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

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

Synthesis and Characterization of Comb and Centipede Multigraft Copolymers P<i>n</i>BA‑<i>g</i>‑PS with High Molecular Weight Using Miniemulsion Polymerization

Comb and centipede multigraft copolymers, poly­(<i>n</i>-butyl acrylate)-<i>g</i>-polystyrene (P<i>n</i>BA-<i>g</i>-PS) with P<i>n</i>BA backbones and PS side chains, were synthesized via high-vacuum anionic polymerization and miniemulsion polymerization. Single-tailed and double-tailed PS macromonomers were synthesized by anionic polymerization and Steglich esterification. Subsequently, the copolymerization of each macromonomer and <i>n</i>BA was carried out in miniemulsion, and multigraft copolymers were obtained. The latex particles of multigraft copolymers were characterized using dynamic light scattering. The molecular weights of macromonomers and multigraft copolymers were analyzed by size exclusion chromatography. Moreover, the molecular weights and structures of macromonomers were investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and ¹H nuclear magnetic resonance spectroscopy. The weight contents of PS in comb and centipede multigraft copolymers were calculated by ¹H nuclear magnetic resonance spectroscopy. The thermal properties of multigraft copolymers were characterized by thermogravimetric analysis and differential scanning calorimetry. The microphase separation of multigraft copolymers was observed by atomic force microscopy and transmission electronic microscopy. Rheological measurements showed that comb and centipede multigraft copolymers have elastic properties when the weight content of PS side chains is 26–32 wt %. Centipede multigraft copolymers possess better elastic properties than comb multigraft copolymers with the similar weight content of PS. These findings are similar to previous results on poly­(isoprene-<i>g</i>-polystyrene) comb and centipede copolymers made by anionic polymerization