Isoprene Polymers

Abstract

Isoprene was first isolated from the pyrolysis products of natural rubber. The first preparation of polyisoprene was reported in 1879. In 1950, the goal of preparing synthetic cis 1,4‐polyisoprene as a counter part to natural rubber was achieved. Attention was then focused on commercial preparation of isoprene for polymerization use. Shortly after the discovery of stereospecific catalysts, the first commercial polyisoprene plant came on stream in 1959–1960 using a lithium catalyst. Isoprene is a reactive diene that undergoes cycloaddition, electrophilic, nucleophilic, free‐radical, and coordinated catalytic addition, and thermal dimerization. Information on the production of isoprene by naphtha cracking as well as the synthetic processes is detailed. Depending on the catalyst and conditions, isoprene may undergo 1,2,3,4, or 1,4 addition leading to several isomeric structures. Coordination catalysts, alkali metal catalysts, and Alfin catalysts are important for polymerization and are discussed. Chemical modification of polymers is a convenient way of altering physical and mechanical properties. Highly unsaturated polymers such as polyisoprene are easily modified because the olefinic bond is readily available. Their high reactivity with a variety of chemical substances offers advantages in chemical modification and vulcanization. However, reaction with oxygen and ozone causes degradation and loss of physical and mechanical properties. Synthetic polyisoprene is processed on conventional rubber machinery. Compounding technology is similar to that used for natural rubber. Typical formulations are given. A brief discussion of isoprene copolymers and 1,4‐ trans ‐polyisoprene is included. Isoprene is classified as a flammable liquid. It is a moderate irritant to the skin, eyes, and mucous membranes. The primary use for cis ‐1,4‐polyisoprene is in tires and tire products. It is also used, eg, in molded and mechanical goods, adhesives, belts, foam rubber, and elastic threads.. Automotive molded products and medical applications are typical. Trans ‐1,4‐Poyisoprene can be extracted, calendered, injection molded, and compression molded. It can be used in blends with other polymers. Its main use is in golf ball covers.

Recent Advances in Rare Earth Complexes Bearing Allyl Ligands and Their Reactivity towards Conjugated Dienes and Styrene Polymerization

“…Natural rubber extracted from the Hevea tree is composed predominantly of cis-units, whereas the one extracted from Gutta Percha is mainly trans-. Both cis-and trans-PI found numerous applications in the fields of adhesives, sports equipment, or the tire industry [25].…”

Stereochemistry of Polymerization

“…The anionic polymerization of 1,3-dienes yields different polymer structures depending on whether the propagating center is free or coordinated to a counterion [Morton, 1983;Quirk, 2002;Senyek, 1987;Tate and Bethea, 1985;Van Beylen et al, 1988;Young et al, 1984] Table 8-9 shows typical data for 1,3-butadiene and isoprene polymerizations. Polymerization of 1,3-butadiene in polar solvents, proceeding via the free anion and/or solvent-separated ion pair, favors 1,2-polymerization over 1,4-polymerization.…”

“…A variety of other initiators have been studied for the stereoselective polymerization of 1,3-dienes [Coates, 2000;Cooper, 1979;Endo and Hatakeyama, 2001;Ikai et al, 1999;Nath et al, 2002;Pasquon et al, 1989;Peluso et al, 1997;Porri and Giarrusso, 1989;Ricci et al, 1996;Senyek, 1987;Tate and Bethea, 1985;Visseaux et al, 2001]. Traditional Ziegler-Natta, metallocene, and other initiators yield remarkable results, surpassing the stereoselectivity by alkyllithium initiators.…”

A Study of the Catalytic Properties of Synthetic Aluminosilicates of Different Morphologies in Cracking Reactions of the Byproducts of Isoprene Synthesis

“…The petrochemical processes related to the production of isoprene for the production of synthetic rubbers (SRs), as a rule, are accompanied by the formation of a wide range of byproducts (BPs) (for example, dioxane alcohols, hydropyrans, and esters [1][2][3]). The latter are mainly used as fuel in waste heat boilers and are only partially processed technologically with the useful products being recycled [4].…”