Polymers from Dienes

There are many reports in the literature of preparations of polymers from various other substituted dienes. Most have no commercial significance. Some are, however, interesting materials. An example is a polymer of 2-r-butyl- 1,3-butadiene formed with TiCU and either alkylaluminum or aluminum hydride catalysts.The polymer is crystalline and melts at 106 C. It can be dissolved in common solvents. Based on X-ray data, the monomer placement is high ci5-l,4. 

Poly(carboxybutadiene)s also form with coordination catalysts 

X-ray crystallography showed that the placement is rrons-isotactic. Based on the mode of packing of the chains in the crystalline regions and from the encumbrance of the side groups in relationship to the main chain, an erythro configuration can be assigned.The polymers are therefore trans-erythro-vsoXSiCixc, 

Polymerization of 1,3-pentadiene can potentially result in five different insertions of the monomers. These are 1,4-cw,, A-trans, 1,2-ds,, 2-trans, and 3,4. In addition, there are potentially 3-cw-l,4 and 2 -trans- A structures (isotactic, syndiotactic, and atactic). Formations of trans-, A-isotactic, c/s-1,4-isotactic, and cw-l,4-syndiotactic polymers are possible with Ziegler-Natta cata-lysts. Amorphous polymers also form that are predominantly cw-l,4 or rra/w-1,4, but lack tactic order. Stereospecificity in poly( 1,3-pentadiene) is strongly dependent upon the solvent used 

---

Isomeric polymers can also be obtained from a single monomer if there is more than one polymerization route. The head-to-head placement that can occur in the polymerization of a vinyl monomer is isomeric with the normal head-to-tail placement (see structures III and IV in Sec. 3-2a). Isomerization during carbocation polymerization is another instance whereby isomeric structures can be formed (Sec. 5-2b). Monomers with two polymerizable groups can yield isomeric polymers if one or the other of the two alternate polymerization routes is favored. Examples of this type of isomerism are the 1,2- and 1,4-polymers from 1,3-dienes (Secs. 3-14f and 8-10), the separate polymerizations of the alkene and carbonyl double bonds in ketene and acrolein (Sec. 5-7a), and the synthesis of linear or cyclized polymers from non-conjugated dienes (Sec. 6-6b). The different examples of constitutional isomerism are important to note from the practical viewpoint, since the isomeric polymers usually differ considerably in their properties. 

Enormous commerical applications flowed from the revolution initiated by Ziegler and Natta. These include high-density and linear low-density polyethylenes (HDPE, LLDE), polypropene, ethene-propene co- and terpolymers, and polymers from 1,3-dienes (Sec. 8-10). The annual United States production of these polymers exceeded 40 billion pounds in 2000 the global production was about 3-3.5 times the U.S. production. Ziegler-Natta chemistry accounts for the production of one-third of all polymers. 

Ziegler-Natta catalysts can also be used for preparation of stereoregular polymers from 1,3-dienes. For example, polyisoprene with 96-97 per cent cw-1,4 content (i.e. synthetic natural rubber ) can be prepared using catalysts obtained from TiCU-f Ai Bu3. 

STRUCTURE AND ARRANGEMENT OF UNITS IN POLYMERS FROM DIENES... 

B16. Butler, G. B., and A. Crawshaw The formation of linear polymers from diene monomers by a cyclic polymerisation mechanism. II. Polyacrylic anhydride and the derived polyacrylic acid. J. Am. Chem. Soc. 80, 5464 (1958). 

Introduction to polymers Cationic polymerization Conducting organic polymers Radical polymerization Polymers from dienes Polyesters and polyamides Polysaccharides N-Glycosides (DNA and RNA)... 

Polyethylene possesses several outstanding properties. It is an excellent electrical insulator with a very high volume resistivity and a very low power factor, the latter virtually independent of temperature and current frequency it has the excellent chemical resistance typical of an alkane and although it may be oxidized it is much better in this respect than the polymers from diene hydrocarbons there are no solvents at normal ambient temperatures although some liquids facilitate stress-cracking and, by no means least, it is made from a low cost monomer and is amongst the least expensive of synthetic polymers. 

Synthetic Rubbers. Synthetic rubbers are polymers with rubberlike characteristics that are prepared from dienes or olefins. Rubbers with special properties can also be prepared from other polymers, such as polyacrylates, fiuorinated hydrocarbons, and polyurethanes. 

Chemistry on solid support has gained tremendous importance during the last few years, mainly driven by the needs of the pharmaceutical sciences. Due to the robust and tolerable nature of the available catalysts, metathesis was soon recognized as a useful technique in this context. Three conceptually different, RCM-based strategies are outlined in Fig. 11. In the approach delineated in Fig. 1 la, a polymer-bound diene 353 is subjected to RCM. The desired product 354 is formed with concomitant traceless release from the resin. This strategy is very favorable, since only compounds with the correct functionality will be liberated, while unwanted by-products remain attached to the polymer. However, as the catalyst is captured in this process by the matrix (355), a higher catalyst loading will be required, or ancillary alkenes have to be added to liberate the catalyst. 

Functionalized copolymers from dienes and p-alkylstyrenes can serve as dispersants and viscosity index improvers. The functionalities are introduced via the aromatic units [233,234]. The polymers are selectively hydrogenated to produce polymers that have highly controlled amounts of unsaturation, permitting a highly selective functionalization. The dispersant substances may also include a carrier fluid to provide concentrates of the dispersant. 

To explain the formation of non-crosslinked polymers from the diallyl quaternary ammonium system, Butler and Angelo proposed a chain growth mechanism which involved a series of intra- and inter-molecular propagation steps (15). This type of polymerization was subsequently shown to occur in a wide variety of symmetrical diene systems which cyclize to form five or six-membered ring structures. This mode of propagation of a non-conjugated diene with subsequent ring formation was later called cyclopolymerization. 

The first approach involves RCM of a polymer bound diene 77 and results in the formation of a cyclic product 78 which remains attached to the polymer support. This product can undergo further manipulation, with cleavage from the resin occurring at a later stage. In a second, complementary approach, RCM proceeds with concomitant cleavage of the substrate from the resin (80 81). The latter protocol is highly attractive since only compounds possessing the correct... 

In the case of earbon-chain polymers such as vinyl polymers or diene polymers, the generic name is to be used only when different polymer structures may arise from a given monomeric system. 

Mechanisms have been proposed to explain stereoselectivity in 1,3-diene polymerizations, but these processes are less understood than the polymerization of ethylene and 1-alkenes [Peluso et al., 1997]. The ability to obtain cis 1,4-, trans 1,4-, and st 1,2-polymers from 1,3-butadiene, each in very high stereoregularity, hy using different initiators has great practical utility for polymer synthesis even if it is not well understood why a particular initiator gives a particular stereoregular polymer. 

The importance of coordination polymerization of alkenes and dienes is evident when it is noted that more than 40 billion pounds of polymers were produced by this route in the United States in 2001. This corresponds to 35 10% of the total industrial production of polymers from monomers containing carbon-carbon double bonds. 

The photo-cross-linkability of a polymer depends not only on its chemical structure, but also on its molecular weight and the ordering of the polymer segments. Vinyl polymers, such as PE, PP, polystyrene, polyacrylates, and PVC, predominantly cross-link, whereas vinylidene polymers (polyisobutylene, poly-2-methylstyrene, polymethacrylates, and poly vinylidene chloride) tend to degrade. Likewise, polymers formed from diene monomers and linear condensation products, such as polyesters and polyamides, cross-link easily, whereas cellulose and cellulose derivatives degrade easily. ... 

Anionic polymerizations initiated with alkyllithium compounds enable us to prepare homopolymers as well as copolymers from diene and vinylaromatic monomers. These polymerization systems are unique in that they have precise control over such polymer properties as composition, microstructure, molecular weight, molecular weight distribution, choice of functional end groups and even copolymer monomer sequence distribution. Attempts have been made in this paper to survey these salient features with respect to their chemistry and commercial applications. 

The use of benzocyclobutene as the source of the diene in a Diels-Alder polymerization offers a unique solution to the problems described above. Benzocyclobutene containing monomers can be stored indefinitely at room temperature without concern for further advancement of the molecular weight. It is only when benzocyclobutene is heated to temperatures of approximately 200 °C that the reactive diene, o-quinodimethane, is formed at a significant rate and enters into reaction with the dienophile. The only requirement of the dienophile is that it must be stable at these temperatures and not undergo reaction with itself. The most common dienophiles that have been successfully used in the formation of polymers from AB type benzocyclobutene monomers have been acetylenes, olefins and maleimides. 

The most important feature of ionizing radiations is, as the term implies, ionization to give ionic intermediates in irradiated systems. Though radiation-induced radical polymerization had long been studied, it is only a decade since radiation-induced ionic polymerization was first found. In 1957, Davison et al. obtained polymer from isobutene, which is known not to be polymerized by radical catalysts, by irradiating at low temperature with y-rays (7). Before long, the radiation-induced polymerization of styrene was proved to proceed as an ionic mechanism in suitable solvents (2,3,4). Since these pioneering researches, the study of the chemical kinetics of radiation-induced ionic polymerization has been extended to several vinyl, diene and cyclic monomers. 

Linear polymers from conjugated dienes readily undergo oxidation in air, in some cases even at room temperature (14). The allylic carbon... 

Unsaturated polymers derived from dienes have also been hydrofor-mylated 102,113,122). 

---