Unconventional Transitions of Poly(N-isopropylacrylamide) upon Heating in the Presence of Multiple Noncovalent Interactions

The reversible coil-to-globule transition of poly(N-isopropylacrylamide) in aqueous solution is a tenet of the physics of polymers. However, most of the studies have been limited on the transition induced only by the variation of hydrogen bonds. How and what the coil structure will develop into are unclear in the presence of other noncovalent bindings besides hydrogen bonds. Here we introduce noncovalent bindings of anion dipole into poly(N-isopropylacrylamide) aqueous system besides hydrogen bonds and hydrophobic interactions and first have observed that the variant temperature responses of hydrogen bonds and anion dipole bindings could make the coil structure of poly(N-isopropylacrylamide) unconventionally restructure into micelles, nanorods, vesicles, etc., but not only globule-like structure.