Some remarks on the infrared analysis of polyisoprenes

Abstract

Several methods of infrared analysis of polyisoprenes have been described in the literature'-3); they all are potentially good for the determination of the isoprene units having 1,2 and 3,4 enchainment. However, unsatisfactory results and several difficulties are found for the determination of trans-1,4 and cis-1,4 units. The best results are obtained with the method proposed by BINDER and RAMSOW3), who suggested the use of the bands at 8.68 and 8.84 microns for the determination of trans-1,4 and cis-1,4 units respectively. Whereas these bands are clear and well detectable in hevea, balata, and in their artificial mixtures, they become hardly measurable in the various synthetic polyisoprenes, especially in those rich in 3,4 units.Unreliable results have been obtained for several samples because the total % found *) was too far from 100.Another method has been devided by cORISH4) who uses the near infrared spectrum. His method can only be used for the determination of the cis-1,4 units.In a careful study of the infrared spectrum of several polyisoprenes we have noticed that the methyl bending absorptions near 3.25 microns OCcur a t different positions with variable intensities, namely at 7.22 microns for the trans-1,4, a t 7.26 micronsfor the cis-1,4 and a t 7.265 for the 3,4 units.At the present state of our research no statement can be made for the 1,2 units because we did not yet succeed in obtaining polyisoprenes with a content of 1,2 units larger than some percent. C (cis) + C (tram) + C (3,4) C (conc. of solution)*) Total yo found = .loo. 250

High cis -1,4 polyisoprene or cis -1,4/3,4 binary polyisoprene synthesized using 2-(benzimidazolyl)-6-(1-(arylimino)ethyl)pyridine cobalt(II) dichlorides

“…The typical 1 H NMR chemical shifts and assignments for PI are as follows (CDCl 3 ; δ , ppm): 4.7–4.8 (CH 2 of 3,4 isoprene units), 5.0–5.1 (CH of 1,4 isoprene units), 1.74 (CH 3 of cis ‐1,4 units), 1.65 (CH 3 of trans ‐1,4 units). The typical 13 C NMR chemical shifts and assignments for PI are as follows (CDCl 3 ; δ , ppm): 32.56 (CH 2 of cis ‐1,4 units), 40.04 (CH 2 of trans ‐1,4 units), 38.36 (CH 2 of 3,4 units) . No resonance signals are observed at 5.9 and 1.65 ppm in the 1 H NMR spectra and there is also no signal at 40.04 ppm in the 13 C NMR spectra indicating that there are no 1,2 units and trans ‐1,4 units in the PIs.…”

Modification of polyisoprene‐block‐poly(vinyl trimethylsilane) block copolymers via hydrosilylation and hydrogenation, and their gas transport properties

“…FT‐IR spectra of H‐PI‐ b ‐PVTMS show the disappearance of characteristic bands of polyisoprene at 1716 cm −1 and 1376 cm −1 , which are assigned to CC stretching and the methyl group, respectively (Fig. ) …”

Effects of tris(pentafluorophenyl)borane on the activation of a metal alkyl‐free Ni‐based catalyst in the polymerization of 1,3‐butadiene

“…Conversion was calculated from the percentage by weight of the isolated polymer compared with the weight of the initially charged 1,3‐butadiene. The microstructure of the polybutadiene was measured in CS 2 solution by IR spectroscopy (Bio‐Rad, FTS 60‐A) according to the literature 17. Gel permeation chromatography data were obtained using a Viscotek TDA 300, employing connected Tosoh columns packed with polystyrene, G‐6000‐HXL, G‐5000‐HXL, G‐4000‐HXL, and G‐3000‐HXL, with a refractive index detector.…”

“…The microstructure of the polybutadiene was measured in CS 2 solution by IR spectroscopy (Bio-Rad, FTS 60-A) according to the literature. 17 Gel permeation chromatography data were obtained using a Viscotek TDA 300, employing connected Tosoh columns packed with polystyrene, G-6000-HXL, G-5000-HXL, G-4000-HXL, and G-3000-HXL, with a refractive index detector. THF was used as the solvent at a flow rate of 1.0 mL/min.…”