Imidazole-accelerated crosslinking of epoxidized natural rubber by dicarboxylic acids: a mechanistic investigation using NMR spectroscopyElectronic supplementary information (ESI) available: S1. Compared DSC thermograms of pure DA and ENR50/DA blends, before and after curing. S2. Compared DSC thermograms of pure DA/DMI salt and ENR50/DA/DMI blends, before and after curing. S3. Comparison of 1H 13C CP/MAS/DD NMR spectra of ENR/DA and ENR/DA/DMI blends before curing. See DOI: 10.1039/c2py00591c

• Main Authors: Pire, Myriam, Lorthioir, Cdric, Oikonomou, Evdokia K, Norvez, Sophie, Iliopoulos, Ilias, Le Rossignol, Benot, Leibler, Ludwik
• Format: Journal Article
• Language: English
• Published: 06.03.2012
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/c2py00591c

The crosslinking of epoxidized natural rubber with dodecanedioic acid and the mechanism of its acceleration by 1,2-dimethylimidazole (DMI) are investigated using nuclear magnetic resonance spectroscopy. Solid-state NMR experiments ( 1 H, 1 H 13 C cross-polarization and 13 C direct polarization) are used to analyse crosslinked samples, whereas 13 C solution NMR provides information about liquid epoxidized rubber species. 13 C solid-state NMR demonstrates the ester nature of the crosslinks, and confirms that DMI acts through the formation of imidazolium dicarboxylate species, well dispersed in the elastomeric matrix. After synthesis of a low molecular weight epoxidized rubber and subsequent reaction with a monofunctional carboxylic acid in the presence of DMI, a solution NMR study reveals that the imidazolium dicarboxylate would react preferentially at the less substituted side of the epoxy site. Solid-state NMR spectroscopy is used to investigate the crosslinking mechanism of epoxidized natural rubber by dicarboxylic acids.