Synergies of Ionic and Hydrogen Bonding Interactions in Block Copolymers Synthesized via Nitroxide Mediated Polymerization

摘要

Hydrogen bonding enables the introduction of thermoreversible properties into macromolecules through the creation of specific non-covalent intermolecular interactions. Recent interest in hydrogen bonding in both supramolecular and macromolecular design has inspired numerous new explorations. We have investigated the effects of location of hydrogen bonding groups, topology, and the use of hydrogen bonding to influence rheological and mechanical performance. The strength of these interactions is a strong function of temperature, solvent, humidity and pH, thus allowing control of properties through a number of environmental parameters. The strength of hydrogen bonding associations is further tunable via structural parameters and association strengths range from DNA nucleobases, which have association constants near 100 M~(-1), to self-complementary ureidopyrimidone (UPy) groups, with association constants near 10~7 M~(-1). In contrast to hydrogen bonding interactions, ionic interactions are less specific or directional, but offer higher enthalpies of association, leading to materials with impressive mechanical properties, yet with higher melt viscosities that impact processability.