MXPA99011139A - Block copolymers of styrene-butadi - Google Patents

Abstract

This invention is based on the unexpected discovery that styrene-butadiene block copolymers, having blocks of syndiotactic polystyrene (sPS) and blocks of cis-1,4-polybutadiene, can be synthesized by the polymerization of styrene and 1, 3-butadiene using certain catalyst systems, when the polymerization is carried out at an approximate pressure within the range of 10 to 50 hg ion and at an approximate temperature within the range of 0 to 100 ° C. The invention specifically describes a styrene-butadiene block copolymer, comprising (a) syndiotactic polystyrene blocks and (b) cis-1,4-polybutadiene blocks, in which these blocks of cis-1,4-polybutadiene have a vinyl content of up to 20 percent, and the syndiotactic polystyrene blocks have a syndiotactic microstructure content of at least 50 percent, where the block copolymer contains at least 5 blocks of syndiotactic polystyrene and the block copolymer has an average molecular weight in number within the approximate range of 10,000 to 700.0

Description

STYRENE-BUTADIENE BLOCK COPOUMMERS BACKGROUND OF THE INVENTION The term "metallocene" was first used in the mid-1950s as a replacement for the familiar expression of "iron sandwich", a given name of the CpFe, where Cp is cyclopentadienyl, after the binding mode? 5 of the Cps were first independently described by Wiikinson and Fischer in 1954. Now, the term is used to describe any transition metal complex having one or more Cp or substituted Cp ligatures attached to it (see KB Sinclair and RB Wileon, Chem Ind 1994, 7, 857). Much of the initial interest and research in the area of the anterior metallocenes curved in a metal (a metallocene with two Cps, where the angle of Cp (centroid) - metal - Cp (centroid) is less than 1802, example CpTiCl2) should be to an effort to model the highly active and heterogeneous stereoselective polymerization catalysts Ziegler-Natta (see HH Brintzinger et al, Angew Chem Int Ed Engl 1995, 34, 1143), which are based on the above metals, such as TiCln / AlRm-pClp, where R is an alkyl group, for example methyl (Me) or ethyl (Et), n is 3 or 4, m is 3 and p is 1 6 2 (see P Locatelli et al., Trends Poly Science 1994, 2, 87).

The curved metallocene models, based particularly on the Group IV metals, offered the hope of finding out the key characteristics of the homogeneous polymerizations that they catalyze. It is believed that this information may be related to the field of conventional Ziegler-Natta catalysts. As models, the curved metallocenes of Group IV metals offer several advantages. These advantages include a simple coordination geometry, only two reactive binding sites with cis orientation, and from a practical point of view, the compatibility with spectroscopic techniques, such as Magnetic Resonance-Nuclear (NMR), allowing the most direct observation of the active catalyst species. It would now seem that these "models" are replacing the existing Ziegler-Natta polymerization catalyst systems in many applications (see H H Brintzinger et al, Angew Chem Int Ed Engl 1995, 34, 1143). It has been known since the mid-1950s that Cp2TiCl2 and Et2AlCl catalyze the formation of polyethylene under conditions similar to those used in conventional Ziegler-Natta heterogeneous catalysts (see DS Breslow and NR Newburg, J Am Chem Soc 1957, 79, 5072). By 1960, several of the key features in systems like these have been deduced by several spectroscopic techniques. Key features include the formation of Cp2TiRCl, where R is Me, Et or a related species, by exchange with the alkylaluminum co-catalyst, the Ti-Cl bond polymerization in this species by Lewis acid centers, which form an adduct of the type CpTiRCl? lRCl2, and the insertion of the olefin in the Ti-R bond of these electron-deficient species. However, these types of model systems are only able to polymerize ethylene, which is in contrast to heterogeneous Ziegler-Natta catalysts, which can also polymerize propylene. This limitation proved to be a serious obstacle to progress in this field. Penetration occurred in the late 1970s, when Sinn and Ka insky casually observed that the addition of small amounts of H20 to the otherwise inactive catalyst system of CpMMe2 / AlMe3, where M is Ti or Zr, imparted a surprisingly high activity for the polymerization of ethylene (see H Sinn and W Kaminsky, Adv Organomet Chem 1980, 18, 99). It is suspected that partial hydrolysis of Al Mß3 formed methylaluminoxane (MAO), which has the general formula Me2A10- [Al (Me) 0] n-AlMe2, where n represents generally an integer from 5 to 20, which acts as a efficient co-catalyst. This idea was supported by directly synthesizing the MAO and successfully using it as a co-catalyst with not only the Cp2ZrM2, but also Cp2ZrCl2 (see Sinn et al, Angew Chem Int Ed Engl 1980, 19, 296). The activity in certain examples is even greater than in conventional Ziegler-Natta catalyst systems. Activity as high as 40,000 kg PE / g metal / h has been reported using zirconocene catalysts, activated with MAO with an Al: Zr ratio of 12,000 (molecular weight = 78,000) (see W Kaminsky et al., Makromol Chem Rapid Commun 1983, 4, 417). Likewise, Sinn and Kaminsky demonstrated that these types of homogenous metallocene catalysts activated with MAO are capable of polymerizing propylene and other α-olefins, however, without any stereoregularity (see H Sinn and W Kaminsky, Adv Organo et Chem 1980, 19 , 99). The role of MAO in the metal metallocene catalysts above is now believed to be triple. First, MAO acts as an alkylating agent for the generation of metal-alkyl adducts. Second the MAO acts as a strong Lewis acid, extracting an anionic bond, whereby a crucial alkyl cationic species is formed. Finally, the MAO and especially the impurities of AlMß3 in the MAO act as a scavenger to remove the catalyst poisons (for example, the H20 that would react with the AlMßß, forming more MAO) in the olefin and the solvent (see AD Horton, Trends Polym Sci 1994, 2, 158).

The role of the MAO as a co-catalyst is now well understood enough; however, at the time of Kaminsky and Sinn's discovery this was not the case. The nature of the active catalyst species, derived from these anterior metallocene model complexes, activated with MAO, remains unclear. The nature of this problem is the remarkably complex nature of MAO, as well as the large excess required for high activity. In fact, the exact structure (s) of the MAO remain unknown until now (see J C W Chien et al., J. Poly Sci, Part A, Poly Chem 1991, 29 (4), 459). Much of the debate at that time was about whether or not the active species were bimetallic or cationic. Natta, Sinn and others supported the theory that suggests that the active catalyst is a bimetallic species in which the alkyl or halide group forms a bridge with the Group IV metal and the aluminum center promotes the insertion of the olefin (see G Natta et al. G Mazzanti, Tetrahedron 1969, 8, 86). Shilov and others supported the theory that suggests that olefin insertion actually occurs in a true cationic species, such as [Cp2TiR] + (see A K Zefirova and A E Shilov, Dokl Akad Nauk SSSR 1961, 1362, 599). In 1986, Jordan helped solve this problem by isolating the tetraphenyl borate salts of zirconocene alkyl cations stabilized with a base, such as [Cp2ZrR (THF)] +, where R represents a group of Me or benzyl (Bz), and THF is tetrahydrofuran (see RF Jordan et al., J. Am Chem Soc 1986, 108, 1718). Jordan also demonstrated its ability to polymerize olefins without the presence of any co-catalyst (see R F Jordan, Adv Organomet Chem 1991, 32, 325). Subsequent research by Jordan and other groups supported the idea that an alkyl cation is a crucial intermediate product in polymerizations of metallocene-based olefins curved in a Group IV metal. Several requirements are now considered broadly critical in the formation of metallocene catalysts curved in a Group IV metal, active for the polymerization of the olefin. An active catalyst must have a dd, 14e ~, Lewis acid metal center, a coordinated unsaturated metal center, and a vacant cis coordination site to a reactive M-R bond. The metallocenes curved in a Group IV metal activated with large excesses of MAO can polymerize the α-olefins, but the large excess of the required MAO is often impractical from the industrial point of view, due to the high cost of the MAO, as that the requirement of the high catalyst residue left in the resulting polymer. A solution to this problem stems from the observation that the insertion of an olefin into an M-R bond can only occur if the counterion binds very weakly, noting that even large, bulky counterions, for example BPh / j ~ and CB9H? ~, coordinate the centers of the cationic metal, very strongly, producing catalysts with only moderate activity (see G G Hlatsky et al, J Am Chem Soc 1989, 111, 2728). In order to produce counterions that are weakly coordinated or not coordinated, the general idea of placing electron withdrawing substituents in the periphery of the center of the boron counterion has worked well. The most successful electron withdrawing substituents have been the fluorinated phenyls that produce stable, even weakly coordinated counterions (eg, B (C6F5) 3, [HNMe2Ph] [B (C6F5) 4] and [C (Ph) 3] [ B (CeF5)]). The resulting catalytic species are not only highly active polymerization catalysts, capable of polymerizing propylene and higher α-olefins, but have also demonstrated that active catalysts can be produced without base stabilization and without using MAO. You know that metal curved metallocene anterior catalysts have been developed based on Cp ligation, which are active for the polymerization of propylene, but none has been stereoselective. The ansa-metallocenes of chiral Group IV were developed by Brintziner using indenyl and tetrahydroindenyl ligatures bridging ethylene in the Group IV metal halides. These types of compounds are independently shown by Ewen, Kaminsky and Brintzinger, to maintain their chiral geometry in solution under catalytic conditions, which make possible the formation of highly isotactic poly-α-olefins, including isotactic polypropylene (see JA Ewen, J Am Chem Soc 1984, 106, 6355). These findings led to an extensive exploration of the mechanisms by which these catalysts control the stereochemistry of polymer growth. A large number of chiral metallocenes were synthesized in an attempt to understand how the binding geometry affects the catalyst activity, as well as the polymer microstructure, molecular weight and which olefins can be polymerized. It was soon discovered that greater catalytic activity can be achieved if the ethylene bridge is replaced with a silylene bridge unit. This produced a stiffer ligature framework, as well as favorable electronic characteristics (a dimethylsilane bridge is generally considered to donate electron density to the center of the metal) (see European Patent Application No. 302,424). It was also found that by placing the methyl groups in the 2 and 2 'positions of the indenyl bonds with bridges, the molecular weight of the polymer increases and the catalytic activity increases, again making a more rigid ligature system (as shown below) . Other advances in this area are related to the development of the co-catalyst and the idea of "pre-activating" a catalyst, by exposure to the MAO before introducing the monomer. In general, these improvements, while impressive, are still not appropriate in supplying a commercially viable catalyst. The area of the polymerization of ethylene, propylene and larger α-olefins, to form several thermoplastics, has been the most intense research area and the industrial application with respect to the metallocene catalysts. Catalysts with potential commercial viability for the formation of polypropylene (isotactic, syndiotactic and semi-isotactic) are described in the literature. These catalysts represent the state of the art in the area of polymerization of olefins, and demonstrate that it is possible and illustrate some of the nuances associated with the successful design of catalysts (see W Spaleck et al, Organometallics 1994, 13, 954). Spaleck extended the usefulness of the catalysts based on the indenyl bonds with dimethylsilylene bridges, systematically replacing different aromatic groups at positions 4, 4 * and 5, 5 'of the benzo-indenyl ring. This "rational catalyst design" approach allowed Spaleck to determine the best catalyst contained in a ligature that carries a portion of naphthyl at positions 4, 4 '(as shown below). The zirconium catalysts employing this ligation system showed remarkable polymerization characteristics, including high activity, high molecular weight of the polymer and excellent stereoregularity.

The extremely high activity of the Spaleck catalyst is impressive. However, solution polymerizations, in general, have certain intrinsic disadvantages, including high Al loads: Zr co-catalyst (eg 15,000: 1), lack of morphology control and reactor clogging.

The practical realization of metallocene catalysts, despite their high cost, comes from a number of important factors. The most important factor has been the ability to withstand metallocenes on an inert substrate, such as silica, and still maintain high polymerization activity. The benefit is largely due to the fact that, when compared to the unsupported metallocenes, the supported metallocene catalysts require a much smaller amount of the MAO co-catalyst to achieve high activity. This reduces the overall cost and decreases the amount of residual co-catalyst in the polymer produced. In general, the MAO is superior to the cocatalyst that forms the discrete cation, developed by Turner and Marks, if it can be used in small quantities, because it is usually less expensive and cleans out the most common catalyst poisons. In addition, the supported heterogeneous catalysts offer better control over the polymer morphology and can be used economically advantageous in volumetric and gas phase polymerization processes. The ability of these catalysts to produce highly stereoregular polymers is critical to their value as catalysts. The origin of this stereoregularity is becoming clearer. It is generally accepted that, in an isotactic polypropylene, the chain growth results result from the 1,2 regioselective insertion of the propylene monomer into the metal atom and the first carbon in the polymer chain. The differentiation between one of the two pro-chemical faces of the propylene monomer in coordination and insertion is believed to be influenced by two separate control mechanisms. The first mechanism is an "enantiomorphic site control", where the steric parts of the ligature influence the orientation of the incoming monomers. The second mechanism is the "chain end control", where the stereochemistry of the last inserted monomer dictates the orientation of the subsequently inserted monomer. According to current beliefs, Spaleck suggests that the two control mechanisms are less separable and calls the "indirect steric control" (see L A Catonguay and A R Rappe, J. Am Chem, Soc 1992, 114 5832). In this mechanism, the 1.2 insertion of the prochiral monomer is mainly influenced by the orientation of at least the 4 or 5 carbon atoms closest to the metal center in the growing polymer chain. The orientation of these carbon atoms in the polymer chain is, in turn, influenced by the geometry of the catalyst ligation. The naphthyl group pendent in the Spaleck catalyst is believed to optimize the influence of the ligation on the polymer chain, thus increasing steric control over the next inserted monomer. Spaleck discusses a 100 percent synergistic effect between the 2,2 '-methyl substituents on the indenyl-cyclopentadienyl ring and the 4,4'-naphthyl substituents on the benzo ring of indenyl. This effect, together with the known importance of the interaction between the 2-methyl substituents and the silicone bridge methyls, combine to produce the delicate balance required to obtain highly active and selective catalysts. Spaleck also notes that the electronic effects in these catalytic systems play an important role. An industrially significant class of catalysts, based on a mono-Cp platform, is disclosed in U.S. Patent No. 5,254,405, and European Patent Application 416,815. These "restricted geometry" catalysts demonstrate a high degree of variability, which produces a polypropylene that can vary from 23 percent of mmmm pentad in a polymer with a ratio of 1: 1 of stereo myr locations, up to 93.4 percent of mmmm pentad in a polymer with more than 98 percent of stereo locations m. Catalysts in this class, which incorporate a fluorenyl group in place of a Cp, can produce a predominantly syndiotactic polypropylene, i the substituent in the nitrogen heteroatom is a cyclohexyl group and isotactic polypropylene if the substituent in the heteroatom is a group of t-butyl. Catalysts of this kind are very good at copolymerizing higher α-olefins with ethylene. It should be noted that the Ti is the Group 4 metal of choice in this class of catalysts. Other catalysts in the cutting edge of the olefin polymerization technology include catalysts based on Cp systems with methylene bridge and fluorenyl ligation, which can also produce isotactic, syndiotactic and isotactic polypropylene, as well as that certain copolymers depend on the presence of several substituents (see JA Ewan et al, J Am Chem Soc 1988, 110, 6255). The impact of the metallocene and, in particular, the metallocene catalysts curved in previous metals in the polyolefin industry has been drastic and unparalleled in any other chemical industry in recent times. The tremendous effort made by the scientific community in this area has allowed the rapid progression of the metallocenes as systems of the Ziegler-Natta model, to the metallocenes, as a viable industrial catalyst in its own right. A number of factors have contributed to this success, including its ability to maintain high activity while supported, as well as high stereoselectivity. Another attractive feature of the metallocenes is the potential to use them as substitutes for "selection" for the existing Ziegler-Natta catalysts. The conditions required for the polymerization with the metallocenes are sufficiently similar to those used with the present catalysts. Some of the advantages of metallocene catalysts are similarly specific to α-olefins, but some general advantages can be identified. Metallocene catalysts exhibit four major advantages, which distinguish them from other polyolefin catalyst systems, with a few exceptions (see LK Johnson et al., J. Am Chem Soc 1995, 117, 6414). First, metallocenes can polymerize a wider variety of vinyl monomers than heterogeneous Ziegler-Natta catalysts, regardless of molecular weight or steric obstruction. This provides opportunities for the polymerization and copolymerization of potentially functionalized olefins, olefins and monomers, in combinations hitherto not accessible with conventional catalyst systems. Second, metallocenes are simple site catalysts, where all sites active in a polymerization are identical. This allows the production of uniform polymers and copolymers with narrow distributions of molecular weights and narrow distributions of the composition. Third, because the chain termination step in the metallocene catalysts is the removal of the β-hydrogen, the resulting polymer contains chains with unsaturated end groups. An unsaturated end group supplies a reactive portion that can be used to functionalize the polymer or for graft polymerization. Finally, the metallocenes can polymerize the olefins with not only high regioselectividd, but also with a very high stereoselectivity. This allows a still increasing degree of control over the polymer microstructure as knowledge of the catalyst / tacticity structure ratio of the polymer increases (see J A Ewen, J Makromol Chem, Macromol Symy 1992, 66, 179). Previous metallocene metal catalysts have dominated the transition away from the more traditional Ziegler-Natta catalyst systems in the polymerization industry of α-olefins, with one notable exception. Group IV metal complexes, 12 e ~, mono-cyclopentadienyl, are excellent catalysts for syndiospecific polymerization of aromatic α-olefin-styrene (and various substituted styrenes), when activated with a co-catalyst, such as MAO (see N Ishihara et al., Macromolecules 1986, 19, 2464). The above mono-cyclopentadienyl catalysts are often referred to as "sandwich media" complexes or "piano stool". Styrene is an α-olefin but, due to its unique properties, it is often treated separately from other olefins. Catalysts that polymerize styrene in a syndiotactic manner have been known since the mid-1980s. Catalysts in addition to the "piano stool" complexes that, when properly activated, promote the syndiotactic polymerization of styrene, include the TiX4f where X is a halide, or an alkoxide or alkyl group. The above catalytic species are also known to promote the highly stereoregular polymerization of certain conjugated dienes, when activated with appropriate co-catalysts (see U.S. Patent 5,023,304). Unlike many polymerizations of catholized α-olefins with curved metallocene, where much is known about the catalytic active species, but not so much about the exact nature of the catalytic species derived from the "piano stool" type complexes. However, most investigations have been carried out on "piano stool" type catalysts with respect to the syndiotactic polymerization of styrene. As a consequence, most of the information regarding the mechanisms and catalytic structures involved in these polymerizations has come from this literature. As mentioned, the catalysts derived from the "piano stool" type compounds are also capable of polymerizing certain types of conjugated dienes. A number of similarities seem to exist between the polymerization of the premiere and the conjugated dienes with the catalysts of the "piano stool" type (see A Zambelli et al, Makromol Chem, Macromol Symp 1991, 48/49, 297). As the use of "piano stool" type catalysts for the purpose of polymerizing conjugated dienes is a relatively new field of organometallic chemistry, not much research has been done in this matter as in the syndiotactic polymerization of styrene. Therefore, a closer inspection of what is known about the active species involved in the polymerization of syndiotactic styrene may harbor some light in the mechanisms and catalytic structures involved in the polymerization of conjugated dienes catalyzed with the "stool" type catalyst. of piano". In the syndiotactic polymerization of styrene, at least with respect to the "piano stool" catalysts, based on titanium, it has been suggested that the active species is an alkyl cation, Ti (III), mono-Cp.

As shown above, a single styrene monomer has been inserted into a 2.1 form in a bond of Ti- (III) -R + and has adopted a structure of? 2-benzyl. The formation of the metal center of Ti (III) from a metal center of Ti (IV) in this type of catalyst has recently been shown by Grassi to take place when Cp * TiR3, where Cp * is pentamethylcyclopentadienyl and R is Me or Bz, is reacted with B (C6F5) 3, at room temperature (252C) in chlorobenzene and toluene, by ESR (see A Grassi et al, Organometallics 1996, 15, 480 and A Grassi et al, Macromol Chem Phys 1995, 196, 1093). In fact, the reduction of Ti (IV) to Ti (III), is shown will be accelerated in the presence of styrene and certain substituted styrenes, but it is important to note that this reduction is not quantitative. The selection of the counterion or co-catalyst in the formation of the Ti (IV) catalyst precursor seems to make little difference. Chien showed by ESR that the species of Ti (III), formed of trihaluro-, trisalcóxido-, etc., the complexes of type stool of piano, when they are reacted with the MAO in a way analogous to the system developed by Kaminsky and Sinn (see U Bueschges and JCW Chien, J Polym Sci, Part A 1989, 27, 1525 and JCW Chien et al Macromolecules 1992, 25, 3199). It should be noted that, if the MAO is the co-catalyst, then R is Me in the previous structure. In general, R is any alkyl substituent transferred to the center of the metal from the alkoxy aluminum cocatalyst. R can also represent the growing polymer chain, after which a number of inserts take place. If the starting material is an alkylated stool-type complex, the addition of B (C6F5) 3 is believed to initially form a discrete complex of Ti (IV) R2 +, which, depending on the conditions, can finally decompose in the species of Ti (III). With respect to the formation of syndiotactic polystyrene (sPS), it is generally accepted that the active species in these systems contain paramagnetic Ti (III) metal centers, which have been red since T (IV). However, the mechanism of this decomposition is not known and at least in the case where B (C6F5) 3 is used as a cocatalyst, it appears to be a solvent monomer, sensitive to temperature. Another evidence that Ti (III) species are operative in this kind of catalyst, comes from the observation that the CpTi (III) Cl2 species work equally as well as the CpTi (IV) Cl3 complexes, as catalyst precursors for the syndiotactic polymerization of styrene. The active species in the structure shown above is a complex of 14 e ~, if by analogy to the polymerization catalysts of the 1,4-diene of Ziegler-Natta, the phenyl ring of the last styrene monomer inserted into the growth polymer coordinates the metal center and a coordination mode? it is assumed for the coordinated styrene monomer (see L Porri et al, Prog Polym Sci 1991, 16, 405). The phenyl ring of the last inserted styrene monomer, when coordinated to the metal center, strongly resembles a part of β2-benzyl.

It should be noted that only a 2, 1 insertion of the styrene will allow this type of interaction (see A Zambelli et al, Makrol Chem Macromol Symp 1995, 89, 373). It is known from molecular orbital calculations that all six carbons in the phenyl ring of a benzyl substituent participate in bonding with the center of the metal although they are commonly referred to as? 2-benzils rather than? 6 - or ? n-benzyl Also, the formation and the spectroscopic identification of the adducts of? - arene, similar to those illustrated in the structure shown above, has been demonstrated (see C. Pellecchia et al, Organometallics 1993, 12, 4473). For example, an arene adduct [Cp * MMe2 (? 6-C6H5Me)] [MeB (C6F5) 3], is formed when Cp * Mme3 is reacted with B (C6F5) 3, in toluene at low temperatures, where M represents Zr or Hf (see D Gillis et al, J Am Chem Soc 1993, 115, 2543). It has been shown that the Cp parent remains attached to the metal center and is part of the active species in these polymerizations, several substituted Cps have also been successfully used in the piano stool-type catalysts for syndiotactic polymerization of styrene. For example, if an indenyl is used in place of Cp in a Ti-based trichloride piano stool-type complex, the following catalyst can be synthesized, IndTiCl3, where Ind is indenyl (see TE Ready et al., Macromolecules 1993, 26, 5822). Ready showed that the indenyl-substituted catalyst is actually superior to the analogous Cp for the formation of the syndiotactic polystyrene. In a point-by-point comparison, the IndTiCls, when activated with variable amounts of MAO, showed a higher, supply and percentage of syndiotacticity compared to the CpTiCl3 activated with the MAO. The improved performance of the catalyst was attributed to the greater ability to donate electrons from the indenyl ring relative to the Cp part (see P G Gassman and C H Winter, J Am Chem Soc 1988, lio, 6130). However, Cp * is known to donate higher electron density to the metal centers when it coordinates to that Cp, but CpTiCl3 and Cp * TiCl3, will perform equally well as the styrene polymerization catalyst when activated with the MAO With respect to sPS activity, the order of catalyst performance seems to be IndTiCl3 > Cp * TÍCl3 = CpTÍCl3 = CpTÍCl2 > CpTÍCl2 * 2THF > Cp2TÍCl2 > CpTiCl. Although Ti (II) species such as Ti (Ph) produce sPs, however with low activity (see A Za bello et al, Macromolecules 1989, 22, 2129). Metallocene catalysts that are capable of polymerizing conjugated dienes are rare. In fact, only the completely studied metallocenes, which can polymerize conjugated dienes are the complete ones of the piano stool type. As explained, these types of catalysts are also capable of polymerizing styrene. In the polymerization of the diene, with respect to the Ti-based piano stool type catalysts, the active species have been proposed to be the following, mono-Cp, Ti (III), 14 e ~, cationic allyl species (see Ricci e al, J Organomet Chem 1993, 451, 67): This is based on some of the ideas discussed above, as well as the mechanism involved in 1,4-diene polymerizations catalyzed by the Ziegler-Natta catalyst and other evidence. In the structure shown above, 1,3-butadiene is used as the conjugated diene. Za belli reveals that CpTiCl3 activated with MAO, as being used to copolymerize butadiene and isoprene, among other things (see A Zambelli et al Macromol Chem Phys 1994, 195, 2623). The polymerizations were catalyzed with 2 mg of CpTiCl3 with an Al: Ti ratio of 1100: 1 to 18BC in 3 ml of toluene. The concentrations of butadiene and isoprene varied, producing a copolymer with different molar ratios of each monomer, as shown below.

In general, butadiene was determined to be more reactive than isoprene in this copolymerization. Nevertheless, almost equal amounts of both monomers can be incorporated in the copolymer product if the concentrations of the monomers are adjusted appropriately. As can be seen, the copolymerization rate decreases sharply with the increasing concentration of isoprene and the concentration of butadiene decreases. For comparison purposes, Zambelli also homopolymerized several dienes and stretched under identical conditions. As shown below. The first three polymerizations were catalyzed by 2 mg of CpTiCl3 activated with MAO, with an Al: Ti ratio of 1000: 1 to 18se in 13 ml of toluene. The fourth operation used 0.005 mg of CpTiCl3 with an Al: Ti ratio of 1.4 x 10 5.

As can be seen, the increase in the reactivities is in the following order: isoprene «styrene < butadiene «4-methyl-l, 3-pentadiene. Recent research by Baird suggests that, under some conditions, styrene can be polymerized by means of a carbocationic mechanism with these types of carterizers. These new results may have implications for dienes and other monomers polymerized with Ti-based piano stool type catalysts, when the co-catalyst is B (C6F5) 3. As mentioned above, the discrete free base alkyl cations can be synthesized from the CpM 3 complexes, where M represents a Group IV metal and R represents an alkyl group, adding B (CsF5) 3 (see U.S. Patent 5,446,117). However, Baird's results published recently in this area indicate that there is a dependence on temperature, solvent and monomers in the type of catalysts present in the solution, which may, therefore, affect the mechanism of the polymerization itself ( see Q Wang et al, Organometallics 1996, 15, 693). In Baird's work, Cp * TiMe3 and B (C6F5) 3 are mixed under various conditions that generate catalysts that appear to produce an atactic polestirene by means of a carbocationic mechanism.

Baird observed that, in polar solvents such as Ch2Cl2, a catalyst is produced that polymerizes styrene to form atactic polystyrene when Cp * TiMe3 and B (CgF5) 3 react at temperatures ranging from 20 to -78QC. In non-polar solvents, such as toluene, however, the same two catalyst components can be combined to form a catalyst that polymerizes styrene, to form the sPS, but only if the polymerization temperature is maintained above 02C. When the polymerization is operated below OCC, only atactic polystyrene is formed. As an explanation of these results, Baird suggests that a species of active catalyst be formed, which promotes the atactic polymerization of styrene by means of a carbocationic mechanism, depending on the polymerization conditions. As mentioned, Grassi showed that Ti (III) species are formed at 25 --- C in chlorobenzene and toluene, when Cp * TiR3, where R is Me or Bz, is reacted with B (C6F5) 3. This is consistent with the general hypothesis that the active species in sPS catalysts with the Ti-based piano stool-type complexes are species of CpTi (III) -R +. However, based on the results of Baird and Grassi, it is almost certain that most Ti-centered species can form and, depending on the conditions of temperature, solvent, and monomer, different species that can become catalysts assets. For example, Baird showed by NMR spectroscopy that, when Cp * TiMß3 and B (CeF5) 3 react in CD2C12, at a low temperature and maintained at low temperatures, the Ti (IV) species [Cp * TiMe2] [MeB (C6F5) 3] which forms initially in this reaction, remains stable and does not decompose in Ti (III) species or other species. When the NMR spectrum is monitored as the temperature increases, Baird noted that the number of new resonances of Cp * and Ti-Me appear, indicating several new species formed. Also, Baird showed that, when Cp * TiMß3 and B (c6 s) 3 are combined at room temperature in CH2C1, ClCH2CH2Cl? or toluene, very active catalysts are formed, which are capable of polymerizing ethylene. The conditions of ambient temperature and Ch 2 Cl as a solvent were not previously noted as conditions capable of forming a catalyst that is suspected to produce atactic polystyrene by means of a carbocationic mechanism. However, ethylene is not easily polymerized by a carbocationic mechanism. Certainly, a possible explanation for these observations is that more than one species of catalyst is formed when Cp * TiMe3 and B (C6F5) 3 react. It is not clear how this information relates to the polymerization of conjugated diene, catalyzed with a complex of piano stool type, based on Ti. B (CeF5) 3 is not used as a co-catalyst in any of the polymerizations of conjugated dienes mentioned herein. Only the MAO is used. The implications can be significant if the complexes formed of the piano stool-type species, based on Ti (IV), activated with MAO, similar to those formed when using B (CeF5) 3, as a co-catalyst (counterion) ), given the proposed similarities between the diene and styrene polymerizations, with this type of catalyst. Evidence suggests that Ti-centered, piano-activated, stool complexes, activated with MAO, do not behave in a similar manner to those activated with B (C6F5) 3, if the reactions are conducted at room temperature or higher (see P Longo et al, Macromol Chem Phys 1995, 196, 3015). In addition Longo showed that, in toluene, even at -17SC, CpTiCl3 activated with MAO, forms syndiotactic polystyrene. Some aspects of the styrene and diene polymerizations catalyzed by the piano stool type complex are less clear and require further investigation. For example, it is known that the styrene inserts in the M-R + bond of the piano stool type complexes, in a manner of 2.1, but other α-olefins, such as propylene, are generally inserted in the bond of M-R +, from the above metal-based metallocenes, in a 1,2 way (see A Zambelli et al, Macromolecules 1987, 20, 2037). With the high vinyl Ziegler-Nata diene polymerization catalysts, an insertion of 2.1 of one of the diene double bonds in the 3-M-allyl species was observed. It is not known whether a similar insertion 2.1 occurs in high vinyl diene polymers, catalyzed with piano stool type complexes. Certainly, questions remain regarding the oxidation state of the active species, especially in the case of Ti, and the possibility that more than one type of catalytic species can be formed. However, clearly Ti is superior to Zr and Hf as a catalyst for both diene and styrene monomers, which may be a reason why Zr-based catalysts have not been studied as much as Ti-based catalysts (see P Longo). et al., Makromol Chem Rapid Commun 1994, 15, 151). It would seem, in the case of styrene, that it does not matter if the catalyst precursor starts with the metal center of Ti (III) or Ti (IV). Ti can, therefore, be superior to Zr because it is more easily reduced, In fact, Cp * ZrBz3 has been shown by ESR does not form species of Zr (III) when it reacts with B (CeF5) 3. However, in the polymerization of the diene, the literature is less clear whether or not the precursors of Ti (III) work as well as the precursors of Ti (IV). The Ti (III) complexes activated with MAO, such as CpTiCl -2THF and "CpTiCL2] n" give diene polymers with the same icroestructrua as diene polymers catalyzed by Ti complexes, starting with Ti in its oxidation state of +4, but with less activity (see G Ricci et al, Makromol Chem Macromol Symp 1995, 89, 383) A possible explanation for this phenomenon may be the difficulty with which Ti (III) complexes are obtained in a pure state, due to its extreme sensitivity to 02 and H20 (for example in the air). Therefore, the difference between the catalyst precursors of T (III) and Ti (IV), may be due to the lack of purity and sensitivity to air, rather than a lack of inherent activity.Finally, in the polymerization of dienes, Ti-based piano stool type catalysts can not always be accurately characterized as "single site" catalysts ", due to the gross weight distributions Cular in these polymerizations can be as high as 4 to 6 (see J. Chien et al, Macromolecules 1992, 25, 3199). With the similarities noted between the mechanisms of styrene and diene polymerizationsIt is not surprising that some research has been conducted in its copolymerization with the piano stool type catalysts, based on the Ti. The majority of this research has been carried out by Zambelli et al (see C.Pallecchia et al, Macromolecules 1992, 25, 4450). In his original work, Zambelli used 2 mg of CpTiCl3 activated with MAO with an Al: Ti ratio of 1100: 1, in 3 ml of toluene, at 40SC, to copolymerize styrene and isoprene. The results are outlined below: It would appear that activated CpTiCl with MAO is capable of copolymerizing styrene and diene isoprene, although conversion is poor and reaction times are long. As can be seen, this catalyst system is more active for the homopolymerization of styrene and isoprene than for the copolymerization of these two monomers. It can further be observed that styrene is much more reactive than isoprene when the two monomers are copolymerized, but the ratio of the monomers can be adjusted to produce a copolymer with an equimolar ratio of styrene and isoprene. The product value of the reactivity ratios, r x r2 - 2.3, is sufficiently low to suggest that the two monomers react in accordance with the related mechanisms and produce an almost random copolymer. Zambelli pointed out that the coordination of isoprene is expected to be stronger than the coordination of styrene to the catalyst. The Ti-? 3-allyl bond of an inserted isoprene is expected to be stronger than the Ti-2-L? -col bridge of an equally inserted styrene. Thus, the coordination of isoprene will be faster and more favored than the coordination of styrene, but the insertion of the isoprene in a Ti-3-allyl bond would be slower than insertion in a Ti-? 2 -benzyl bond. If both coordination and insertion are equal and determine the regime, then the lower reactivity of isoprene compared to styrene in the homopolymerization and the greater reactivity of the copolymerizations of isoprene with styrene could be justified. The molecular weights and the cis content of the copolymers are not supplied. The almost random monomer distribution in the styrene / isoprene copolymers generated in these initial results suggest the investigation of a wider variety of styrene / diene copolymerizations (see A Zambelli et al, Macromol Chem Phys 1994, 195, 2623). Styrene and butadiene were copolymerized with 2 mg of activated CpTiCl3 with MAO, with an Al: Ti ratio of 1100: 1 in 5 ml of toluene at 182C. The concentration of the monomers was varied and the reported results are shown below: In general, all the polymerizations pointed out by Zambelli are reported to produce almost random copolymers under the conditions used. The product value of the reactivity ratios, ri x r2 - 1.6, for the copolymerization of styrene and butadiene is even lower than that observed for styrene and isoprene. It was also reported that the reactivities of the monomers in the homopolymerizations are not parallel to the reactivities in the copolymerization. As previously mentioned, the low homopolymerization rate of isoprene is simply due to the particularly low reactivity of the growing chains that end with an isoprene unit, as compared to the growing chains that end with the styrene units. On the other hand, butadiene is more reactive than styrene both when insertion occurs in the growing chains that end with a butadiene unit and when it occurs in the chains that end with a styrene unit. When the styrene / butadiene copolymerizations are compared under the reaction conditions, where the styrene concentration remains constant, while the butadiene concentration is increased, a real decrease in performance is observed, as shown below: In runs 1-4, 1 mg of CpTiCl3 activated with MAO, with an Al: Ti ratio of 1000: 1, was used as the catalyst in 4.5 ml of toluene to 18se. In step 5, the conditions are identical, except that 3 mg of CpTiCl3 were used in 26 ml of toluene. All five polymerizations were allowed to run for 90 minutes. This decrease in the copolymerization regime caused by the addition of even a small amount of butadiene to styrene, although butadiene is more reactive in both homo- and copolymerizations, is unusual. However, the observation can be justified by assuming that the growing chains that end with the butadiene units are less reactive than the chains that end with the styrene units. The results of the copolymerization of 4-methyl-1,3-pentadiene (4-MPD) and styrene are shown in the following table. These polymerizations are catalyzed with 2 mg of CPTÍCI3 with an Al: Ti ratio of 1100: 1 at 18dC with enough toluene used to bring the total volume of the polymerization to 48 ml.

The 4-MPD is homopolymerized by piano stool type catalysts, based on Ti, in a 1,2 way, which will probably be the reason that it polymerizes so quickly. The exceptionally high reactivity of both the 4-MPD monomer and the growth chains ending with a 4-MPD unit is evident when the molar ratio of styrene u and 4-MPD is compared to the amount of both monomers in the copolymerization .

As a 2.1 insertion of styrene is the only way that a secondary interaction of β2-benzyl can occur, the 2.1 insertion of styrene is likely to occur because this adds stabilization. Similarly, diene insertions are likely to occur in such a way as to increase this coupling potential in secondary interactions, such as the formation of a 3-allyl, except for steric effects. Therefore, the more electrons that release the monomer is when they are coupled in a secondary interaction, once they have been inserted, the less electrophilic and less reactive becomes the center of the Ti metal. Correspondingly, if this intersection of? N (n> 1) can be shifted more towards an interaction of? 1 where there is only a single Ti-C link, for whatever reason, the terminal of the growing chain will be more reactive. This is because the last inserted monomer will be attached less firmly, causing the Ti metal center to be more electrophilic and, as a result, more reactive. Accordingly, the reactivity of the different monomers towards any given reactive chain end increases in the order: styrene < isoprene < butadiene < 4-MPD. This arrangement is roughly in accordance with the increasing nucleophilicity of the monomers.

Principle of the Invention This invention is based on the unexpected discovery that styrene-butadiene block copolymers, having blocks of sPS and blocks of cis-1,4-PBd, can be synthesized by polymerizing styrene and 1,3- butadiene, which uses certain catalytic systems, when the polymerization is conducted at a partial pressure of 1,3-butadiene, which is within the approximate range of 10 to 50 mm of mercury, at a temperature which is within the approximate range of 0 to 100dc These block copolymers are comprised of many blocks of sPS and many blocks of PBd. These block copolymers will normally contain at least 5 blocks of sPS, preferably at least 10 blocks of sPS. This invention reveals, more specifically, styrene-butadiene block copolymers, comprising (a) blocks of syndiotactic polystyrene and (b) blocks of cis-1,4-polybutadiene, in which blocks of cis-1,4-polybutadiene they have a vinyl content of up to 20 percent, where the syndiotactic polystyrene blocks have a content of the syndiotactic microstructure of at least 50 percent, the block copolymer contains at least five blocks of syndiotactic polystyrene and the block copolymer it has a number average molecular weight which is within the approximate range of 10,000 to 700,000. This invention also discloses a process for the synthesis of a styrene-butadiene block copolymer, having blocks of syndiotactic polystyrene, which comprises copolymerizing 1,3-butadiene and styrene, at a temperature which is within the approximate range from 0 to 1002C, and a partial pressure of 1,3-butadiene, which is within the approximate range of 10 to 50 mm of mercury, in which the copolymerization is conducted in the presence of a catalytic system, which is comprised of a catalyst component and a cocatalyst component; wherein the catalyst component is of a structural formula, selected from the group consisting of CPMX3, CpMX, MX4 and MX3, where Cp represents an aromatic compound of the formula C5RnH5_n, in which R represents an alkyl, aryl, alkaryl group, arylalkyl, haloalkyl, haloaryl, haloalkaryl, haloarylalkyl, silylalkyl, silylaryl silylalkaryl, srylarylalkyl, halosilyl-alkyl, halosilylaryl halosilylalkyl, halosilylaryl-alkyl, silylhaloalkyl, silylhaloaryl, silylhalo-alkaryl, halosilylarylalkyl, alkoxy, siloxy, etc. R can also be NR'2 / PR'2, SR 'and BR'2 connected through one or more carbon and / or silicon atoms, with the proviso that if there is more than one carbon atom, they can be saturated or unsaturated, wherein each R1 is the same or different and represents hydride, or is a hydrocarbyl or silyl, optionally substituted with one or more halogen atoms or alkoxy groups and having up to 20 carbon atoms and / or silicon atoms. It should be noted that the R groups may be the same or different and that R may be linked to Cp at one or more sites. In the formula, C5RnH5_n, n represents an integer from 0 to 5. M represents a metal selected from the group consisting of titanium, zirconium and hafnium, and X represents a member selected from the group consisting of hydrogen, halogen, alkyl, aryl, alkaryl, arylalkyl, haloalkyl, haloaryl, haloalkyl, haloarylalkyl, silylalkyl, silylaryl silylalkaryl, srylarylalkyl, halosilyl-alkyl, halosilylaryl halosilylalkyl, halosilylaryl-alkyl, silylhaloalkyl, silylhaloaryl, silylhalo-alkaryl, halosilylarylalkyl, alkoxy, siloxy, NR ', PR', SR 'and BR'. For MX3, X can also be any organic acid containing from 1 to 20 carbon atoms, for example, acetylacetonate, acetate, benzoate, naphthenate, octanoate, neodecanoate, palmitate, stearate, salicaldehyde, trifluoroacetate, etc. It should be noted that the X groups may be the same or different. The X groups can be linked to M in one or more sites. The co-catalyst component is of a formula selected from the group consisting of BR '"' 3 and Z + B" R "p4, where R" represents an alkyl group containing approximately 1 to 10 carbon atoms, wherein R "represents a group of 2,3,4,5,6 - pentafluorophenyl or a 3,5-trifluoromethylphenyl group, where R "" represents a 2,3,4,5,6-pentafluorophenyl group or a 3,5-trifluoromethylphenyl group, or a phenyl group and where Z represents a ammonium salt, a silver atom, or a triphenylmethyl group, with the proviso that, if the catalytic component is MX4, then the co-catalyst component is of the formula: with the proviso that, if the catalytic component is MX3, then the co-catalyst component is of the formula: with further the proviso that, if the co-catalyst component is of the formula BR1"3, then at least one X represents an alkyl group, an aryl group or an alkaryl group; and with the proviso that, if the cocatalyst component is of the formula Z + B ~ R "4, then at least one X represents an alkyl group, an aryl group or an alkaryl group The present invention further discloses a block copolymer , which is comprised of (a) at least one block of syndiotactic polystyrene and (b) at least one block of hydrogenated polybutadiene, wherein the block copolymer has a number average molecular weight within the approximate range of 10,000 to 700,000.

Detailed Description of the Invention The styrene-butadiene block copolymers of this invention are comprised of sPS blocks and cis-1,4-PBd blocks. Blocks of cis-1, 4-PBd will have a vinyl content of up to 20 percent. These cis-1, 4-PBd blocks will typically have a vinyl content (a 1.2 microstructure content) that is within the range of about 7 to 20 percent. These styrene-butadiene block copolymers will typically have an absolute number average molecular weight, which is within the approximate range of ,000 to 700,000. The styrene-butadiene block copolymers will more typically have an absolute number average molecular weight in the approximate range of 20,000 to 500,000, In cases where the styrene-butadiene copolymer has a relatively high bound styrene content, such as 50%. bound percent styrene will typically have a number average molecular weight which is within the approximate range of 25,000 to 50,000. These block copolymers are comprised of more than one polystyrene block and more than one polybutadiene block. The block copolymers will normally contain at least 5 blocks of sPS and more typically will contain at least 10 blocks of sPS. These sPS blocks have a syndiotactic microstructure content of at least 50 percent and typically at least 75 percent. In most cases, the polystyrene blocks will have a syndiotactic microstructure content of at least 90 percent and preferably at least 95 percent. The styrene-butadiene block copolymers of this invention are synthesized by copolymerizing styrene and 1,3-butadiene, under a partial pressure of 1,3-butadiene which is within the approximate range of 10 to 50 mm of mercury, using certain catalytic systems. It is critical for the copolymerization to carry out a partial pressure of the 1,3-butdiene within the range of 10 to about 50 mm of mercury, to obtain the desired block copolymer, having blocks of sPS and blocks of the Cis-1. , 4-PBd. If the partial pressure of the 1,3-butadiene used is too high, a polybutadiene homopolymer will result. However, if the polymerization is carried out under too low a partial pressure of 1,3-butadiene, a polystyrene homopolymer will be produced. In most cases, the copolymerization is carried out using a partial pressure of 1,3-butadiene which is within the approximate range of 15 to 40 mm of mercury. It is usually preferred to use a pressure which is within the approximate range of 20 to 35 mm of mercury. The copolymerizations of this invention can be carried out in a wide temperature range of about 0 to 100 ° C. The copolymerization is typically carried out at a temperature within the approximate range of 5 to 80dC. It is usually preferred to conduct the copolymerization at a temperature which is within the approximate range of 15 to 45 C. The copolymerizations employed in synthesizing the styrene-butadiene block copolymers of this invention will normally be carried out in a hydrocarbon solvent., which may be one or more aromatic, paraffinic or cycloparaffinic compounds. These solvents will normally contain from 4 to 10 carbon atoms per molecule and will be liquid under the conditions of polymerization. Some representative examples of suitable organic solvents include pentane, isooctane, cyclohexane, methylcyclohexane, isohexane, n-heptane, n-octane, n-hexane, benzene, toluene, xylene, ethylbenzene, diethylbenzene, isobutylbenzene, petroleum ether, kerosene, spirits. of petroleum, petroleum naphtha, and the like, alone or in mixture. The polymerizations of this invention can also be conducted as reactions in volumetric phase or gas phase, with the catalyst system being supported or unsupported. In the solution polymerization, there will normally be from 5 to 50 weight percent of monomers in the polymerization medium. Such polymerization media are, of course, comprised of the organic solvent and the monomers. In most cases, it will be preferred that the polymerization medium contains from 20 to 40 weight percent of monomers. It is generally more preferred that the polymerization medium contains from 30 to 35 weight percent of monomers. The catalyst systems employed in the practice of this invention include a catalyst component and a co-catalyst component. The catalytic component is of a structural formula, selected from the group consisting of CpMX3, CpMX2, MX4 and MX3, where Cp represents an aromatic compound of the formula C5RnH5_n, in which R represents an alkyl, aryl, alkaryl, arylalkyl, haloalkyl group, haloaryl, haloalkaryl, haloarylalkyl, silylalkyl, silylaryl silylalkaryl, srylarylalkyl, halosilyl-alkyl, halosilylaryl halosilylalkyl, halosilylaryl-alkyl, silylhaloalkyl, silylhaloaryl, silylhalo-alkaryl, halosilylarylalkyl, alkoxy, siloxy, etc. R can also be NR'2, PR'2, SR 'and BR'2 connected through one or more carbon and / or silicon atoms, with the proviso that if there is more than one carbon atom, they can be saturated or unsaturated, wherein each R1 is the same or different and represents hydride, or is a hydrocarbyl or silyl, optionally substituted with one or more halogen atoms or alkoxy groups and having up to 20 carbon atoms and / or silicon atoms. It should be noted that the R groups may be the same or different and that R may be linked to Cp at one or more sites. In the formula C5RnH5_n, n represents an integer from 0 to 5. M represents a metal selected from the group consisting of titanium, zirconium and hafnium, and X represents a member selected from the group consisting of hydrogen, halogen, alkyl, aryl, alkaryl , arylalkyl, haloalkyl, haloaryl, haloalkyl, haloarylalkyl, silylalkyl, silylaryl silylalkaryl, srylarylalkyl, halosilyl-alkyl, halosilylaryl halosilylalkyl, halosilylaryl-alkyl, silylhaloalkyl, silylhaloaryl, silylhalo-alkaryl, halosilylarylalkyl, alkoxy, siloxy, NR'2, PR'2 , SR 'and BR'2. For MX3, X can also be any organic acid containing from 1 to 20 carbon atoms, for example, acetylacetonate, acetate, benzoate, naphthenate, octanoate, neodecanoate, palmitate, stearate, salicaldehyde, trifluoroacetate, etc. The X groups can be linked to M in one or more sites. It should be understood that the substituent groups attached to the cyclopentadienyl (Cp) may be attached to it at more than one site. The X groups in the catalytic component can be the same or different, saturated or unsaturated, and can be attached to the metal (M) at one or more sites. In the case of CpMX2 and MX3, the metal M is in the oxidation state III and, in the case of CPMX3 and MX4, the metal M is in the oxidation state IV. Some specific representative examples of the compounds that can be used as Cp include: ®§) tsgßi ß AJ YRp, wherein A represents an alkylene group (for example -CH2- or -CH2-CH-) or an arylene group (-C6H4-), where Y represents an oxygen or sulfur atom (in which case m is 1) or nitrogen , boron or phosphorus (in which case m is 2), wherein R represents an alkyl, aryl, alkaryl, arylalkyl, haloalkyl, haloaryl, haloalkaryl, haloarylalkyl, silylalkyl, silylaryl silylcaryl, silylaryl alkyl, halosilylalkyl, halosilylaryl halosilylalcaryl, halosilylarylalkyl, silylhaloalkyl, silylhaloaryl, silylhaloalcaryl, halosilylarylalkyl, alkoxy, siloxy, etc. R may also be NR'2 / PR'2 SR 'and BR'2 connected through one or more carbon atoms and / or silicon, with the proviso that if there is more than one carbon atom, they may be saturated or unsaturated, wherein each R1 is the same or different and represents hydride, or is a hydrocarbyl or silyl, optionally substituted with one or more halogen atoms or alkoxy groups and having up to 20 carbon atoms and / or silicon atoms. It should be noted that the R groups may be the same or different and that R may be attached to Cp at one or more sites and that 1 represents 0 or 1. Some representative examples of specific compounds of this type include: r > V- CH2CH2- O - CH2-CH2 The co-catalyst component has a formula selected from the group consisting of: BR'1 ^ and Z + B ~ Rn ,, 4, where R "represents an alkyl group containing approximately 1 to 10 carbon atoms, in which R '* • represents a group of 2,3,4,5,6 -pentafluorofenilo or a group of 3, 5-trifluoromethylphenyl, where R "" represents a 2,3,4,5,6-pentafluorophenyl group or a group of 3,5-trifluoromethylphenyl, or a phenyl group and wherein Z represents a ammonium salt, an ion ferrocenium ion indenio, cationic derivatives or ferrocene or indene substituted a silver atom or a group of triphenyl ethyl and n represents an integer from 1 to about 40 and preferably from 3 to about 20. In actual practice, R '•' and R "" may be other types of substituents that withdraw electrons, which may be the same or different.In co-catalysts of the MAO type, which are of the formula: R * I - (Al - O &nt; n- * preferably contains from 1 to about 4 carbon atoms, with the methyl groups being more preferred. Some representative examples of the R "'* groups that can be employed in the BR' '' 3 include: Some representative examples of the R "" groups that can be employed in the molecule of Z + TB9- ~ -R, "" include: In X, + tBv-tR, M, 4 the group R "" is preferably the 2,3,4,5,6-pentafluorophenyl group.

If the catalyst component is MX4 or MX3, then the co-catalyst component is of the formula: R * I - (Al - O) n- If the co-catalyst component is of the formula BR '' '3 or Z + B ~ R "" 4, then at least one X represents an alkyl group, an aryl group or an alkaryl group. In most cases, X represents a methyl group or a benzyl group. However, X can be any group that is capable of being extracted from the metal (M). The molar ratio of aluminum, in the co-catalyst component, to the metal, in the catalyst component, will typically be in the range of about 10: 1 to 10,000: 1. The molar ratio of the aluminum in the co-catalyst component to the metal in the catalyst component will preferably be in the range of about 100: 1 to 5,000: 1. It is generally more preferred that the molar ratio of the aluminum, in the co-catalyst component, to the metal, in the catalyst component, is within the approximate range of 400: 1 to 2,000: 1. In commercial applications, the molar ratio of aluminum, in the co-catalyst component, to the metal, in the catalyst component will normally be within the range of 50: 1 to 500: 1. The molar ratio of boron, in the co-catalyst, to the metal, in the catalyst, will typically be within the range of 0.7: 1 up to 1.5: 1. The molar ratio of the boron in the co-catalyst to the metal in the catalyst will more typically be within the range 0.9: 1 to 1.1: 1. It is highly desirable that the molar ratio of the boron in the co-catalyst to the metal in the catalyst be as close as possible to 1: 1. The catalyst system will typically be employed at a level that is within the range of approximately 1 x 10"5 cfm (pairs per 100 parts of monomer) to about 20 cfm.The catalyst will be more typically at a level within the range of lxlO". 4 cfm to 2 cfm and will be used preferably at a level which is within the range of 0.001 to 0.2 cfm. This invention is illustrated by the following examples, which are merely for illustration purposes and should not be considered as limiting the scope of the invention or the manner in which it can be practiced. Unless specifically noted otherwise, parts and percentages are given by weight.

EXAMPLES General Procedures All manipulations were performed under a nitrogen atmosphere, with the use of Schlenk techniques or in a dry box surrounded by an inert atmosphere. Methylalumoxane (MAO), purchased from Witco as a 10 weight percent solution in toluene, was dried under vacuum at 50 C overnight to remove the solvent and free Al (013) 3, and was used in the solid form. The toluene, purchased from Cario Erba, was treated with concentrated H2S? 4, followed by washing with a saturated solution of NaHC? 3 and distilled H20 to remove the thiophene (C4HS). The toluene was then dried over CaCl and distilled off. a metal of Na before being used. The styrene, purchased from Aldrich, was distilled from CaH2 under reduced pressure before being used. The polymerization-grade 1,3-butadiene, purchased from Societa Ossigeno Napoli (S.O.N.), was passed through a column of activated 3Á molecular sieves before being used. The Ti (t-butoxy) was purchased from Aldrich and purified by distillation under reduced pressure. CPTICI3, CpTiFs, Cp * TiF3, Cp * Ti (CH3) 3, Ti (acetylacetonate) 3, and BfCgFs ^, were prepared according to the literature. The p-toluenesulfonyl hydrazide, purchased from Aldrich, (THS) was dried under vacuum at 50 c for 9 hours and stored under nitrogen in a tan glass bottle, before being used. The molecular weights of the polymer were determined by SEC. Glass transition temperatures (Tg) and melting points (Tm) were determined by DSC. The average sequence lengths were calculated based on 13C NMR data and compared to the results of ozonolysis experiments. The microstructures of the polymer were determined by 1H, 13C, VT13C and DEPT NMR experiments and are presented as a mole percent. Note that S = styrene, B = cis-1, -PBd or trans-l, 4-PBd, V = 1,2-butadiene, E = ethylene, b = butene and nd = not detected or not determined.

NMR Characterization of the Syndiotactic Polybutadiene-Polybutadiene Block Copolymers The presence of syndiotactic styrene sequences and the cis-1,4-polybutadiene sequences were determined by 13C NMR (CDC13): triad sindio-SSS (SSiS, 44.3 ppm; SS2S, 41.0 ppm) BBB triad (BCiB and BC4B, 27.4 ppm, BCB and BC3B, 129.8 ppm). The copolymeric nature of these block copolymers was determined by the presence of 13C NMR key resonances (CDCI3), which include: trisodium SSBB (S2SBB, 40.5 ppm; SSjBB, 42.2 ppm; SS2BB, 43.3 ppm; SSCiB, 35.6 ppm; SSB4B , 27.4). Chemical shifts refer to TMS.

NMR Characterization of Syndiotactic Polystyrene-Polybutadiene Block Copolymers The presence of polyethylene sequences was determined by VT 13C NMR (1,1,2,2-tetrachloroethane): EEEE triad (27.78 ppm). The copolymeric nature of these block copolymers was determined by the presence of the 13C NMR (1,1,2,2-tetrachloroethane) key resonances, which include: Triad SSEE (SiSEE, 42.9 ppm; S2SEE, 39.4 ppm; SSiEE 41.6; SS2EE, 41.9 ppm, SSEiE, 35.4 ppm, SSE2E, 25.3 ppm, SSEEi, 27.78 ppm). Chemical shifts are referred to with TMS.

Polymerization Procedure A 250 ml three-necked round bottom flask, dried in an oven, was flooded with dry N until cooled to approximately 25 ° C. Under a positive pressure of N2, the three-neck round-bottomed flask was equipped with a gas-tight mechanical stirring mechanism, a rubber septum and a tap attached to ground glass, dried in the oven, through from which the flask is connected to vacuum, N2 or 1,3-butadiene. Dry toluene (100 ml) was transferred, followed by dry styrene (50 ml), by means of a cannula into the round bottom flask under N2 pressure. A solution of toluene (10 ml) of the desired amount of the solid MAO, prepared in advance in a dry box, using a Schlenk flask dried in an oven, was transferred by means of a cannula into the round bottom flask, with stirring, under pressure of N2. The rubber septum in the round bottom flask, with three necks, was then replaced with a tap attached to ground glass, dried in the oven. This round bottom flask was then placed in a constant temperature bath, adjusted to the desired temperature. The stirred solution was then allowed to reach a thermal equilibrium for 0.5 h. While maintaining an inert environment, the total pressure inside the round-bottomed flask became equal to atmospheric. The desired partial pressure of 1,3-butadiene was achieved in the round bottom flask by introducing 1,3-butadiene at the desired overpressure, with vigorous stirring. After 0.5 h, a solution of toluene (10 ml) of the desired catalyst, prepared in advance in a dry box, using an oven-dried Schlenk flask, was injected into the stirred flask, through the tap, using a glass syringe dried in the oven. Before removing the syringe from the round bottom flask, the exact volume of the upper gas was removed as the catalyst solution was injected. Typically, after 1.0 h, EtOH (approximately 20 ml) was introduced into the round bottom flask to stop the polymerization. The polymerization mixture was then emptied into a vessel with stirred EtOH (approximately 400 ml) acidified with HCl. The coagulated polymer was collected by filtration, washed with EtOH until neutral pH, and a constant weight was vacuum dried.

Hydrosing Procedure A solution of toluene (120 ml) of the desired syndiotactic polybutadiene-polybutadiene block copolymer (2-3% w / w) was treated with 2 equivalents of THS for each butadiene unit, in a round-bottomed flask 250 ml, equipped with a reflux condenser and a Teflon stir bar. The reaction mixture was refluxed for 8 hours, and turned into a yellow solution when the temperature reached 60-80dc. The reaction solution was cooled to about 25 c and filtered. The resulting colorless filtrate was treated with ethanol (300 ml) and the coagulated hydrogenated block copolymer was recovered by filtration. This filtered block copolymer was washed with excess ethanol and hot water and dried under vacuum at 802C at a constant weight.

Example 1 Catalyst: CpTiCl3, 3.0 x 10"5 mol, Cocatalyst: MAO, 1.2 x 10 ~ 2 (molar ratio of Al / Ti = 400); Overpressure of 1,3-butadiene: 22.9 mm Hg; Yield: 0.233 g; Temperature: 15dC; Polymer microstructure: S = 43, B = 50, V = 7, Molecular weight: Mw = 31,700, ri X r2, 562, DSC: Tg = -66.7dC, Tm, 24 &.6BC; Average Sequence: n8 = 14.7, nb = 19.6.

Example 2 Catalyst: CpTiCl3, 3.0 x 10 ~ 5 mol; Cocatalyst: MAO, 1.2 x 10"2 (Al / Ti molar ratio = 400), L, 3-butadiene overpressure: 23.8 mm Hg, Yield: 0.410 g, Temperature: 15SC, Polymer microstructure: S = 15, B = 78, V = 7, Molecular Weight: Mw = 41,400, ri x r2, 285, DSC: Tg = -86.7dc, Tm, nd, Average Sequence Lengths: ns = 4.8, nb = 33.3.

Example 3 Catalyst: CpTiCl3, 3.0 x 10 ~ 5 mol; Cocatalyst: MAO, 1.2 x 10 ~ 2 (molar ratio of Al / Ti = 400); Overpressure of 1,3-butadiene: 24.8 mm Hg; Yield: 1,401 g; Temperature: 15dC; Polymer microstructure: S = 2, B = 83, V = 15; Molecular Weight: Mw = 319,400.

Example 4 Catalyst: CpTiCl3, 3.0 x 10"5 mol; Cocatalyst: MAO, 1.2 x 10" 2 (molar ratio of Al / Ti -400); Overpressure of 1,3-butadiene: 33.8 mm Hg; Yield: 1420 g; Temperature: 15dC; Polymer microstructure: S = 0.3, B = 83, V = 16.7; Molecular Weight: Mw = 501,300.

Example 5 Catalyst: CpTiCl3, 3.0 x 10 ~ 5 mol; Cocatalyst: MAO, 1.2 x 10 ~ 2 (molar ratio of Al / Ti = 400); Overpressure of 1,3-butadiene: 25.7 mm Hg; Yield: 0.860 g; Temperature: 25dC; Polymer microstructure: S = 20, B = 67, V = 13; Molecular Weight: Mw = 367,900.

Example 6 Catalyst: CpTiCl3, 3.0 x 10 ~ 5 mol; Cocatalyst: MAO, 1.2 x 10 ~ 2 (molar ratio of Al / Ti = 400); Overpressure of 1,3-butadiene: 35.7 mm Hg; Yield: 0.73 g; Temperature: 35dC; Polymer microstructure: S = 21, B = 70.3, V = 8.7; Molecular Weight: Mw = 56,090.

Example 7 Catalyst: CPTÍCI3, 3.0 x 10"5 mol; Cocatalyst: MAO, 1.2 x 10" 2 (molar ratio of Al / Ti = 400); Overpressure of 1,3-butadiene: 37.6 mm Hg; Yield: 3.7 g; Temperature: 350C; Polymer microstructure: S = 8, B = 75, V = 17; Molecular Weight: Mw = 170,300.

Example 8 Catalyst: CPTICI3, 3.0 x 10 ~ 5 mol; Cocatalyst: MAO, 1.2 x 10 ~ 2 (molar ratio of Al / Ti -400); Overpressure of 1,3-butadiene: 35.7 mm Hg; Yield: 0.860 g; Temperature: 45SC; Polymer microstructure: S = 90, B-V = 10; Molecular Weight: Mw = 51,794.

Example 9 Catalyst: Cp iF3, 3.0 x 10"5 mol, Co-catalyst: MAO, 1.2 x 10" 2 (molar ratio of Al / Ti = 400); Concentration of 1,3-butadiene: 0.4 M; Performance: 0. 45 g; Temperature: 25fiC; Polymer microstructure: S = 43, B = 43, V = 14.

Example 10 Catalyst: Cp * TiF3, 3.0 x 10"5 mol, Cocatalyst: MAO, 1.2 x 10" 2 (molar ratio of Al / Ti = 400); Concentration of 1,3-butadiene: 0.4 M; Yield: 0.56 g; Temperature: 25dC; Polymer microstructure: S = 7, B = 75, V = 18.

Example 11 Catalyst: Cp * Ti (CH3) 3, 3.0 x 10 ~ 5 mol; Cocatalyst: MAO, 1.2 x 10"2 (Al / Ti molar ratio = 400), 1,3-Butadiene overpressure: 21.8 mm Hg, Yield: 0.057 g, Temperature: l5dC, Polymer microstructure: S = 20, B = 65, V = 15.

Example 12 Catalyst: Ti (acac) 3, 3.0 x 10"5 mol; Cocatalyst: MAO, 1.2 x 10 ~ 2 (molar ratio of Al / Ti = 400); Overpressure of 1,3-butadiene: 20.5 mm Hg; Yield: 0.085 g; Temperature: 15dC; Polymerization time: 2.0 h; Polymer microstructure: S = 39, B - 51, V = 10.

Example 13 Catalyst: Ti (OtBu) 4, 3.0 x 10 ~ 5 mol; Co-catalyst: MAO, 1. 2 x 10"2 (Al mole ratio / Ti = 400); 1,3-butadiene: 26.1 mm Hg; Yield: 0.048 g; Temperature: 15 C; Polymer microstructure: S = 96, B-V = 4 Example 14 Catalyst: Cp * Ti (CH3) 3, 3.0 x 10"5 mol, Cocatalyst: MAO, 1.2 x 10 ~ 2 (Al / Ti molar ratio = 400), 1,3-Butadiene overpressure: 26.3 mm Hg; Yield: 0.057 g; Temperature: 150C; Polymer microstructure: S = 9, B = 78, V = 3.

Example 15 Catalyst: Cp * Ti (CH3) 3, 3.0 x 10"5 mol; Co-catalyst: MAO, 1.2 x 10" 2 (molar ratio of Al / Ti = 400); Overpressure of 1,3-butadiene: 21.9 mm Hg; Yield: 0.03 g; Temperature: 150C; Polymer microstructure: S = 96, B + V = 4.

Example 16 Catalyst: Cp * Ti (013) 3, 3- ° x 10 ~ 5 mol; Cocatalyst: MAO, 1.2 x 10"2 (Al / Ti = 400 mole ratio), 1,3-Butadiene overpressure: 22.6 mm Hg, Yield: 0.6 g, Temperature: 25dC, Polymer microstructure: S = 65 , B = 32, V = 3.

Example 17 Catalyst: Cp * Ti (013) 3, 3 * ° x 10 ~ 5 mol; Cocatalyst: B (CeF5) 3, 3.0 x 10"5 mol, TIBA, 9.0 x 10 ~ 4, Overpressure of 1,3-butadiene: 23.2 mm Hg, Yield: 0.022 g, Temperature: 25dC, Microstructure of the polymer: S = 82, B = 14, V = 4.

Example 18 Catalyst: Cp * Ti (CH3) 3, 3.0 x 10"5 mol, Co-catalyst: B (C6F5) 3, 3.0 x 10" 5 mol, TIBA, 9.0 x 10 ~ 4; Overpressure of 1,3-butadiene: 22.6 mm Hg; Performance: 0. 03 g; Temperature: 25dC; Polymer microstructure: S = 94, B = 4, V = 2.

Example 19 Catalyst: Cp * Ti (0 * 3) 3, 3"° x 10 ~ 5 mol; Cocatalyst: B (C6F5) 3, 3.0 x 10"5 mol, TIBA, 9.0 x 10" 4; Overpressure of 1,3-butadiene: 25.1 mm Hg; Performance: 0. 084 g; Temperature: 30dC; Polymer microstructure: syndiotactic polystyrene (some atactic polystyrene was also detected).

Example 20 Microstructure of block copolymers of syndiotactic polystyrene and polybutadiene: S-70, B = 27, V-3; Polymer microstructure of the hydrogenated block copolymers of syndiotactic polystyrene and resulting polybutadiene: S = 47, E + b = 53; DSC: Tm (styrene), 215dC, Tm (ethylene), 49BC; Average sequence lengths; ns = 20, nE = 11.

Example 21 Microstructure of the block copolymers of syndiotactic polystyrene and polybutadiene: S = 66, B = 26, V = 8; Polymer microstructure of the hydrogenated block copolymers of syndiotactic polystyrene and resulting polybutadiene: S = 45, E + b = 55; DSC: Tm (styrene), 212dc, Tm (ethylene), 60dC; Average sequence lengths; ns = 19, nE = 14.

Example 22 Microstructure of the block copolymers of syndiotactic polystyrene and polybutadiene: S = 24, B = 61, V = 15; Polymer microstructure of the hydrogenated block copolymers of syndiotactic polystyrene and resulting polybutadiene: S = 14, E = 79, b = 7; DSC: Tm (styrene), not detected, Tm (ethylene), 84fiC; Average sequence lengths; na = 2, nE = 132.

Variations of the present invention are possible taking into account the description provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the present invention. Therefore, it will be understood that changes that may be made within the particular embodiments described will be within the intended full scope of the invention, as defined by the following appended claims.

Claims (10)

1. CLAIMS 1. A block copolymer of styrene-butadiene, which is characterized by comprising: (a) syndiotactic polystyrene blocks and (b) blocks of cis-1, 4-polybutadiene which blocks cis-1, 4 polybutadiene having a vinyl content of up to 20 percent, where the syndiotactic polystyrene blocks have a syndiotactic microstructure content of at least 50 percent, wherein the block copolymer contains at least five syndiotactic polystyrene blocks and wherein the block copolymer has a number average molecular weight in the range of 10,000 to 700,000.
2. 2. A block copolymer, which is characterized because it is comprised of: (a) at least one block of syndiotactic polystyrene and (b) at least one hydrogenated polybutadiene block, wherein the block copolymer has an average molecular weight of within of the range of 10,000 to 700,000,
3. 3. A process for the synthesis of block copolymers of styrene-butadiene having syndiotactic polystyrene blocks which is characterized by copolymerizing 1,3-butadiene and styrene at a temperature which is within the approximate range of O to 1000C, and a partial pressure of 1,3-butadiene, which is within the approximate range of 10 to 50 mm of mercury, in which the copolymerization is conducted in the presence of a catalytic system, which is comprised of a catalytic component and a cocatalyst component; wherein the catalyst component is of a structural formula selected from the group consisting of CpMX3, CpMX2, MX4 and MX3 wherein Cp represents an aromatic anion of the formula C5RnH5_n, wherein R represents an alkyl, aryl, alkaryl, arylalkyl, haloalkyl , haloaryl, haloalkaryl, haloarylalkyl, silylalkyl, silylaryl, silylaryl, silylarylalkyl, halosilylalkyl, halosilylaryl, halosilylalkaryl, halosilylarylalkyl, silylhaloalkyl, silylalkaryl, silylhaloalcaryl, halosilylarylalkyl, alkoxy, siloxy, where the R groups can be the same or different and R can be attached to Cp in one or more sites, in the formula C5RnH5_n, n represents an integer from 0 to 5. M represents a metal selected from the group consisting of titanium, zirconium and hafnium, and X represents a member selected from the group consisting of hydrogen, halogen, alkyl, aryl, alkaryl, arylalkyl, haloalkyl, haloaryl, haloalkyl, haloarylalkyl, silylalkyl, silylaryl silylalcaryl or, silylarylalkyl, halosililalquilo, halosililarilo halosililalcarilo, halosilylarylalkyl, sililhaloalquilo, sililhaloarilo, sililhaloalcarilo, halosilylarylalkyl, alkoxy, siloxy, NR'2, PR'2 'SR' and BR '., where, in the formula MX3, X may also be any organic acid containing from 1 to 20 carbon atoms, where the X groups can be the same or different, and in which these X groups can be attached to M at one or more sites. The co-catalyst component is of a formula selected from the group consisting of BR'1 ^ and Z, + tB, ~ "tR" "4, where R" represents an alkyl group containing approximately 1 to 10 carbon atoms, in which R '"represents a group of 2,3,4,5 , 6-pentafluorophenyl or a 3,5-trifluoromethylphenyl group, where R "" represents a 2,3,4,5,6,6-pentafluorophenyl group or a 3,5-trifluoromethylphenyl group, or a phenyl group and where Z represents an ammonium salt, a silver atom, or a triphenylmethyl group, with the proviso that, if the catalytic component is MX4, then the co-catalyst component is of the formula: R'¿A1 - A fl-Of A? R? , - A fl-O-with the proviso that, if the catalytic component is MX3, then the co-catalyst component is of the formula: with further the proviso that, if the cocatalyst component is of the formula BR11 ^, then at least one X represents an alkyl group, an aryl group or an alkaryl group; and with the proviso that, if the cocatalyst component is of the formula Z + B "Rn4, then at least one X represents an alkyl group, an aryl group or an alkaryl group.
4. 4. A styrene-butadiene block copolymer, as defined in claim 1, characterized in that the copolymer has a number average molecular weight in the range of 20,000 to 500,000.
5. 5. A styrene-butadiene block copolymer, as defined in claim 1, characterized in that the copolymer has a number average molecular weight in the range of 25,000 to 50,000.
6. 6. A styrene-butadiene block copolymer, as defined in claim 2, characterized in that the copolymer has a number average molecular weight in the range of 20,000 to 500,000.
7. 7. A process, as defined in claim 3, characterized in that the catalytic component is of the formula CpMX3 and wherein the co-catalyst component is of the formula: R2A1 - (-Al - O -) n- A1R2 in which the temperature is within the range of 5 to 80dC; and where the partial pressure of 1,3-butadiene is within the range of 15 to 40 mm of mercury.
8. 8. A process, as defined in claim 3, characterized in that the catalytic component is of the formula CpMX3 and wherein the co-catalyst component is of the formula: R R2A1 - (-Al - 0 -) n- A1R2 where the partial pressure of 1,3-butadiene is within the range of 10 to 35 mm of mercury; wherein the copolymerization is carried out in the presence of an organic solvent; and where the temperature is within the range of 15 to 45-JC.
9. 9. A block copolymer, which is characterized in that it comprises: (a) syndiotactic blocks which are derivatives of a vinyl aromatic monomer and (b) cis-1,4-polybutadiene blocks, having a vinyl content up to 20% by weight. hundred, wherein these syndiotactic blocks have a syndiotactic microstructure content of at least 50 percent, wherein the block copolymer contains at least five syndiotactic blocks and wherein the block copolymer has a number average molecular weight within the range of 10,000 to 700,000.
10. 10. A block copolymer, as defined in claim 9, wherein the aromatic vinyl monomer is p-methylstyrene.