Poly-2,3-dimethyl Butadiene

Hydrogenated poly-2,3-dimethyl butadiene has strong IR absorption at 9.0 pm, confirming a head-to-head configuration of two propylene units in the hydrogenated polymer  

The following structure for the unhydrogenated polymer is shown below H CHj CH3 H 

For dimers, many regioiosmeric configurations are possible. Polybutadiene unsaturation occurs in three forms trans-, , c/s-1,4 and vinyl-1,2  

No opportunity for regioisomerism exists in the cis and trans-, 4 configurations, but does for vinyl-1,2 unsaturation  

During World War I, poly(dimethyl butadiene) (methyl rubber) was manufactured as a substitute for the natural rubber that the Central Powers lacked when the war ended, its production was curtailed because of its relatively poor properties and high cost. 2,3-Dimethyl butadiene is produced from acetone via pinnacol  

H-type poly(dimethyl butadiene) is obtained by letting the monomer stand for three months in ventilated metal drums. The white, solid crystalline 

Is found in amorphous ethylene-propylene alternating copolymers and in polybutene-2-ethylene alternating copolymer and in hydrogenated poly 2,3-dimethyl butadiene  

Ethylene-propylene Polybutene-1 -ethylene Hydrogenated poly-2,3- 

The infrared spectrum of amorphous alternating polybutene-l-ethylene copolymer shows absorptions at 13.3 pm, characteristic of methylene sequences of two units and at 9 pm characteristic of the structure  

---

Blends involving synthetic polymers were not developed until the twentieth century. The first synthetic high molecular weight polymers were developed by Farbenfabriken Bayer in the first two decades of the twentieth century. These were the first synthetic elastomers. Poly(dimethyl butadiene), widely used in Germany, was used in World War I (Section 1.3.1). 

As described in Section 1.1, the first commercial polymers, which were naturally occurring, were polyisoprenes (natural rubber and gutta-percha) and subsequently cellulose derivatives. From the early twentieth century, various totally synthetic polymers were introduced. Farbenfabrrken Bayer introduced bulk polymerized totally synthetic elastomers in 1910. Poly(dimethyl butadiene) synthetic rubber was produced commercially by Bayer in Leverkusen during World War I. The 1920s saw the commercial development of polystyrene (PS) and poly(vinyl chloride) (PVC). In 1934, the IG Farbenindustrie (a combine of Bayer, BASF, Floechst, and other firms) began to commercially manufacture butadiene-acrylonitrile copolymer (N BR) as an oil resistant rubber and in 1937 butadiene-styrene copolymer (SBR) intended for pneumatic tires. 

Figure 15, Differential scanning calorimetry of cis-poly-(dimethyl butadiene),...

Figure 16. H NMR spectrum of cis-poly(dimethyl butadiene) at 90 MHz in trichlorobenzene solution at 125 C. 

Siloxane elastomers present an attractive alternative to the butadiene acrylonitrile elastomers most often used for epoxy modification. Poly(dimethyl siloxanes) exhibit glass transition temperatures well below those of butadiene acrylonitrile modifiers (minimum —123 °C vs. about —40 °C) and also display very good thermal stability13, 14). Other favorable and potentially useful attributes include good weatherability, oxidative stability, and moisture resistance. Finally, the non-polar nature and low surface energy of poly(dimethyl siloxanes) constitute a thermodynamic driving force... 

Gas chromatographic analysis (0.53-mm id x 10 m poly (dimethyl silicone) fused silica column, temperature programmed from 140°C to 220°C) indicates that this product is 98% pure, with <1% 3-methyl-1-phenyl-1,3-butadiene and 1-2% of a less volatile, unidentified component. The checkers could obtain a very pure product by normal vacuum distillation. They found the impurities to be higher boiling compounds. 

Early studies on the homopolymerization of E-l,3-pentadiene yielded polymers with a high cis-1,4-content and an isotactic structure, whereas E-2-methyl-l,3-pentadiene resulted in a polymer with a mixed czs-1,4/transit-structure [487-492]. Investigations on the polymerization of E-1,3-pentadiene with the system NdN/TIBA/DEAC partially support these findings as a poly(l,3-pentadiene) with a cis- 1,4-threo-disyndiotactic structure was obtained [492]. A somewhat lower cis- 1,4-content of 70% was obtained when the polymerization of E-l,3-pentadiene was catalyzed by (CF3COO)2NdCl/TEA [493,494]. When 2,3-Dimethyl-1,3-butadiene is polymerized with the catalyst NdN/TIBA/EtAlC the resulting poly(2,3-dimethyl-butadiene) predominantly contains cis-1,4-units [495,496]. 

Poly(isobutylene) dicarboxylic acid was prepared by oxidation of the copolymer of isobutylene with a diene 53,54). The most efficient oxidizing agent was the system KMn04-periodic acid. Oxidation of a copolymer of isobutylene and 2,3-dimethyl-butadiene afforded a polymeric bis-ketone54). 

Abbreviations ABS, acrylonitrile-butadiene-styrene terpolymer PB, polybutadiene PC, polycarbonate PS, polystyrene PET, poly(ethylene terephthalate) PBT, poly(butylene terephthalate) SBR, styrene-butadiene rubber TEA, V-trifluoroacetylated polyamides PMMA, poly(methyl methacrylate) SAN, poly(styrene-acrylonitrile) SBS, poly(styrene-butadiene-styrene) PVA, poly(vinyl acetate) PVB, poly(vinyl butyral) PVC, poly(vinyl chloride) PDMS, poly(dimethyl siloxane) PE, polyethylene EVA, poly(ethylene-vinyl acetate) UHMWPE, ultra high molecular weight polyethylene PP, polypropylene. 

Figure 7.9. Dependence of the melt viscosity rj of polymers on the parameter Zw (see text) at 021 0. For easier comparison, the 17 values of the different types of polymer have all been multiplied by a constant factor of C. PDMS, Poly(dimethyl siloxane) PIB, poly(isobutylene) PB, poly(butadiene) PMMA, poly(methyl methacrylate) PVAC, poly(vinyl acetate) PS, poly(styrene) (after T. G. Fox).

Synthetic polymers are relatively recently introduced materials. The natural fiber wool has already been used since antiquity, but the first completely synthetic fibers have only been in use since 1940. Iron has been known as a working material for thousands of years, but the oldest thermoset, phenolic resin, has only been known since 1906, and the oldest completely synthetic thermoplast, poly(vinyl chloride-co-acetate), has only been commercially produced since 1928. Large-scale application of elastomers has only been known since the beginning of the 19th century, when natural rubber was used, but the first commercial synthesis of a completely synthetic elastomer, poly(2,3-dimethyl butadiene), was only made in 1916. Since this time, the commercial production of thermoplasts, thermosets, chemical fibers, and synthetic rubbers has increased strongly (Figure 33-2). 

Poly(2,3-dimethyl butadiene) n. Avery elastic synthetic rubber, the monomer being made by conversion of acetone via pinacol to 2,3-dimethyl-butadiene (See image). 

Examples of typical elastomers include natural rubber, butyl rubber, poly(dimethyl siloxane), polyethyl acrylate, styrene-butadiene copolymer, and ethylene-propylene copolymer. Some polymers are not elastomers under normal... 

Polyisoprene polybutadiene poly(2, 3-dimethyl-butadiene) Polystyrene... 

---