Facile fabrication of pH-sensitive core–shell nanoparticles based on HEC and PMAA via template polymerization

Driven by the specific hydrogen bonding interactions, PMAA chains synthesized in situ during the template polymerization self-assemble with HEC template macromolecules, resulting in well-defined nanoparticles with cores of PMAA/HEC inter-polymer complexes and shells of HEC. Taking advantage of the specific hydrogen bonding interactions between the components, core–shell nanoparticles based on poly(methacrylic acid) (PMAA) and hydroxyethyl cellulose (HEC) can be efficiently prepared via facile one-step polymerization of MAA on HEC template in water. Various techniques were used to characterize in detail the sizes, morphology, and structures of the nanoparticles, as well as the interactions between the components. The core–shell structures of the nanoparticles were confirmed by TEM observation. Dynamic light scattering and fluorescence spectrometry were used to monitor the polymerization process, which indicates a size decrease and a hydrophobicity increase of the nanoparticles. A mechanism was proposed to explain the formation of core–shell nanoparticles during the template polymerization. The obtained nanoparticles are stable against urea, salt, temperature and in the storage; meanwhile, they exhibit pH-response: the volume of the nanoparticles increased more than six times as pH value of the medium increased from 2.8 to 3.7.