Structure−Property relationships in nanocomposites based on cyanate ester resins and 1-heptyl pyridinium tetrafluoroborate ionic liquid

• Published in: Polymer (Guilford) Vol. 148; pp. 14 - 26
• Main Authors: Vashchuk, A., Rios de Anda, A., Starostenko, O., Grigoryeva, O., Sotta, P., Rogalsky, S., Smertenko, P., Fainleib, A., Grande, D.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 18-07-2018; Elsevier BV; Elsevier
• Subjects: Chemical Sciences; Crosslinking; Cyanates; Dicyanates; Dielectrics; High temperature; Ionic liquids; Kinetics; Material chemistry; Nanocomposites; Phase separation; Phenols; Photosensitivity; Polymers; Pyridinium; Reaction kinetics; Reaction mechanisms; Resins; Spectroscopy; Thermal degradation; Thermal stability; Thermosetting polymers; Nanocomposites; Ionic liquids; Thermosetting polymers
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2018.06.015

Novel thermosetting systems based on cyanate ester resins (CERs) have been created through the polycyclotrimerization reaction of dicyanate ester of bisphenol E (DCBE) in the presence of different amounts of 1-heptyl pyridinium tetrafluoroborate [HPyr][BF4] Ionic Liquid (IL). A significant accelerating effect on the curing kinetics of DCBE was found by FTIR analysis. The reaction mechanism for the [HPyr][BF4]-catalyzed polycyclotrimerization of DCBE was newly proposed via the formation of a [CN]δ+–[HPyr]δ− complex as a key intermediate. Structure–properties relationships for the thermostable CER/IL networks were investigated by using DSC, DMTA, dielectric spectroscopy, tensile testing, quasi-dc measurements (I-V characteristics), and TGA. All the nanocomposites showed excellent thermal stability up to 300 °C, indicating the formation of a densely crosslinked network even at high IL content (40 wt%), and they could be used at high temperatures above their Tg without significant thermal degradation. Nanoscale phase separation led to the creation of ionic channels within the CER matrix to ensure photosensitivity properties.
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•[HPyr][BF4] acts both as a catalyst and a structure-directing agent increasing free volume in CER-based nanocomposites.•Nanoscale phase separation leads to the creation of ionic channels within the CER matrix to ensure photosensitivity properties.•Nanocomposite materials can be used at high temperatures above their Tg without significant thermal degradation.