Amphiphilic block copolymers of poly(N-vinyl pyrrolidone) and poly(isobornyl methacrylate). Synthesis, characterization and micellization behaviour in selective solvents

Abstract

Block copolymers of N-vinyl pyrrolidone (NVP) and isobornyl methacrylate (IBMA), PIBMA-b-PNVP, were prepared employing the RAFT polymerization technique. IBMA was polymerized first followed by the polymerization of NVP in the presence of a suitable fluoroalcohol to accelerate the crossover reaction. The copolymers were characterized by Size Exclusion Chromatography (SEC) and NMR spectroscopy. The thermal stability of these copolymers was studied via Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG), showing unique characteristics compared to the respective PIBMA and PNVP homopolymers. The micellization behavior was studied in THF, which is a selective solvent for the PIBMA blocks. The corresponding statistical copolymers, PNVP-stat-PIBMA were also examined to elucidate the effect of the macromolecular architecture on the micellar properties. Furthermore, the self-assembly behavior in aqueous solutions was studied for the PIBMA-b-PNVP block copolymers. Water is a selective solvent for the PNVP blocks. Static (SLS) and dynamic light scattering (DLS) were employed to study the micellar assemblies. The encapsulation of the hydrophobic compound curcumin within the micellar core of the micellar structures in aqueous solutions was investigated by UV–Vis spectroscopy and DLS measurements.