Hydrogenated block copolymers isoprene

Commercially, anionic polymerization is limited to three monomers styrene, butadiene, and isoprene [78-79-5], therefore only two useful A—B—A block copolymers, S—B—S and S—I—S, can be produced direcdy. In both cases, the elastomer segments contain double bonds which are reactive and limit the stabhity of the product. To improve stabhity, the polybutadiene mid-segment can be polymerized as a random mixture of two stmctural forms, the 1,4 and 1,2 isomers, by addition of an inert polar material to the polymerization solvent ethers and amines have been suggested for this purpose (46). Upon hydrogenation, these isomers give a copolymer of ethylene and butylene. 

Hydrogenated Linear Block Copolymers of Butadiene and Isoprene... 

Significant modification in properties of polymers and block copolymers containing isoprene and/or butadiene have been reported following hydrogenation of these macromolecules.(9,13-18)... 

Polymer Synthesis and Characterization. This topic has been extensively discussed in preceeding papers.(2,23,24) However, we will briefly outline the preparative route. The block copolymers were synthesized via the sequential addition method. "Living" anionic polymerization of butadiene, followed by isoprene and more butadiene, was conducted using sec-butyl lithium as the initiator in hydrocarbon solvents under high vacuum. Under these conditions, the mode of addition of butadiene is predominantly 1,4, with between 5-8 mole percent of 1,2 structure.(18) Exhaustive hydrogenation of polymers were carried out in the presence of p-toluenesulfonylhydrazide (19,25) in refluxing xylene. The relative block composition of the polymers were determined via NMR. 

The hydrogenated (H) block copolymers will be designated by giving the butadiene (B) or isoprene (i) block sequence followed by a number which represents the total weight percentage of butadiene in the polymer. For example HBIB-27 is a hydrogenated triblock copolymer of butadiene-isoprene-butadiene which contains 27% butadiene. Since the polymer is symmetric, the relative composition of each block is therefore 13.5% B -73% I -13.5% B. 

The use of olefin rubbers [18] as good impact modifiers for sPS when used in conjunction with S-B or S-B-S block copolymers, which may be hydrogenated in the butadiene phase, has also been described. Instead of butadiene, isoprene can be used. Examples of the olefinic polymers are polyethylene, ethylene-propylene rubbers (EPR) and polypropylene-(ethylene propylene rubber) block copolymers. Here the styrene block copolymers presumably function as... 

In 1961, using lithium catalyst, a series of sty-rene-isoprene (SI) and styrene-butadiene (SB) block copolymers were synthesized [Bull and Holden, 1977]. The resins had T = -90 to -i-90°C. Full-scale production started in 1965. Since then, numerous two- and three- block copolymers have been developed. More recently, hydrogenated and during the last few years maleated block copolymers are being offered. With the world consumption of 330 kton/y, the block copolymers constitute the largest part of the commercial TPE market. Large quantity of SBS resin is used... 

PPE, PP and PPS with hydrogenated styrene-isoprene block copolymers heat, impact and solvent resistance Maruyama Mizuno, 1990... 

One of the major areas for potential involves the synthesis of polyolefin block copolymers. A PP-EPR-PP or PE-EPR-PE block copolymer could have large potential as is or in blends with other polyolefins. PE-EPR-PE block copolymers have been synthesized via anionic polymerization of butadiene-isoprene-butadiene ABA block copolymers followed by hydrogenation [Mohajer et al, 1982 Rangarajanout et al., 1993]. These materials would have utility in hot melt adhesive formulations as well as general-purpose thermoplastic elastomer applications. Improvements on the synthesis procedures to offer viable approaches to polyolefin block copolymers could open up a new class of commercial polyolefins. In summary, several opportunities exist for new combinations of commercial blends from the list of commodity polymers. 

Orientations in elongated mbbers are sometimes regular to the extent that there is local crystallization of individual chain segments (e.g., in natural rubber). X-ray diffraction patterns of such samples are very similar to those obtained from stretched fibers. The following synthetic polymers are of technical relevance as mbbers poly(acrylic ester)s, polybutadienes, polyisoprenes, polychloroprenes, butadiene/styrene copolymers, styrene/butadiene/styrene tri-block-copolymers (also hydrogenated), butadiene/acrylonitrile copolymers (also hydrogenated), ethylene/propylene co- and terpolymers (with non-conjugated dienes (e.g., ethylidene norbomene)), ethylene/vinyl acetate copolymers, ethyl-ene/methacrylic acid copolymers (ionomers), polyisobutylene (and copolymers with isoprene), chlorinated polyethylenes, chlorosulfonated polyethylenes, polyurethanes, silicones, poly(fluoro alkylene)s, poly(alkylene sulfide)s. 

Elastomeric styrene containing compounds, such as styrene-buta-diene-styrene block copol mriers, or styrene-isoprene-styrene block copolymers, including its hydrogenated homologues, all of them containing vegetal or even mineral oils in their formulations, can be made biodegradable (13). This is achieved by the admixture of brewer s yeast or yeast mother in amounts of 1-4%. 

Studies of polymers dissolved in various oils indicate general agreement, with the volume fraction exponent reported to be 2 to 2.3 (5,6). In a recent study, W.W. Graessley and co-workers (7) reported exponents of 2.22 and 2.26 for polybutadiene and hydrogenated polybutadiene in various diluents. G. Kraus and K.W. Rollmann (8) reported on the only study of resins as the polymer diluent. Using a styrene-isoprene-styrene block copolymer, they found exponents of 2.28 for the glycerin ester of stabilized rosin and 2.62 for a C -stream resin. Plateau modulus was identified as G in the rubbery plateau where tan 6 was a minimum in a temperature scan of the systems. 

P(HB-b-I-S) Block copolymer of hydrogenated butadiene, isoprene, and styrene P(S-b-MMA) Block copolymer of styrene and methyl methacrylate PA Polyamide... 

PP was blended with hydrogenated styrene-butadiene or styrene-isoprene block copolymer, 6-8 wt%. The alloys were used for the manufacturing of materials with good transparency and impact strength... 

Polymer modified asphalt originated in Europe in the early 1960s. Atactic PP is still used today in asphalt compositions mainly in Europe, Mexico and Asia. A PP copolymer containing 2-10% ethylene is more popular in USA. Thermoplastic block copolymers with styrene end blocks or with a diene midblock like S-B-S and styrene-isoprene-styrene (SIS) and their hydrogenated versions are common modifiers for asphalt [40]. 

---