Synthesis of star-shaped PCL-based copolymers via one-pot ATRP and their self-assembly behavior in aqueous solution

A series of star-shaped poly(E >-caprolactone) (PCL)-based diblock and triblock copolymers containing 2-(dimethylamino)ethyl methacrylate (DMAEMA or DMA) and oligo(ethylene glycol)monomethyl ether methacrylate (OEGMA or OEG) were synthesized by one-pot atom transfer radical polymerization (ATRP) using a sixarm PCL-based macroinitiator. The precursor and the resultant copolymers were analyzed via proton nuclear magnetic resonance spectra (H-1 NMR) and size exclusion chromatography (SEC). The monomer reactivity ratios for DMAEMA (r (1)) and OEGMA (r (2)) were estimated to be near unity and r (1)xr (2)=1, which indicates the random distribution of the monomers in the final copolymers. Self-assembly behavior of these copolymers was investigated by fluorimetry, H-1 NMR, dynamic light scattering (DLS), transmission electronic microscopy (TEM), potentiometric titrations, and zeta potential measurements. The results suggested that the star copolymers were responsive to salinity depending on their composition and structure.