Butyl Rubber. A New Hydrocarbon Product

Abstract

The present distinction between the thoughts expressed by the terms synthetic rubber and rubber synthesis is indicative of the changes in viewpoint on which current progress in the duplication of rubberlike properties is based. For almost fifty years after the discovery by Williams that isoprene is the fundamental structural unit of rubber, research was directed toward rubber synthesis. Bouchardat, Tilden, Wallach, Hoffman, Mathews, and Harries all made valuable contributions to the chemistry of rubberlike products from isoprene. That none of them accomplished the purpose of synthesizing rubber is an accepted fact. In the preparation of a rubberlike material from dimethylbutadiene, Kondakow departed from classical attempts at rubber synthesis, and laid the foundation for the first commercial “synthetic rubber”, the German wartime “methyl rubber”. The tradition that rubber properties were related to high unsaturation persisted, and has led to numerous theories of elastic behavior based on geometric structures resulting from unsaturated linkages. Whitby and Staudinger questioned the importance of unsaturation in determining rubberlike behavior, but encountered some difficulty in finding adequate support for this view, owing to the poor elastic properties of the practical examples available to them. Our studies on polymers of the simple monoölefins, which have been in progress for the past ten years, have led to some interesting conclusions in regard to this point. It was shown that high-molecular-weight linear polymers derived from simple olefins, such as the butylenes, possess a majority of the properties characteristic of rubber. Only the susceptibility to chemical action can definitely be attributed to the unsaturation of the natural rubber molecule. Physical properties which appear not to be intrinsically dependent on the carbon-double bond-carbon configuration are: tensile strength, elasticity, rebound, elastic memory, x-ray structure, mechanical orientation, electrical properties, and fractional solubility. It was, however, conclusively demonstrated that the saturated polymers are not capable of vulcanization in conventional manner.

Synthesis of carboxylated derivatives of poly(isobutylene-co-isoprene) by azide–alkyne “click” chemistry

“…Recovery yield = 0.87 g (90%), substitution level 4.0 mol% (100% conversion). 1 H NMR (300 MHz, CDCl3) δ ppm: 5.45 (1H, b, C=CH), 5.16 and 5.03 (2H of isoprene, s), 3.82-3.61 (3H, bm, CH-N3 and CH2-N3), 2.4-0.75 (aliphatic protons from isobutylene and isoprene units). Note: Caution must be applied in designing reactions with sodium azide since that compound is dangerous, particularly in large quantities.…”

“…Recovery yield = 0.89 g (82%), substitution level 4.0 mol% (100% conversion). 1 Synthesis of 5-hexenoic acid. Hydrogen peroxide (30% aqueous solution, 115 mL, 1 mol) was added to a stirred solution of cyclohexanone (49 g, 0.5 mol) in methanol (50 mL) over 30 min at 20-25 °C.…”

“…Yield = 14 g (70%). 1 Synthesis of 10-undecynoic acid. The procedure used was as described for 5-hexynoic acid.…”

“…Recovery yield for the reaction of IIR (1 mol% azidated isoprene units) with 10-undecynoic acid = 88%, substitution level 1 mol % (100% conversion). 1 Recovery yield for the reaction of IIR (1.9 mol% azidated isoprene units) with 10-undecynoic acid = 85%, substitution level 1.9 mol % (100% conversion). 1…”

“…Some of the characteristics of IIR include excellent impermeability to air, good electrical resistivity, excellent resistance to moisture, oxidation and heat, and good flex properties resulting from its low unsaturation level. [1][2][3][4] The range of properties displayed by IIR were further extended by introducing a low concentration of ionic moieties such as sulfonic acid groups bound along the polymer chains, to produce ionomers. 5 The synthesis of phosphonium and ammonium salts based on IIR has also been reported.…”