STYRENE-BUTYL COPOLYMER

Of the amorphous block copolymers, styrenic block copolymers are the vast majority. These are synthesized anionically in solution, with butyl lithium commonly employed as the initiator [4]. There are three processes for this polymerization ... 

Currently, important TPE s include blends of semicrystalline thermoplastic polyolefins such as propylene copolymers, with ethylene-propylene terepolymer elastomer. Block copolymers of styrene with other monomers such as butadiene, isoprene, and ethylene or ethylene/propy-lene are the most widely used TPE s. Styrene-butadiene-styrene (SBS) accounted for 70% of global styrene block copolymers (SBC). Currently, global capacity of SBC is approximately 1.1 million tons. Polyurethane thermoplastic elastomers are relatively more expensive then other TPE s. However, they are noted for their flexibility, strength, toughness, and abrasion and chemical resistance. Blends of polyvinyl chloride with elastomers such as butyl are widely used in Japan. ... 

As an illustration we refer to the data of Lackdavala and Salovey [160] who studied the flow of styrene/butyl methacrylate copolymer composites with ash of... 

A prime example of these features can be found in the synthesis of styrene/ (meth)acrylate random copolymers. By controlling the initiator/total monomer ratio, the molecular weight can be accurately controlled for both styrene/methyl methacrylate and styrene/butyl acrylate random copolymers. As can be seen in Figure 2.3 the polydispersity for both systems is essentially 1.10-1.25 over comonomer ratios ranging from 1/9 to 9/1. 

Buna-S Elastomeric copolymer of butadiene and styrene, butyl rubber Elastomeric copolymer of isobutylene and isoprene. 

Over 5.5 billion pounds of synthetic rubber is produced annually in the United States. The principle elastomer is the copolymer of butadiene (75%) and styrene (25) (SBR) produced at an annual rate of over 1 million tons by the emulsion polymerization of butadiene and styrene. The copolymer of butadiene and acrylonitrile (Buna-H, NBR) is also produced by the emulsion process at an annual rate of about 200 million pounds. Likewise, neoprene is produced by the emulsion polymerization of chloroprene at an annual rate of over 125,000 t. Butyl rubber is produced by the low-temperature cationic copolymerization of isobutylene (90%) and isoprene (10%) at an annual rate of about 150,000 t. Polybutadiene, polyisoprene, and EPDM are produced by the anionic polymerization of about 600,000, 100,000, and 350,000 t, respectively. Many other elastomers are also produced. 

Styrene monomer and a styrene/butadiene copolymer are fed to the first reaction zone. The polymerization is initiated either thermally or chemically. Many chemical initiators are available such as ferf-butyl peroxybenzoate and ferf-butyl peracetate. Conditions are established to prevent a phase inversion or the formation of discrete rubber particles in the first reaction zone. The conversion in the first reaction zone should be 5-12%. An important function of the first reaction zone is to provide an opportunity for grafting of the styrene monomer to the elastomer (8). 

ASA structural latexes have been synthesized in a two stage seeded emulsion polymerization. In the first stage, partially crosslinked poly(n-butyl acrylate) and poly( -butyl acrylate-sfaf-2-ethylhexyl acrylate) rubber cores are synthesized. In the second stage, a hard styrene acrylonitrile copolymer (SAN) shell is grafted onto the rubber seeds (16). 

J.A. Herbig and 1.0. Salyer, Binary blends of styrene/acrylonitrile copolymer and butyl acrylate/acry-lonitrile copolymer and methods for preparing the same, US Patent 3118855, assigned to Monsanto Chemicals, January 21,1964. 

Handel and co-workers [11] have investigated the influence of the polymerization conditions on the molecular weight and chemical composition of styrene-butyl acrylate copolymers ... 

Figure 7.1.9 Contour plot obtained for a typical GPC-NMR on-line coupling analysis of a styrene-butyl acrylate copolymer...

The cationic Surfmers produced much smaller particle sizes in the emulsion polymerization of styrene and styrene/butyl acrylate than the amphoterics (20-50 nm versus 100-300 nm). Some of the latter, however, conferred to the copolymer lattices stability to electrolytes and freeze-thaw [24]. Similar, but nonreactive surfactants produced from succinic anhydride gave similar stability but had much inferior water resistance [25]. 

Polymeric supports can also be used with advantage to form monofunctional moieties from difunctional (Hies. Leznoff has used this principal in the synthesis of sex attractants on polymer supports (67). Starting from a sheap symmetrical diol he blocked one hydroxyl group by the polymer. Functionalization of cross-linked polymers is mostly performed by chloromethylation (65). A very promising method to introduce functional groups into crosslinked styrene-divinylbenzene copolymers is the direct lithiation with butyllithium in presence of N,N,N, N -tetramethyl-ethylenediamine (TMEDA) (69, 70). Metalation of linear polystyrene with butyl-lithium/TMEDA showed no exchange of benzylic hydrogen and a ratio of attack at m/p-position of 2 1 (71). In the model reaction of cumene with amylsodium, a kinetic control of the reaction path is established. After 3h of treatment with amyl-sodiuni, cumene is metalated 42% in a-, 39% m-, and 19% p-position. After 20h the mixture equilibrates to affort 100% of the thermodynamically more stable a-prod-uct (72). 

Watanabe62) studied systematically the copolymerization of ra-methacryloyl-polyoxyethylenes, with monomers such as acrylonitrile, styrene, butyl methacrylate, and methacrylic acid. It should be mentioned that the macromonomers that he prepared are very short so that no difficulties were encountered to isolate the graft copolymers formed. There are many applications for these graft copolymers, e.g. as additives in polyacrylonitrile films and fibers they cause improved antistatic properties. They have been tested as varnishes, coatings, and wood dimensional stabilization agents. 

Inaba et al. prepared a series of model styrene/butyl acrylate copolymer latexes with glass transition temperatures at room temperature. The functional monomer 2-(3-isopropenylphenyl)-2-methylethylisocyanate (TMI) was used as monomer/crosslinking agent for further film formation. A small amount of methacrylic acid was introduced in some formulations in order to enhance the crosslinking reaction. A redox initiation system was used to reduce premature crosslinking during the polymerization [82]. 

DiPaola-Baranyi, G., "Thermodynamic Miscibility of Various Solutes with Styrene-Butyl Methacrylate Polymers and Copolymers," Macromolecules, 14, 683 (1981). 

Addition of the XIII as a macroinitiator to styrene polymerization resulted in the formation of S-MMA-S triblock copolymer. The same procedure was also used to make styrene-butyl acrylate block copolymers. 

Monofunctional Initiators. AB, ABA, and multiblock copolymers can be synthesized by initiation of one monomer with a monofunctional initiator like n-butyl lithium. When the first monomer has been reacted, a second monomer can be added and polymerized. This monomer addition sequence can be reversed and repealed if the anion of each monomer sequence can initiate polymerization of the other monomer. The length of each block is determined by the amount of the corresponding monomer which was provided. Styrene-isoprene-styrene block copolymers can be made by this method by polymerizing in benzene solution and adding the styrene first. Addition of a small amount of ether accelerates the slow attack of dienyl lithium on styrene. 

As a general statement, isomerizations occur much slower (around lOOtimes and more) in the film than in solution. It was already observed for azo compounds by Kamogawa et in the case of copolymers of 4-vinyl-4 -dimethylaminoazobenzene (I) with styrene and of 4-acryloylaminomethylaminoazobenzene (II) with styrene, butyl acrylate and methyl methacrylate. 

NOTE Ibtals for plastics are for those products listed and exclude some small-volume plastics. Synthetic rubber data include Canada. Dry-weight basis unless otherwise specified Density 0.940 and below " Data include Canada from 2001 Density above 0.940 Data include Canada from 1995 Data include Canada from 2000 Data include Canada from 1994 Includes styrene-butadiene copolymers and othm styrene-based polymers Unmodified Includes butyl styrene-butadiene rubber latex, nitrile latex, polyisoprene, and miscellaneous others. SOURCES American Plastics Council, International Institute of Synthetic Rubber Producers. 

The above mentioned polymer-supported oxazaborolidines are prepared from polymeric amino alcohols and borane. Another preparation of polymer-supported oxazaborolidines is based on the reaction of polymeric boronic acid with chiral amino alcohol. This type of polymer can be prepared only by chemical modification. Lithiation of the polymeric bromide then successive treatment with trimethyl borate and hydrochloric acid furnished polymer beads containing arylboronic acid residues 31. Treatment of this polymer with (li ,2S)-(-)-norephedrine and removal of the water produced gave the polymer-supported oxazaborolidine 32 (Eq. 14) [41 3]. If a,a-diphenyl-2-pyrrolidinemetha-nol was used instead of norephedrine the oxazaborolidine polymer 33 was obtained. The 2-vinylthiophene-styrene-divinylbenzene copolymer, 34, has been used as an alternative to the polystyrene support, because the thiophene moiety is easily lithiated with n-butyl-lithium and can be further functionalized. The oxazaborolidinone polymer 37 was then obtained as shown in Sch. 2. Enantioselectivities obtained by use of these polymeric oxazaborolidines were similar to those obtained by use of the low-molecular-weight counterpart in solution. For instance, acetophenone was reduced enantioselectively to 1-phe-nylethanol with 98 % ee in the presence of 0.6 equiv. polymer 33. Partial elimination of... 

Plots of the relationship between the styrene content and retention volume for copolymers of styrene-acrylate and styrene-methacrylate with the same ester group lay roughly on the same line. This result indicates that a pair of copolymers with the same ester group and the same styrene content could not be separated (24), For example, copolymers of styrene-methyl acrylate and styrene-MMA with the same styrene content cannot be separated by this technique. In copolymers with the same styrene content, styrene-butyl acrylate and styrene-butyl methacrylate copolymers eluted first from a column, the copolymers of ethyl esters were next, and those of methyl esters eluted last. 

Significant developments in synthetic rubber began at this time. Outstanding were the introduction of polychloroprene (neoprene) by Carothers, and of the oil-resistant polysulfide rubber Thiokol by Patrick. These were soon followed by styrene-butadiene copolymers, nitrile rubber, butyl rubber, and various other types, some of which were rushed into production for the war effort in the early 1940s. The stereospecific catalysts researched by Ziegler and Natta aided this development, including synthesis of true rubber hydrocarbon (polyisoprene). Since 1935 synthetic rubbers have been referred to as elastomers. 

The JG and the a-Relaxations of Poly(n-butyl methacrylate) in Poly(n-butyl-methacrylate-stat-styrene) Random Copolymers. The copolymers of poly(n-butyl methacrylate) (PwBMA) and polystyrene (PS) is one example [338,339]. Here PnBMA is the lower Tg component A. Neat PnBMA has n = 0.47 and a JG relaxation. On increasing the styrene content from 0 to 66 mol% in the copolymer, a monotonic increase of nA of the PnBMA component leads to a concomitant increase in the separation of the JG relaxation from the segmental relaxation, both of the PwBMA component. This changes were observed in the dielectric relaxation experiment. 

---