A fourier transform infrared and nuclear magnetic resonance study of cyclized natural rubber

Abstract

Fourier transform infrared (FTIR), ' H NMR, and ',C NMR have been used to characterize the structure of natural rubber cyclized with p-toluenesulfonic acid. The samples studied were only partially cyclized. The cyclized portions contained both mobile and rigid domains. Crosslinking occurred during the cyclization reaction. The cyclized samples showed a distribution of functionalities including some oxidation products. All three types of olefinic segmented end groups were formed during cyclization (di-, tri-, and tetrasubstituted olefins). The loss of the exocyclic species leads to the formation of cross-linked networks.

Cationic cyclization of purified natural rubber in latex form with a trimethylsilyl triflate as a novel catalyst

“…Two spectra regions were observed to undergo changes during cyclization; the carbon-carbon double bond stretching modes at 1600 cm À1 , the CH 2 deformation and CÀ ÀC stretching mode region at 900-1200 cm À1 , and the CÀ ÀH bending mode region at 800-900 cm À1 . 10,21 The band at 1664 cm À1 was due to the cis-1,4 carbon-carbon double bond stretching mode. This observation indicates that cyclization was incomplete.…”

“…Patterson and Koenig 10 have investigated the structure of cyclized NR obtained from p-toluenesulfonic acid in toluene solution by FTIR and NMR spectroscopies. They concluded that the cyclized portions contained both mobile and rigid domains due to crosslinking during the cyclization reaction.…”

Preparation of polymer electrolyte membrane with nanomatrix channel through sulfonation of natural rubber grafted with polystyrene

“…The broad signals appeared due to the presence of complicated structural units in the polymer after sulfonation of the DPNR. According to a previous study, the overlapping broad signals in the aliphatic region ranging from 10 ppm to 80 ppm were assigned to methyl and methylene carbons of cyclized cis-1,4-isoprene units, and that in the olefinic region ranging from 110 ppm to 155 ppm were assigned to the olefinic methine and trisubstituted carbons [14]. Thus, the broad signals in the 13 C CP/MAS NMR spectrum for the SDPNR-graft-PS were assigned to the cyclized cis-1,4-isoprene units and the sulfonated PS units.…”

Use of trifluoromethanesulfonic acid as catalyst for the cyclization of polyisoprene

“…The available proton adds to a double bond, according to Markownikoff's rule, to form a carbenium ion, and subsequently, the carbenium ion attacks the adjacent olefinic carbons, which leads to a cyclic molecular structure after deprotonation, as illustrated in Scheme 1. 5 Harita et al illustrated that fluorine-contained substituted sulfonic acid compounds can be applied as catalyst for the cyclization of conjugated diene polymers. 6 These sulfonic acids are represented by the formula:…”

“…[3][4][5] The acid-catalyzed cyclization reaction is a cationic reaction. The available proton adds to a double bond, according to Markownikoff's rule, to form a carbenium ion, and subsequently, the carbenium ion attacks the adjacent olefinic carbons, which leads to a cyclic molecular structure after deprotonation, as illustrated in Scheme 1.…”