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High Glass‐Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
Author(s) -
Brunet Juliette,
Collas Franck,
Humbert Matthieu,
Perrin Lionel,
Brunel Fabrice,
Lacôte Emmanuel,
Montarnal Damien,
Raynaud Jean
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201904559
Subject(s) - pinacol , glass transition , differential scanning calorimetry , polymer , chemistry , polymer chemistry , ring (chemistry) , toluene , organic chemistry , catalysis , thermodynamics , physics
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. A reversible ring‐opening reactivity of pinacol boronates is proposed, involving a nucleophilic attack on the sp 2 boron and subsequent bridging between boron atoms by interconnected pinacol moieties to form a densely crosslinked network with high T g . 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 a 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 favored linear chains featuring cyclic boronate esters.