33S nuclear quadrupole resonance study of dibenzyl disulfide toward understanding of cross-linked structures in rubber

Kazuhiko Yamada; Kazuko Nakazono; Toshihiro Yoshie; Masashi Fukuchi; Takehiro Kitaura; Toshikazu Takata

doi:10.1016/j.ssnmr.2019.05.011

³³S nuclear quadrupole resonance study of dibenzyl disulfide toward understanding of cross-linked structures in rubber

Solid State Nucl Magn Reson. 2019 Sep:101:110-115. doi: 10.1016/j.ssnmr.2019.05.011. Epub 2019 May 30.

Authors

Kazuhiko Yamada¹, Kazuko Nakazono², Toshihiro Yoshie², Masashi Fukuchi³, Takehiro Kitaura³, Toshikazu Takata²

Affiliations

¹ Interdisciplinary Science Unit, Multidisciplinary Sciences Cluster, Research and Education Faculty, Kochi University, Nankoku City, Kochi, 783-8505, Japan. Electronic address: kyamada@kochi-u.ac.jp.
² School of Materials and Chemical Technology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan.
³ Sumitomo Rubber Industries Ltd, 1-1, 2-chome, Tsutsui-cho, Chuo-ku, Kobe, 651-0071, Japan.

PMID: 31181414
DOI: 10.1016/j.ssnmr.2019.05.011

Abstract

Experimental and theoretical investigations of a sulfur-33 electric-field-gradient (EFG) tensor of disulfide bonds in ³³S-labled dibenzyl disulfide have been presented. Temperature dependence of quadrupolar frequencies, ν_Q, is observed in the temperature range between 80 and 280 K, in which single peaks appear in all the ³³S nuclear quadrupole resonance (NQR) spectra. Analysis of nutation echo ³³S NQR spectra at 200 K yields the quadrupolar coupling constant, C_Q value, of 46.8(6) MHz and the asymmetry parameter, η_Q, of 0.48(7). The orientation of the ³³S EFG tensor of the disulfide is obtained by quantum chemical calculations: the largest EFG tensor component, V_ZZ, is approximately perpendicular to the molecular plane (C-S-S), and the smallest component, V_XX, is approximately 41° off the C-S bond. Extensive quantum chemical calculations are systematically performed to investigate dependences of ³³S EFG tensors on changes of torsion angles in disulfide and trisulfide bonds, indicating that analysis of ν_Q and C_Q values potentially makes it possible to assign the secondary structures of cross-linking in a rubber.

Keywords: Cross-linked structure; Dibenzyl disulfide; Rubber; Sulfur-33 NQR.