Synthesis and characterization of polymers having hydrogen-bonding functional groups

Abstract

This dissertation studies about the polymers having hydrogen-bonding functional groups which can form intra- or inter-molecular hydrogen-bondings depending on the environment. Self-assembly of polymer chains induced by the hydrogen-bond produced highly ordered structures with stimuli-responsiveness. First, novel triblock copolymers having self-complementary hydrogen-bonding (SHB) units based on dendritic benzamide were synthesized by using reversible addition-fragmentation transfer (RAFT) polymeriza-tion. These polymers formed noncovalent cross-linked supramolecular structures and showed an aggregation behavior by inter- and intramolecular interactions in chloroform or toluene. The polymers were found to have the both particle and network properties. The polymers formed nanoparticles, and the particle diameter and solution viscosity increases with increasing polymer concentration. Also well-ordered hexagonal microstructures were prepared by Breath Figure (BF) technique. Second, a series of polymers containing o-nitroanilide pendant groups were synthesized by RAFT poly-merization followed by post-modification. o-Nitroanilide group showed hydrogen-bonding mode changes de-pending on solution environment. In polar aprotic solvents such as dimethylsulfoxide and dimethylformamide, the amide moieties of o-nitroanilide make intermolecular hydrogen-bond while the intramolecular hydrogen bonding is favored in less polar solvents. Finally, a organogelator containing o-nitroanilide group and alkyl chain with diacetylene group was syn-thesized. This compound formed a transparent gel in nonpolar hydrocarbon solvents such as hexane, decane, and cyclohexane at concentration below 0.1 % (w/v). The gel underwent spontaneous morphology change from lamellar to fiber structure. Also crystallization of the organogelator was induced by physical stimuli. Molecular self-assembly behaviors and UV-responsive properties of the organogelator were studied.