¹³C NMR spectroscopic study of epoxidized 1,4‐polyisoprene and 1,4‐polybutadiene

Abstract

Partly epoxidized cis‐ and trans‐1,4‐polyisoprenes and cis‐and trans‐1,4‐polybutadienes were prepared, and their 13C NMR spectra examined. All the prominent resonances in the spectra of the epoxidized polymers were assigned by using lanthanide shift reagent and off‐resonance decoupling experiments. A 13C NMR method of quantitative assessment of the epoxide content was developed following determination of relative spin‐lattice relaxation time (T1) and nuclear Overhauser effect (NOE) parameters of the various carbons in the epoxidized polyisoprenes and polybutadienes.

Cloisite 15Aº nanoclay as an effective PTC for the epoxidation of hydroxyl terminated polybutadiene (HTPB)

“…In HTPB, cis and trans double bonds had their signals at 129 ppm, but as the epoxidation reaction progressed, additional signals appeared at 56 ppm and 58 ppm, which were pertinent to cis and trans epoxy, respectively. The obtained results are similar to the results obtained by Gemmer and Golub [29] . Focusing on the 114 ppm and 141 ppm regions in the 13 CNMR spectra, we found that vinyl carbons remained unchanged due to their low electron density.…”

“…These signals were respectively, shifted to about 2.9, 2.7, 2.5, and 3.0 ppm in the epoxidized HTPB. Of course, we did not observe vinyl epoxy in the 1 HNMR, which was due to the lower reactivity of vinyl bonds in comparison to cis and trans double bonds [29] . This indicates that vinyl double bonds are rarely epoxidized.…”

“…According to our obtained results from spectra, the findings are similar to previously reported data by elsewhere [28] . In addition, the assignment of cis, trans and vinyl epoxy groups in the epoxidized products were based on the data reported by Gemmer and Golub [29] and Zuchowska [30] . A comparison of epoxidized and unepoxidized HTPB in the 1 HNMR spectra showed that signals at 5.3 ppm, 5.4 ppm, 4.9 and 5.6 were pertained to cis, trans, and vinyl double bonds, respectively.…”

Thermal rearrangements of polybutadienes with different vinyl contents

“…Note added in proo[: An attractive alternative to reaction (5) which can account for the loss of vinyls and the accompanying formation of methyls, with no apparent loss of vinylenes, in polybutadienes with low vinyl contents, is reaction (6).…”

Chemoselective epoxidation of hydroxyl-terminated polybutadiene (HTPB) using in-situ generated dimethyl dioxirane (DMD)

“…The assigning of cis, trans and vinyl epoxy groups was based on data reported by Akcelrud et al [5], Zuchowska [9] and Gemmer and Golub [23]. By the comparison of the peak areas for epoxy protons at 2.7 and 3.0 ppm with the unreacted one, it was found that the absorption at 2.7 ppm was related to the trans, whereas the one at 3.0 ppm was related to the cis epoxy protons, respectively (Fig.…”