Complementary multiple hydrogen bonds stabilize thermo-sensitive supramolecular structures prepared from poly(N-isopropyl acrylamide) and adenine-functionalized poly(ethylene oxide)

In this study, we synthesized a poly( N -isopropylacrylamide) (PNIPAm) through the polymerization of N -isopropylacrylamide in distilled water with azodiisobutyronitrile as the initiator and a bisadenine-functionalized poly(ethylene oxide) (A-PEO-A) from the reaction of adenine with a difunctionalized toluenesulfonyl-PEO. When blended together in distilled water, PNIPAm and A-PEO-A formed supramolecular aggregates stabilized through complementary multiple hydrogen bonds between the amide groups of PNIPAm and the adenine units of A-PEO-A. Fourier transform infrared spectroscopy, 1 H nuclear magnetic resonance spectroscopy, transmission electron microscopy, dynamic light scattering, and rheometry revealed the thermo-sensitive behavior and viscoelastic properties of the supramolecular assemblies.