Thermal-Sensitive PBMA-b-PNIPAAm Amphiphilic Block Copolymers Brushes and Their Assembling Micelles

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 of these polymer brushes was characterized and determined by nuclear magnetic resonance (H-1 NMR), and Fourier transform infrared spectrometry (Fr-IA). The micellar formation by these polymer brushes in aqueous solutions were detected by a surface tension technique, and the critical micelle concentration (CMC) ranged from 1.53 to 8.06 mg L-1. The morphology and geometry of polymer micelles were investigated by transmission electron microscope (TEM) and dynamic light scattering (DLS). The polymer micelles assume the regularly-spherical core shell structure with well-dispersed individual nanoparticles, and the particle size was in the range from 36 to 93 nm. The PNIPAAm segments exhibited a thermoreversible phase transition, so the resulting block polymer brushes were temperature-sensitive and the low critical solution temperature (LOST) was determined by UV-vis spectrometer at about 28.82-29.40 degrees C. The characteristic parameters of the polymer micelles such as CMC, micellar size and LOST values were affected by their compositional ratios and the length of hydrophilic or hydrophobic chains. The self-assembled micelles are expected to be used in specific biomedical fields as a candidate of drug controlled release carrier.