Preparation of pH-sensitive nanoparticles of poly (methacrylic acid) (PMAA)/poly (vinyl pyrrolidone) (PVP) by ATRP-template miniemulsion polymerization in the aqueous solution

Employing polymethacrylic acid (PMAA) as the template and N -vinyl pyrrolidone (N-VP) as monomer, the ATRP-template miniemulsion polymerization was carried out in the aqueous medium by using MBP/CuBr/bpy as initiator. The results were characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), and gel permeation chromatography (GPC). It was observed that the stable particles exhibited amphoteric pH sensitivity, namely that in the range of pH 3.0 to 5.0, the particles precipitated, whereas beyond the range the particles were stable and swollen as pH varied. Moreover, the pH range was variable according to the molecular weight of PVP. The results of GPC indicated that the molecular weight of template polymer PMAA was duplicated by the daughter polymer PVP. Being noncross-linked, unlike the common microgels, the hydrodynamic diameter dramatically increased in a very narrow pH range, e.g., pH 5.5 –6 and 2.0–2.5. Finally, the nanoparticles of PMAA/PVP were applied for the controlled release of rifampicin (RFP) and doxorubicin (DOX).