Journal
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
Volume 59, Issue 2, Pages 735-739Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201912223
Keywords
conformational entropy; mechanical properties; poly(diketoenamine); rheology; vitrimers
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Funding
- Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under U.S. Department of Energy [DE-AC02-05CH11231]
- Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (BES)
- US Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program
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Control of equilibrium and non-equilibrium thermomechanical behavior of poly(diketoenamine) vitrimers is shown by incorporating linear polymer segments varying in molecular weight (MW) and conformational degrees of freedom into the dynamic covalent network. While increasing MW of linear segments yields a lower storage modulus at the rubbery plateau after softening above the glass transition (T-g), both T-g and the characteristic time of stress relaxation are independently governed by the conformational entropy of the embodied linear segments. Activation energies for bond exchange in the solid state are lower for networks incorporating flexible chains; the network topology freezing temperature decreases with increasing MW of flexible linear segments but increases with increasing MW of stiff segments. Vitrimer reconfigurability is therefore influenced not only by the energetics of bond exchange for a given network density, but also the entropy of polymer chains within the network.
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