Poly (ethylene oxide)-block-poly (n-butyl acrylate)-blockpoly (acrylic acid) triblock terpolymers with highly asymmetric hydrophilic blocks: synthesis and aqueous solution properties

摘要

The synthesis and aggregation behaviour in aqueous media of novel amphiphilic poly(ethylene oxide)-block-poly(n-butyl acrylate)-block-poly(acrylic acid) (PEO–PnBA–PAA) triblock terpolymers werestudied. Terpolymers composed of two highly asymmetric hydrophilic PEO (113 monomer units) andPAA (10–17 units) blocks, and a longer soft hydrophobic PnBA block (163 or 223 units) weresynthesized by atom transfer radical polymerisation (ATRP) of n-butyl acrylate and tert-butyl acrylate(tBA), followed by selective hydrolysis of the PtBA blocks. These terpolymers are not directly soluble inwater but form defined spherical micelles by employing the dialysis method as confirmed by dynamiclight scattering (DLS) and cryogenic transmission microscopy (cryo-TEM). Based on terpolymerarchitecture and composition, a three-layered micellar structure comprising a PnBA core, a PEO/PAAmiddle layer, and a PEO outer layer is suggested. The micelles do not dissociate to very lowconcentrations and, therefore, are promising candidates for long-circulating drug delivery systems.Further, as evidenced by high-performance liquid chromatography (HPLC), the micelles can load andrelease, without burst effect, the hydrophobic drug paclitaxel.