Synthesis of pH-responsive cellulose-g-P4VP by atom transfer radical polymerization in ionic liquid, loading, and controlled release of aspirin

A pH-responsive cellulose-g-P4VP copolymer was synthesized by atom transfer radical polymerization (ATRP) in ionic liquid 1-allyl-3-methylimidazolium chloride [AMIM]Cl. The polymer structure was characterized by Fourier transform infrared (FT-IR), 1 H nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The P4VP brushes that were covalently bonded to the cellulose backbone had a narrow molecular weight distribution, which was helpful for use in drug loading. The loading and controlled release of drug using aspirin as model drug in the micelles obtained the cellulose-g-P4VP copolymer was investigated. The structure and size of the copolymeric micelles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and ultraviolet–visible (UV-Vis) spectroscopy, respectively. Blank micelles presented a stably spherical morphology with dimeter about 90 nm in aqueous solution. The resultant micelles had clear pH-sensitivity with a pH-dependent phase transition point at a pH of about 5.7. Drug-loaded micelles had a spherical, core–shell structure with dimeter about 150 nm. The polymeric micelles revealed an excellent controlled drug release at different pH values and the cumulative release of aspirin in phosphate buffer reached to 86.4% at pH 5.8, 60.9% at pH 7.4 and 42.2% at pH 8.0.at 50 h. The pH-sensitive cellulose-g-P4VP copolymer had an enormous potential as carriers for released drug delivery.