bond in the core of micelle iniated by the water-soluble iniatiator V50, the colvantly stable inner core was obtained, along with the numerous closely aligned PCL arms and the PEI outer shells which had partly cross-linked PCL arms in rule. This"flower-like"stable micelle has very strong encapsulation capability for the non-polar guests, comparing to the traditional structureal stable micelle. Furthermore, comparing to the original micelle PEI-b-PCL- MAA, this structure conversion have make them lost the encapsulation capability to the anionic guests, but enabled them to encapsulate the cationic guests.