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to about 1,000,000. Most preferably, the polymer is one having a molecular weight of from about 3,000 to about 200,000 because this offers the best balance between cost, ability to use the mildest curing conditions and achieving good processing behavior. 

In general, when solution anionic techniques are used, conjugated diolefin polymers, polydienes, are prepared by contacting the monomer to be polymerized with an anionic polymerization initiator such as group IA metals, their alkyls, amides, silanolates, napthalides, biphenyls and anthracenyl derivatives. It is preferred to use an organo alkali metal ( such as sodium or potassium) compound in a suitable solvent at a temperature within the range from about -150° C. to about 300° C., preferably at a temperature within the range from about 0° C. to about 100° C. Particu› larly effective anionic polymerization initiators are organo lithium compounds having the general formula: 

<img src='content_image/924510.jpg'>

wherein R is an aliphatic, cycloaliphatic, aromatic or alkyl› substituted aromatic hydrocarbon radical having from 1 to about 20 carbon atoms and n is an integer of 1 to 4. 

Conjugated diolefins which may be polymerized anioni› cally include those conjugated diolefins containing from about 4 to about 24 carbon atoms such as 1,3-butadiene, isoprene, piperylene, methylpentadiene, phenylbutadiene, 3,4-dimethyl- 1,3-hexadiene, 4,5-diethyl-1,3-octadiene and the like. Isoprene and butadiene are the preferred conjugated diene monomers for use in the present invention because of their low cost and ready availability. The conjugated diole› fins which may be used in the present invention include isoprene (2-methyl-1,3-butadiene), 2-ethyl-1,3-butadiene, 2-propyl-1,3-butadiene, 2-butyl-1,3-butadiene, 2-pentyl-1, 3-butadiene(2-amyl-1,3-butadiene), 2-hexyl-1,3-butadiene, 2-heptyl-1,3-butadien 2-octyl-1,3-butadiene, 2-nonyl-1,3- butadiene, 2-decyl-1,3-butadiene,2-dodecyl-1,3-butadiene, 2-tetradecyl-1,3-butadiene, 2-hexadecy 1-1,3-butadiene, 2-isoamyl-1,3-butadiene, 2-phenyl -1,3-butadiene, 2-methyl-1,3-pentadiene, 2-methyl-1,3-hexadiene, 2-methyl-1,3-heptadiene, 2-methyl-1,3-octadiene, 2-methyl-6-methylene-2,7-octadiene (myrcene), 2-methyl- 1,3-nonyldiene. 2-methyl-1,3-decyldiene, and 2-methyl-1,3- dodecyldiene, as well as the 2-ethyl, 2-propyl, 2-butyl, 2-pentyl, 2-hexyl, 2-heptyl, 2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 2-tetradecyl, 2-hexadecyl, 2-isoamyl and 2-phenyl versions of all of these dienes. Also included are 1,3-butadiene, piperylene, 4,5-diethyl- 1,3-octadiene and the like. Di-substituted conjugated diolefins which may be used include 2,3-dialkyl-substituted conjugated diolefins such as 2,3-dimethy 1-1,3-butadiene, 2,3-diethyl-1,3-pentadiene, 2,3-di methyl-1,3-hexadiene, 2,3-diethyl-l,3 -heptadiene, 2.3-dimethyl-1,3-octadiene and the like and 2,3-fl.uoro› substituted conjugated diolefins such as 2,3-clifl.uoro-1,3- butadiene, 2,3-difl.uoro-1,3-pentadiene, 2,3-difl.uoro-1,3- hexadiene, 2,3-difl.uoro-1,3-heptadiene, 2,3-fl.uoro-1,3- octadiene and the like. Alkenyl aromatic hydrocarbons which may be copolymerized include vinyl aryl compounds such as styrene, various alkyl-substituted styrenes, alkoxy› substituted styrenes, vinyl napthalene, alkyl-substituted vinyl napthalenes and the like. 

In general, any of the solvents known in the prior art to be useful in the preparation of such polymers may be used. Suitable solvents, then, including straight---and branched chain hydrocarbons such as pentane, hexane, heptane, octane and the like, as well as, alkyl-substituted derivatives thereof; cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane and the like, as well as alkyl- 

substituted derivatives thereof; aromatic and alkyl› substituted aromatic hydrocarbons such as benzene, naphthalene, toluene, xylene and the like; hydrogenated aromatic hydrocarbons such as tetralin, decalin and the like; linear and cyclic ethers such as methyl ether, methylethyl ether, diethyl ether, tetrahydrofuran and the like. 

More specifically, the polymers of the present invention are made by the anionic polymerization of conjugated diene monomers in a hydrocarbon solvent at a temperature between 0° and 100° C. using an alkyl lithium initiator. 

The termination of living anionic polymers to form func› tional end groups is described in U.S. Pat. Nos. 4,417,029, 4,518,753, and 4,753,991, which are herein incorporated by reference. Of particular interest for the present invention are terminal hydroxyl groups. A monool has one such terminal hydroxy group on only one end of the polymer. A diol has a hydroxy group on each end of the polymer. Polyols are such polymers which have more than two hydroxy groups. Such polymers may be linear polymers with internal hydroxy groups in addition to the terminal hydroxy groups or they may be radial or star polymers having multiple arms of polydiene radiating from a central core and having terminal hydroxy groups thereon. 

Anionic polymerization is often terminated by addition of water to remove the lithium as lithium hydroxide (LiOH) or by addition of an alcohol (ROH) to remove the lithium as a lithium alk:oxide (LiOR). For polymers having terminal functional groups, the living polymer chains are preferably terminated with hydroxyl, carboxyl, phenol, epoxy, or amine groups by reaction with ethylene oxide, carbon dioxide, a protected hydroxystyrene monomer, ethylene oxide plus epichlorohydrin, or the amine compounds listed in U.S Pat No. 4,791,174, respectively. The termination step can result in release of fine particles of lithium bases as described in U.S. Pat. No. 5,166,277 which is incorporated by reference herein. The lithium bases may interfere with hydrogenation of the polymer and preferably are removed. 

Hydrogenation of at least 90%, preferably at least 95%, of the unsaturation in the low molecular weight hydroxy func- tional polydiene polymers is achieved with nickel catalysts as described in U.S. Pat. Nos. Re. 27,145 and 4,970,254 and U.S. patent application Ser. No. 07n85715 which are incor› porated by reference herein. The preferred nickel catalyst is a mixture of nickel 2-ethylhexanoate and triethylaluminum. 

Molecular weights of linear polymers or unassembled linear segments of polymers such as mono-, di-, triblock, etc., arms of star polymers before coupling are conveniently measured by Gel Permeation Chromatography (GPC), where the GPC system has been appropriately calibrated. For polymers of the type described herein, the suitable calibration standards are narrow molecular weight distribu› tion polystyrene polymers. For anionically polymerized linear polymers, the polymer is essentially monodisperse and it is both convenient and adequately descriptive to report the "peak" molecular weight of the narrow molecular weight distribution observed. The peak molecular weight is usually the molecular weight of the main species shown on the chromatograph. For materials to be used in the columns of the GPC, styrene-divinyl benzene gels or silica gels are commonly used and are excellent materials. Tetrahydrofuran is an excellent solvent for polymers of the type described herein. Ultraviolet or refractive index detectors may be used. 

Measurement of the true molecular weight of a coupled star polymer is not as straightforward or as easy to make using GPC. This is because the star shaped molecules do not separate and elute through the packed GPC columns in the same manner as do the linear polymers used for the cali- 

