The addition reaction of alcohols and aromatic carbodiimides and its application to produce thermo-reversible polymer networks
The addition reaction of primary alcohols onto aromatic carbodiimides giving iso-ureas was studied in bulk at various temperatures. A side reaction at 60 °C was found to occur between carbodiimide and iso-urea yielding N,N′-substituted polyguanidine oligomers. The occurrence of this side reaction co...
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Published in | Polymer (Guilford) Vol. 305; p. 127176 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Elsevier Ltd
12.06.2024
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Subjects | |
Online Access | Get full text |
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Summary: | The addition reaction of primary alcohols onto aromatic carbodiimides giving iso-ureas was studied in bulk at various temperatures. A side reaction at 60 °C was found to occur between carbodiimide and iso-urea yielding N,N′-substituted polyguanidine oligomers. The occurrence of this side reaction coincides with a reduced conversion of the alcohol; the carbodiimide was always fully converted to either iso-urea or polyguanidine. The formation of the polyguanidine was reversible at higher temperatures to reform iso-urea and carbodiimide. The latter reaction was complete at about 130 °C. The thermo-reversibility of the guanidine bond was utilized to produce thermo-reversible self-healing polymer networks by reaction of polyether diol and a 1.5 to 2-fold molar excess of aromatic biscarbodiimide. The materials were soft and elastic and showed a glass transition at −60 °C. The guanidine linkages in the polymers started to unzip above 60 °C as was indicated by a drop in the E-modulus, at about 130 °C sufficient guanidine crosslinks had unzipped to provide the polymer liquid-like properties. The guanidine crosslinks were reformed after cooling to ambient temperature giving back the polymer network.
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•The reaction of carbodiimide and hydroxyl gave stable isourea bonds.•Using excess carbodiimide yielded thermo-reversible guanidine linkages.•Reacting polyol with excess bis-carbodiimide provided crosslinked polymer.•The crosslinks were stable below 60 °C and unzipped above 130 °C.•The thermosetting polymers showed thermally self-healable properties. |
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ISSN: | 0032-3861 1873-2291 |
DOI: | 10.1016/j.polymer.2024.127176 |