Synthesis, micellization and caffeine drug release kinetics of novel PBMA-b-PNIPAAm block polymer brushes

Abstract

Brush-like block copolymers with poly(t-butyl methacrylate) (PBMA) and poly(N-ispropylacrylamide) (PNIPAAm) as side arms, PBMA-b-PNIPAAm, were designed and synthesized via a simple free radical polymerization route. The chemical structure and molecular weight of these polymer brushes were characterized and determined by nuclear magnetic resonance (1H NMR), Fourier transform infrared spectrometry (FT-IR) and gel permeation chromatography (GPC). The polymer brushes can spontaneously assembled into regularly spherical core–shell nanostructured micelles with well-dispersed individual nanoparticles in aqueous solutions, and physiochemical properties of the micelles formed were detected by a surface tension technique, nanoparticle analyzer, transmission electron microscope (TEM), dynamic light scattering (DLS) and UV–vis transmittance measurements. Low critical micelle concentration (CMC) and high zeta potentials revealed the micellar stability and the micellar particle size was in the range from 36 to 93nm by TEM and less than 200nm by DLS. The resulting block polymer brushes were temperature-sensitive with low critical solution temperature (LCST) about 28.80–29.40°C. These characteristic parameters were affected by their compositional ratios and the length of hydrophilic or hydrophobic chains. The evaluation for caffeine drug release and release kinetics demonstrated that the drug release and bioavailability may be mediated or improved by the temperature-induced structural changes of the micelles and different diffusion mechanism.