Preparation of nanogels with temperature-responsive core and pH-responsive arms by photo-cross-linking

The preparation of temperature-responsive colloidal nanogels with a pH-responsive shell could be achieved by photo-cross-linking of poly(N-isopropylacrylamide) (PNIPAAm) graft terpolymers. The graft terpolymers were synthesized from NIPAAm, poly(2-vinylpyridine) (P2VP) macromonomers, and a chromophore monomer based on dimethylmaleimide (DMIAAm). The resulting solutions of nanogel with temperature-responsive core and chemically bounded (P2VP) arms exhibited more stablility upon heating and low pH as compared to the corresponding PNIPAAm nanogels. A large transition of the average hydrodynamic diameter of the gels could be observed by increasing either the temperature above 32 degreesC or the pH above 5. It was also demonstated that it is possible to obtain a response to one stimulus without interfering with the other stimulus. Dynamic light scattering (DLS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) were used for characterization of the core-shell nanogels.