Synthesis and Characterization of Ureidopyrimidone Telechelics by CuAAC “Click” Reaction: Effect of <i>T</i>_g and Polarity

Abstract

Telechelic oligomers functionalized with 2-ureido-4­[1H]-pyrimidone (UPy), a quadruple hydrogen bonding group, have been synthesized using a combination of atom-transfer radical polymerization and click reaction. Ureidopyrimidone (UPy) synthons with propargyl and azide functionality were used for clicking with azido and propargyl telechelic oligomers, respectively. The effect of triazole linker and types of oligomers differing in Tg and polarity, such as poly­(n-butyl acrylate) (PnBA), polystyrene (PS), and polybutadiene (PBd) on UPy hydrogen bonding have been examined. High solution viscosity and deviation from the normal terminal relaxation in melt state were observed, suggesting the presence of UPy aggregates that are in equilibrium between linear and network polymers. Differential scanning calorimetry studies confirm dissociation of UPy aggregates as an endothermic peak for PBd system, whereas the high Tg and polar polymers (PS and PnBA) had no such peaks associated with Tm indicating the significance of the polymer chain dynamics in supramolecular hydrogen bonding. The triazole linker interferes with the UPy association and reduces the sizes of hydrogen-bonded UPy aggregates and thereby improves the physical property of supramolecular polymers