High-Heteronucleobase-Content Polystyrene Copolymers Prepared Using Click Chemistry Form Supramolecular Structures With Melamine Through Complementary Multiple Hydrogen-Bonding Interactions

Supermolecules of poly(N-isopropylacrylamide) complexating Herring sperm DNA with bio-multiple hydrogen bonding

In this study we used the poly(N-isopropylacrylamide) (PNIPAAm) as a medium to blend with an organic DNA, herring sperm DNA (HSD), to generate PNIPAAm-HSD supramolecular complexes. Bio-multiple hydrogen bonding (BMHB) between PNIPAAm and HSD was investigated that changed the temperature responsiveness of PNIPAAm relatively to the HSD concentrations. With blending the HSD into PNIPAAm matrix, the phase separation in solution is completely opposite from that of neat PNIPAAm. Surface property in static water contact angle (SWCA) is also opposite from that of pure PNIPAAm upon increasing HSD content over 60%. In addition, we found that the PNIPAAm and HSD self-assembled a specific triangle-like structure at a PNIPAAm-to-HSD weight ratio of 1:4 at 25°C; while the triangle-like structure disappeared with increasing temperature to 45°C. Furthermore, both PNIPAAm and HSD could be regarded as insulator, but it transformed into a semiconductive matter after blending with the HSD. Incorporation of organic DNA with hydrogel could significantly change their properties, which might facilitate their use as novel materials in bioelectronics.

Characterization of poly(N-isopropylacrylamide)-nucleobase supramolecular complexes featuring bio-multiple hydrogen bonds

In this study we employed poly(N-isopropylacrylamide) (PNIPAAm) as a matrix that we hybridized with five different nucleobase units (adenine, thymine, uracil, guanine, cytosine) to generate PNIPAAm-nucleobase supramolecular complexes (PNSCs) stabilized through bio-multiple hydrogen bonds (BMHBs). These nucleobase units interacted with PNIPAAm through BMHBs of various strengths, leading to competition between the BMHBs and the intramolecular hydrogen bonds (HBs) of PNIPAAm. The changes in morphology, crystalline structure, and thermoresponsive behavior of PNIPAAm were related to the strength of its BMHBs with the nucleobases. The strengths of the BMHBs followed the order guanine > adenine > thymine > cytosine > uracil, as verified through analyses of Fourier transform infrared spectra, lower critical solution temperatures, and inter-association equilibrium constants. The PNSCs also exhibited remarkable improvements in conductivity upon the formation of BMHBs, which facilitated proton transport. The neat PNIPAAm film was an insulator, but it transformed into a semiconductor after hybridizing with the nucleobases. In particular, the resistivity of the PNIPAAm-guanine supramolecular complex decreased to 1.35 × 10(5) ohm cm. The resistivity of the PNIPAAm-cytosine supramolecular complex increased significantly from 5.83 × 10(6) to 3 × 10(8) ohm cm upon increasing the temperature from 40 to 50 °C, suggesting that this material might have applicability in thermo-sensing. The ability to significantly improve the conductivity of hydrogels through such a simple approach involving BMHBs might facilitate their use as novel materials in bioelectronics.