Sequence distribution of 1,4 and 3,4 units in polyisoprenes

Abstract

The 13C‐NMR spectra of hydrogenated polyisoprenes were investigated. Polyisoprenes containing various ratios of 1,4 and 3,4 units were prepared with n‐BuLi/Et2O and were hydrogenated by using p‐toluenesulfonylhydrazide. 13C‐NMR signals of the hydrogenated polymers were assigned for the triad sequences magnified image arising respectively from the 1, 4 and 3, 4 units of polyisoprenes. On the basis of these assignments it was confirmed that 1,4 and 3,4 units were randomly distributed in the polyisoprenes prepared with n‐BuLi and that these polymers did not contain appreciable amounts of head‐to‐head or tail‐to‐tail 1,4 linkages.

Rare-Earth-Metal Allyl Complexes Supported by the [2-(N,N-Dimethylamino)ethyl]tetramethylcyclopentadienyl Ligand: Structural Characterization, Reactivity, and Isoprene Polymerization

“…Depending on the amount and tacticity of the 3,4-units, distinct NMR shifts of adjacent isoprene units are observed, making structure analysis a challenging task. 64 On the other hand, systematic incorporation of 3,4-units has been proven to influence the physicochemical properties of such rubbers, as has been shown for the increase in wet skid resistance coupled with balanced abrasion and rolling resistance properties of produced tire treads. 65 However, the majority of publications on the structural NMR analysis of polyisoprenes have dealt with the incorporation of 3,4-units in polymers with pronounced cis-1,4-microstructure.…”

NMR Characterization of a Hydrogenated Hydroxytelechelic Polyisoprene

“…Only C-atoms of the 3,4-unit exhibit large differences between the observed and calculated chemical shift values. According to Tanaka et al [13] , this result arises from the steric effect of the pendant isopropyl group of this kind of unit. Other specific isolated signals (i, k, m, u, v) were also assigned using calculated chemical shift values and model compounds.…”

“…Hydrogenated polyisoprenes containing 1,4-, 1,2-, and 3,4-units exhibit complicated 13 C NMR resonances arising from different types of linkages ( Figure 5). According to the PIHT microstructure, the polymer is highly 1,4 constituted, having 1,2-, and 3,4-units randomly distributed along the polymer backbone [7] .…”

“…Keywords: Hydrogenated polyisoprene; Microstructure; 1 H and 13 C NMR Low-molecular-weight hydroxy-terminated polyolefins are inert polyols that can be used to prepare high-molecular-weight polyurethanes. The inertness of these soft segments contributes to the enhancement of solvent resistance and mechanical properties of the resulting polymers as compared to the corresponding unsaturated homologues [1][2][3][4] , and the polymers exhibit very good thermal stability for electrical insulating 301 applications [5] .…”

“…The hydroxyl average functionality (f n OH $ 2.2 AE 0.1) and the hydrogenation rate ($ 95%) of this low molar mass polyol were calculated. 13 C NMR signals arising from 1,4-, 1,2-, and 3,4-units were assigned, as well as head-to-head and tail-to-tail linkages of the 1,4-units. Four main primary alcoholic end groups were identified and the presence of tertiary alcohol was confirmed.…”