Synthesis and characterization of brush copolymers based on methoxy polyethylene glycol and poly(ε-caprolactone)

Brush copolymers composed of methoxy poly(ethylene glycol) (MPEG) and poly(ε-caprolactone) (PCL) have been synthesized by the ring-opening polymerization of ε-caprolactone initiated by hydroxyl function of thermally esterified MPEG-citrate in presence of stannous octoate. Citric acid (CA) acts as spacer between brush-like MPEG and the long chain of PCL. Existence of hydrophobic domains as cores of the micelles were characterized by ¹H NMR spectroscopy and further confirmed with fluorescence technique using pyrene as a probe. Critical micelle concentration (CMC) of the synthesized copolymer decreased from 0.019 to 0.0031 mg/mL on increasing the fraction of PCL. Along with the physicochemical study, the brush copolymers were explored for the preparation of nanoparticles by nanoprecipitation technique. The morphology and geometry of micelles were investigated by using DLS, AFM, and TEM. Hydrodyanamic dimensions of micelles were around 118 and 178 nm with the core size of 8-10 nm, which further aggregated to form secondary micelle of 60-90 nm. Such assembled polymeric micelles with its flexible dendritic MPEG corona could hold a promise for the immobilization (encapsulation) of hydrophobic drugs and subsequently promote sustained release so that it can be a good vehicle for anti-cancer drug deliverance.