Poly l,2-butadiene

FIGURE 12.8 Idealized structures for the synthesis of carbonlike materials from poly(l,2-butadiene). 

Otsuka et al. (110, 112) studied the polymerization of butadiene in the presence of an aged Co2(CO)8/2 MoC15 catalyst. The product obtained was predominantly an atactic poly(l,2-butadiene), the 1,2-structure being favored by low reaction temperature (e.g., at 40° C, 97% 1,2 at 30° C, > 99% 1,2). Similar experiments with a Ni(CO)4/MoCl5 catalyst yielded a polymer with 85% cis- 1,4-structure. The results of Otsuka et al. have been confirmed by Babitski and co-workers (8), who studied the polymerization of butadiene by a large number of binary catalysts, based on transition metal halide, transition metal carbonyl combinations. These systems are of interest as further examples of alkyl-free coordination polymerization catalysts for dienes (9, 15a, 109). Little is known of the origins of stereospecificity of these reactions. 

The group of Abetz [77] used polystyrene-fcZocA -poly(l,2-butadiene)-block-polyitert-hutyl methacrylate) triblock copolymers with partially hydrolyzed poly(tert-butyl methacrylate) blocks, together with polystyrene-... 

This method was extended to the synthesis of PBd stars having more than 200 arms.43 Low molecular weight linear and star poly(l,2-butadiene) with 18 arms was extensively hydrosilylated with methyldi-chlorosilane and used as linking agents to prepare multiarm PBd stars, as shown in Scheme 7. The... 

In macromolecular chemistry helically wound carbon chains are well known. In isotactic polypropylene (Fig. 6) the methyl groups are arranged on a helix. Some other chiral polymers form helices, like polymethylmethacrylate, polytriphenylmethyl-methacrylate poly-l,2-butadiene and poly-tert-butylethylene oxide... 

Kim, E.G., Misra, S., Mattice, W.L. Atomistic models of amorphous polybutadienes. 2. Poly(1.4-trans-butadiene), poly(l,2-butadiene), and a random copolymer of 1,4-trans-butadiene, 1,4-cis-butadiene, and 1,2-butadiene. Macromolecules 26, 3424-3431 (1993)... 

The fully extended planar zigzag trcms conformation) is the minimum energy conformation for an isolated section of polyethylene or paraffin hydrocarbon. The energy of the trans conformation is about 800 cal/mol less than that of the gauche form. Consequently, the trans form is favored in polymer crystal structures. Typical polymers that exhibit this trans form include polyethylene, poly(vinyl alcohol), syndiotactic forms of poly(vinyl chloride) and poly(l, 2-butadiene), most polyamides, and cellulose. Note that trans conformation is different from the trans configuration discussed in Section IV.A. 

Cationic cyclization of unsaturated elastomers such as poly(c -l,4-isoprene), poly(3,4-isoprene), poly(l,2-butadiene), and poly( 1,4-butadiene) usually leads to the formation of cyclized resinous products of no commercial value. An extensive review on the subject has been published by Schults et al. (1983). Cyclization of unsaturated elastomers, such as polyisoprene, can be carried... 

Butadiene, the simplest of the conjugated dienes, is produced commercially by thermal cracking of petroleum fractions and catalytic dehydrogenation of butane and butene. Polymerization of butadiene can potentially lead to three poly(l,2-butadiene)s, atactic, isotactic, and syndiotactic, and two cis and irons forms of poly(l,4-butadiene). This is discussed in Chapters 2 and 3. 

Block copolymers can also be hydrogenated to produce unique products. Hydrogenated triblock copolymers of poly(styrene-co-butadiene-co-styrene) (SBS) are commercially available from the Shell Company under the trade name Kraton G. The middle block is usually a mixed microstructure of poly(l, 2-butadiene) and poly (1,4-butadiene) units. The resulting product is a hydrogenated unsaturated polymer which exhibits greater thermal and oxidative properties than the parent SBS triblock. 

Conj ugated Ladder Polymers. Since the 1930s double-stranded, ladder-type polymers have been prepared in a multistep process with limited success of cyclization (191,192). Other routes have also been explored such as those for poly(acrylonitrile) (193,194), poly(l,2-butadiene), poly(3,4-isoprene) (195), or poly(butadiyne)s (196). These materials were found to be poorly soluble and unworkable, with a considerable number of defects in the structure (incomplete cyclization, cross-linking, radical sites). The first successful synthesis of a ladder polymer with a completely defined structure was accomplished in 1991 by Sherf and Mullen (197). The first step was the AA/BB-t5q)e polycondensation of an aromatic diboronic acid with a substituted 2,5-dibromo-l,4-dibenzoylbenzene to give a single-stranded precursor PPP-type polymer, followed by cyclization to the ladder structure (Fig. 8). Several other examples exist that have resulted in ladder-type structures. These include angular polyacene (198,199), Diels-Alder polyaddition of AB-type diene-dienophiles (200), AA/BB-type Diels-Alder polyaddition of a bisdiene and a bisdienophile (201), thienylene imits (202),... 

In addition to pore size, the mechanical strength of polymer substrates has an influence on the behaviour of cells, as cells sense their environment through the focal adhesions that attach the cytoskeleton to the scaffold.The mechanical properties of elastomeric poly(l,2-butadiene) (PB) honeycomb patterned films can be controlled by crosslinking the films under UV radiation.Crosslinking of the PB films resulted in a 15-fold increase in the elastic modulus but had no effect on the surface properties of the polymer. Murine fibroblasts exhibited stronger adhesions to the crosslinked PB films. When attached to a growth substrate, cells apply a traction force of 30 nN to the surface. Simulation of this force on the... 

Fiber glass laminates Poly(l,2-butadiene) Japan 149,285 1978 Fujitsu Ltd. 

Evaluation of IR spectra of acrylonitrile-butadiene-styrene (ABS) after UV irradiation shows that rubber double bands at 965 cm and 910 cm (Fig. 3.65), attributed to poly(trans-l,4-butadiene) and poly(l,2-butadiene), respectively, decrease with exposure time (Fig. 3.66) in a first order reaction, together with the carbon-carbon double stretching band at 3450 cm in addition, a saturated carbonyl band (centred at 1725 cm ) forms (Fig. 3.65) by a first order process (Fig. 3.67). During the initial stages of the photooxidation, bands at 1665, 1685 and 1699 cm due to a- and ) -unsaturated carbonyl groups, develop [1113,1936]. 

Kokkoli et al. [94] reported on the use of peptide-functionalized polymersomes composed of poly(l,2-butadiene)-b-poly(ethylene oxide) for siRNA delivery. 

Poly(l,2-butadiene) (>90% 1,2-structure) prep ired by reaction of butadiene with a complex of butyl lithium and tetramethylethylene diamine was a tacky substance [tjiOi <0.5) 23, 24). Treatment of this material in xylene at 120° with sulfuric acid as catalyst 5uelded a cream-colored powder (j inj, = 0.18), the infrared (IR) and nuclear magnetic resonance (NMR) spectra of which indicated that cyclization had occurred. Aromatization of the cydized material was attempted using chloranil as oxidant, XV -> XVI. 

He J, Wang J (2009) Preparation and characterization of epoxidate poly(l,2-butadiene) -toughened diglycidyl ether bisphenol-a epoxy composites. J Appl Polym Sci 113 3165-3170. doi 10.1002/app... 

Figure 5.30 Schematic illustration of a polyion complex (PIC) vesicle generated by blending a poly(l,2-butadiene-Z)-cesium methacrylate) block ionomer with an oppositely charged poly(styrene-Z)-l-methyl-4-vinylpyridinium iodide) block ionomer. Note that the internal and external polymer brushes are chemically dissimilar, demonstrating the fine tunability and enhanced versatility of this class of materials. (Adapted from Schrage, S., Sigel, R. and Schlaad, H. Macromolecules 36, 1417, 2003, and reprinted with permission. Copyright (2003) American Chemical Society.)...

Poly(l,2-butadiene)-btoc< -poly(styrene) Chromatography Tetrahydrofuran SEC, phenogel, 25°C 1022... 

---