High Glass‐Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
Résumé
Differential scanning calorimetry of high molar mass poly(4-vinylphenylboronic acid, pinacol ester)s evidenced unusual reactive events above 120°C, resulting in a high glass transition temperature of 220°C. We hypothesize a ring-opening reactivity of pinacol boronates involving a nucleophilic attack on the sp 2 boron and subsequent bridging by interconnected pinacol moieties to form a densely crosslinked network with high-Tg. FTIR, solid-state NMR investigations and rheology studies on the polymer as well as double-tagging analyses on molecular model structures and theoretical calculations further support this hypothesis and indicate an entropy-driven ring opening inducing crosslinking. When diluted in an apolar solvent such as toluene, the polymer network can be resolubilized via ring closing thus recovering the entropically-favoured linear chains featuring cyclic boronate esters. The introduction of boron reactivity in polymer chains may open a path to a new class of dynamic polymer networks with uncommon and exciting thermodynamics.
Domaines
Polymères
Origine : Fichiers produits par l'(les) auteur(s)
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