Preparation and properties of dendritic polyamides-poly(4-vinylpyridine) complexes via multiple hydrogen bonding

摘要

Recently, complexes composed of non-covalent interactions, such as hydrogen bond, hydrophobic interaction, and coordinate bond have been attracted much attention as new soft materials. Since the non-covalent interactions are much weaker than covalent bonds, properties of the complexes may be dynamically changed by formation or cleavage of the non-covalent interaction by external stimuli.Hydrogen bond is one of the most important non-covalent interactions in chemical and biological systems. Directionality and reversibility of hydrogen bonds are invaluable tools in designing complex organized structure. Kato et al. reported hydrogen bonded liquid crystals composed of side-chain polymers. The hydrogen bond between carboxylic acid and pyridine affected mesophase-isotropic transition temperature and stabilized liquid crystalline phase. Griffin et al. described polymeric networks prepared from two different small molecules or oligomeric components which have functional groups of hydrogen donor and hydrogen acceptor. Stable complexes could not be isolated due to the weakness of single or double hydrogen bonds. Recently, Meijer et al. reported the stable complexes formed by quadruple hydrogen bond between 2-ureido-4[1H]-pyrimidone (UPy) units attached to a hexamethylene spacer, m-xylylene spacer, oligo(ethylene glycol), oligo(ethylene glycol-co-propylene glycol) copolymer, and poly(dimethylsiloxane). These non-covalent bonded molecules showed polymer-like properties, which includes shear thinning, viscoelastic behavior, and glass transition behavior. It is clear that multiple hydrogen bondings are essential for the formation of stable complexes. It is well-known that dendrons and dendrimers have unique properties such as low viscosity, high solubility, and multi-functionality derived from their unique architecture. If end groups of dendrimers are utilized for multiple hydrogen bondings, novel stable complexes by hydrogen bonding could be prepared. In this work, we report the preparation and properties of the complexes from various dendritic polyamides and poly(4-vinylpyridine) (P4VP) via multiple hydrogen bondings.