Preparation and characterization of narrowly distributed nanogels with temperature-responsive core and pH-responsive shell

Narrowly distributed spherical core-shell nanogels were prepared by a two-step aqueous dispersion polymerization. Core particles composed of cross-linked temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) were synthesized via aqueous dispersion polymerization and then used as nuclei for subsequent shell addition of pH-responsive poly(4-vinylpyridine) (P4VP). The morphology and structure of the core-shell particles were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the size distribution was determined by dynamic laser light scattering (DLLS). Temperature- and pH-induced volume phase transitions of the latex particles were also investigated by DLLS. The results show that the P4VP shell does not significantly perturb the temperature-induced volume phase transition of the parent core whether P4VP is ionized or not, and the deswelling behavior differs significantly from that of other polyelectrolyte gels within which the ionic groups are randomly distributed.