Linear Polyisoprene Research Articles

Viscosity-temperature relationships for dilute solutions of linear and star polyisoprenes

Actual viscosities have been measured for dilute solutions of linear, 8- and 12-arm star polyisoprenes (PI) in benzene, a good solvent, over the range 25–60°. Viscosities were also measured for the three PI series in 1,4-dioxane over the range 35° (the theta condition for linear PI) to 59°. These experimental data were found to fit the empirical relationships suggested by Moore for flexible polymer chains.

X-Ray Diffraction Studies of Zwitterionic Associating Polymers

ABSTRACTWe have carried out x-ray scattering studies in melts of a series of linear polyisoprenes with highly polar sulfo-zwitterion groups at one end. The zwitterion end groups cause aggregation in good solvents for polyisoprene. The aggregation number depends strongly on the molecular weight of the polyisoprene tails and on the polarity of the solvent. Molecular mechanics simulations of the interactions between the zwitterion head groups suggest tubelike or diskline structures for the aggregates. Spherical structures are not energetically favorable. High resolution synchrotron x-ray scattering studies were carried out for six different (chain) molecular weights between 2000 and 23,000. For low molecular weights (between 2000 and 4000) a tubular structure is found with the tubes organized on a well-defined, two-dimensional triangular lattice with very large domain sizes >2000Å. A structural phase transition to a cubic (bcc) phase with long range order is observed to occur for molecular weights >10,000. The lattice spacing increase over the molecular range was between 95Å (for MW-2000) and 206Å (for MW-23,000). For the high molecular weight melts, annealing transforms the structure from (bcc) (with long range order) to an (fcc) disordered structure with short range order.

Measurement of chain dimensions in dilute polymer solutions: a light scattering and viscometric study of linear polyisoprene in cyclohexane

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMeasurement of chain dimensions in dilute polymer solutions: a light scattering and viscometric study of linear polyisoprene in cyclohexaneN. S. Davidson, L. J. Fetters, W. G. Funk, N. Hadjichristidis, and W. W. GraessleyCite this: Macromolecules 1987, 20, 10, 2614–2619Publication Date (Print):October 1, 1987Publication History Published online1 May 2002Published inissue 1 October 1987https://doi.org/10.1021/ma00176a048RIGHTS & PERMISSIONSArticle Views323Altmetric-Citations50LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (711 KB) Get e-Alerts Get e-Alerts

The softening of narrow-mesh network polymers and the mechanism of their deformability

It has been found that the experimental glass point of ebonites ( T g) based on polyisoprene corresponds to a network structure having crosslinks formed by mono-, di- and trisulphide groups. The sizes of the internodal fragments M c are substantially less than the segments of linear polyisoprene. Conclusions are made on the regional type of mobility in narrow-meshed networks, located in micro-domains containing a relatively high number of linked, partially mobile elements of the network structure.

Glass Transition Behavior of Polyisoprene: The Influence of Molecular Weight, Terminal Hydroxy Groups, Microstructure, and Chain Branching

Abstract The glass transition temperatures for a series of high-1,4 linear and star-branched polyisoprenes have been measured by differential scanning calorimetry. The Fox-Flory relation for the linear polyisoprenes was found to be Tg=Tg∞−1.76×104Mn−1. The influence of hydroxyl groups on Tg was also examined for low molecular weight (<2.2×104) polyisoprenes.

Polymer incompatibility study of a polystyrene network contaminated by linear polyisoprene chains

AbstractThe present paper deals with the study of anionic polystyrene (PS) networks containing linear polyisoprene (PI) chains. Special attention was devoted to the problem of the compatibility of such a system, depending on the molecular weight M̄w (weight average) or M̄n (number average) of the chains in the polymeric network and the number average molecular weight M̄n of the linear polyisoprene chains. For that purpose, three different methods were used: diffusion of a concentrated linear polyisoprene solution into the polymeric network, “in situ” polymerization of isoprene inside the polystyrene network, and crosslinking of “living” polystyrene in a linear polyisoprene solution.

NMR spectra of some model compounds of polyisoprene

Abstract1H, 2D, and 13C NMR spectra of five compounds modelling various types of monomer units addition in linear polyisoprene were investigated: 1,8‐hexadeuterio‐6‐methyl‐2‐trideuteriomethyl‐2,6‐octadiene (1), squalene (2), 4,7methyl‐3,7‐decadiene (3), 2,15‐bis(trideuteriomethyl)‐1,16‐hexadeuterio‐6,11‐dimethyl‐2,6,10,14‐hexadecatetraene (4), and 4,8‐dimethyl‐4,8‐dodecadiene (5). Compounds 1 and 3 were prepared for the first time. Analysis of the whole complex of spectral characteristics obtained made it possible to accomplish the assignment of lines in the carbon spectra of the compounds. It could be shown, that for linear bonding of isoprene units in case of the head‐to‐head type of addition sequence the methylene carbons in cis‐ and trans‐units absorb at 31,5 and 38,6ppm, respectively, and in case of tail‐to‐tail type of addition sequence the absorption is observed in the region of 28,4–28,8 ppm for both isomeric units.

13C n.m.r. determination of units formed by irregular addition in polyisoprene

13C n.m.r. spectroscopic data obtained for model compounds imitating regular and irregular addition of monomer units in linear polyisoprene are compared with the chemical shifts calculated using the empirical regularities found for the branched alkanes and alkenes and a good correlation is established. The validity of the results obtained was confirmed by investigation of the carbon spectra of hydrogenated and unhydrogenated polyisoprenes which contain chain fragments with irregular addition of units. Samples of hydrogenated polyisoprene are shown to give resonance lines that correspond to the methylene carbons of head-to-head and tail-to-tail addition and show chemical shifts at 34.62 ppm and 27.61 ppm, respectively. For the unhydrogenated polyisoprenes, the methylene carbons of trans- and cis-units in head-to-head addition were found to absorb at 38.6 ppm and 31.4 ppm, respectively, with those in the tail-to-tail addition of both isomers absorbing at 28.4–28.8 ppm. The latter findings offer a practical means of characterizing irregularities in polyisoprenes.

Pyrolysis gas chromatography of cyclopolyisoprene

Linear polyisoprene and polyisoprene containing cyclic structures in the chain both yield qualitatively identical mixtures of pyrolytic products. From the relative amount of isoprene formed during pyrolysis, the content of cyclic structures in the polymer was estimated. The results of this estimation are in agreement with high-resolution NMR analysis, while IR spectrometry gives values that are too high. In the chromatographic part of this paper, the homologous series of the 1-alkenes has been used for the calculation of retention indices.

Infrared examination of various polyisoprenes

AbstractThe infrared spectra of synthetic polyisoprenes have been used to obtain quantitative analyses for the various types of addition occurring in the polymers. It is found that the composition of polymers prepared in bulk and emulsion systems is, within experimental error, independent of specific catalyst and per cent conversion of monomer to polymer. The structure of these materials is affected by preparation temperature, increasing temperature leading to a slight increase in 3,4 addition and a large increase in cis 1,4 addition. Polymers prepared in solution with alfin and sodium catalysts show increased amounts of 3,4 addition at the expense of 1,4 addition. Polymers prepared with a cationic catalyst (BF3) are apparently not exclusively linear polyisoprenes.