Poly(acrylic acid)-graft-poly(N-vinylcaprolactam): a novel pH and thermo dual-stimuli responsive system

Stimuli-responsive polymers have undoubtedly been of great interest in the past few decades due to a variety of potential applications in biomedical territory. Herein, we report a novel dual-stimuli responsive double hydrophilic graft copolymer system, poly(acrylic acid)-g-poly(N-vinylcaprolactam) (PAA-g-PNVCL), which could respond to changes in pH and temperature simultaneously. In our design, poly(acrylic acid) (PAA) was selected as a pH-sensitive moiety, whereas poly(N-vinylcaprolactam) (PNVCL) could be regarded as a thermo-sensitive one. The responsiveness of PAA-g-PNVCL to pH and temperature by itself was demonstrated in detail primarily: dynamic light scattering (DLS), fluorescence spectroscopy, and transmission electron microscopy (TEM) were employed to examine its pH-induced micellization behavior; H-1 NMR, DLS, and TEM were employed to examine its thermo-induced micellization behavior. Finally, its responsiveness to the combination of both stimuli was studied by UV-vis test.