Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
  • C08F297/02—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type
  • C08F297/026—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type polymerising acrylic acid, methacrylic acid or derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F293/00—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment

Definitions

• This invention relates to certain novel block polymers of the star polymer type, further characterized by the presence of functionalized branches. More particularly, the invention relates to block polymers wherein a plurality of polymerized methacrylate blocks are attached to a central core.
• star block copolymers are generally characterized by a polymerized block of diolefin which serves as a center or core of the block polymer and to which a number, occasionally a large number, of blocks of at least one other polymerized monomer are attached.
• Milkovich, Canadian patent 716,645 discloses the production of such star polymers by sequentially anionically polymerizing an alkenyl-substituted aromatic hydrocarbon and a conjugated alkadiene hydrocarbon to form a "living" intermediate block and coupling at least two of such blocks by the addition of a dialkenyl aromatic hydrocarbon.
• a variety of monomers are said to be useful in the formation of the branches including styrene, alkadienes, vinylpyridines and methacrylate esters. In the latter two cases, ethylene dimethacrylate is said to be used as the bisunsaturated monomer, although no preparation of such polymers is described.
• the polymers of Lutz et al typically exhibit a wide range of molecular weight and there is no terminal functionalization of the branches described except in cases where a living branched polymer is used to polymerize a second dissimilar monomer, ethylene oxide, as the terminal portion of the branches.
• the resulting star polymers have terminal hydroxyl groups at the outer end of the branches to functionalize the polymers.
• the present invention provides a novel class of block polymers of the star type wherein a number of branches of at least one polymerized monomer are attached to a central polymeric core. More particularly, the present invention provides such star polymers wherein at least the terminal portions of the branches are functionalized by a block of polymerized alkyl methacrylate, polymerized through the ethylenic unsaturation of the methacrylate moiety.
• the functionalized star block polymers of the invention are produced by preparing a relatively low molecular weight polymeric initiator by reaction of a metal hydrocarbon compound, typically an alkali metal alkyl, and an anionically polymerizable monomer. This polymeric initiator is then used to crosslink a bisunsaturated monomer to form a crosslinked polymeric block having a plurality of organometallic sites, which crosslinked polymer serves as the core of the ultimate star block polymer product. This core containing metallic sites is utilized to initiate the growth of a number of branches by polymerization of one or more polymerizable monomers including, as a terminal monomer, an alkyl methacrylate.
• the resulting star block polymers are characterized by a relatively uniform molecular weight distribution with functionalized blocks, i.e., blocks of polymeized alkyl methacrylate, as at least the terminal portion of the branches.
• At least one anionically polymerizable monomer is polymerized to a relatively low molecular weight organometallic polymeric initiator by contact with a monofunctional metal hydrocarbon compound polymerization initiator.
• the metal hydrocarbon initiator is suitably a monofunctional alkali metal hydrocarbon compound such as an alkali metal alkyl or an alkali metal aryl.
• Metal alkyls are generally preferred, particularly those alkali metal alkyls comprising lithium and a secondary alkyl moiety. Especially preferred is a sec-butyllithium.
• the anionically polymerizable monomer to be polymerized and thereby form the relatively low molecular weight polymeric initiator is at least one of an alkenyl aromatic compound, e.g., styrene or ⁇ -methylstyrene, a conjugated alkadiene, e.g., butadiene or isoprene, or a vinylpyridine. It is useful on some occasions to employ more than one anionically polkymerizable monomer, polymerized sequentially or copolymerized, in the preparation of the relatively low molecular weight organometallic polymerization initiator. In most instances, however, a single anionically polymerizable monomer is used to produce the initial polymeric initiator. Particularly good results are obtained when the anionically polymerizable monomer is an alkenyl aromatic compound such as styrene or a conjugated alkadiene such as isoprene.
• an alkenyl aromatic compound such as styrene or a
• the polymerization to produce the initial polymeric initiator is conducted by conventional methods as by contacting the at least one anionically polymerizable monomer and the alkali metal hydrocarbon compound in a suitable reaction solvent under moderate reaction conditions.
• Hydrocarbon reaction solvents particularly cycloaliphatic hydrocarbon solvents such as cyclohexane are suitable as reaction solvents. It is useful on some occasions to employ a reaction solvent of greater polarity and in such instances a mixed solvent, often a mixture of cyclohexane and a polar co-solvent, e.g., an ether co-solvent such as diethyl ether or tetrahydrofuran, is used.
• the use of cyclohexane or cyclohexane-diethyl ether as reaction solvent is preferred.
• the polymerization temperature is moderate, for example from about 10° C. to about 60° C. and it is often useful to conduct this polymerization at ambient temperature.
• the reaction pressure is a pressure sufficient to maintain the reaction mixture in a liquid phase. Typical reaction pressures are from about 0.8 atmospheres to about 5 atmospheres.
• Control of the molecular weight of the resulting polymeric species is achieved by conventional methods as by controlling the ratio of metal hydrocarbon compound and anionically polymerizable monomer.
• the resulting polymeric species is conventionally termed a living polymer because of the presence therein of an organometallic site and will preferably have a molecular weight less than about 2000 and often on the order of about 1000.
• This polymeric species itself a polymerization initiator because of the organometallic sites, is used to crosslink a bisunsaturated monomer to form the block polymeric moiety which serves as the central portion or core of the star block polymer of the invention.
• a variety of bisunsaturated monomers are useful in the production of the core of the star block polymers of the invention but good results are obtained through the use of a di(alkenyl) aromatic compound of up to 20 carbon atoms and up to 2 aromatic rings.
• di(alkenyl) aromatic compounds are divinylbenezene, divinyltoluene, divinylbiphenyl, divinylnaphthalene, diisopropenylbenzene, diisopropenylbiphenyl and diisobutenylbenzene.
• Divinyl aromatic compounds are preferred as the bisunsaturated monomer and particularly preferred is divinylbenzene.
• the crosslinking of the bisunsaturated monomer with the polymeric initiator is conducted most easily in the medium in which the initiator is produced by adding the bisunsaturated monomer to the product mixture containing the polymeric initiator.
• the use of the same or similar reaction conditions and reaction solvent are suitable for the crosslinking reaction to form the core of the ultimate star block polymer.
• the crosslinked bisunsaturated monomer product which results is a rather small, tightly-crosslinked polymeric moiety having a plurality of organometallic sites, the number of which depends in part on the ratio of bisunsaturated monomer and the polymeric initiator utilized in the crosslinking process.
• the polymeric core also has, attached thereto, moieties of the polymeric initiator which served as the crosslinking or polymerization agent. It is from the oranometallic sites of this crosslinked core that the methacrylate-containing branches are grown.
• the star block polymers of the invention therefore comprise the core of crosslinked bisunsaturated monomer and attached thereto relatively low molecular weight polymeric species derived from the polymeric initiator and a plurality of functionalized branches incorporating at least a terminal block of polymerized alkyl methacrylate.
• the functionalized branches are homopolymeic alkyl methacrylate branches wherein the alkyl group independently has up to 30 carbon atoms, preferably up to 20 carbons.
• Such homopolymeric functionalized branches result from block polymerization of alkyl methacrylate, the polymerization being through the ethylenic unsaturation of the methacrylate moiety, employing the organometallic sites of the crosslinked core as the anionic polymerization initiator to grow a plurality of polymerized alkyl methacrylate branches on the crosslinked core.
• the alkyl methacrylate esters which are polymerized according to this modification include methyl methacrylate, ethyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, sec-amyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate and octadecyl methacrylate.
• the polymeric core is contacted with alkyl methacrylate to produce the homopolymeric alkyl methacrylate branches.
• alkyl methacrylate will in part depend upon the particular nature of the star block polymer desired. However, the production of polymerized alkyl methacrylate branches wherein the alkyl is primary and of few carbon atoms is relatively difficult because of the rather low reaction temperatures that are required to produce the polymerized alkyl methacrylate branches. alternatively, the production of polymerized alkyl methacrylate branches wherein the alkyl moiety is a higher alkyl moiety is also difficult because of the relatively inactive character of such alkyl methacrylates and the difficulty of readily obtaining the desired alkyl methacrylate monomer.
• the preferred alkyl methacrylates for forming the star block polymer of methacrylate-containing branches is a branched-butyl methacrylate, i.e., sec-butyl methacrylate or t-butyl methacrylate.
• the star block polymers resulting from use of these methacrylates are preferred products because of the desirable properties thereof but also because of the relative ease of production.
• Star block polymers incorporating other alkyl methacrylate moieties are produced directly from the corresponding alkyl methacrylate but it is often desirable to produce such polymers by initially employing a branched-butyl methacrylate to produce a star block polymer having branched-butyl methacrylate branches and subsequently trans-esterifying the initial star block polymer product to incorporate the desired alkyl moieties.
• suitable reaction conditions typically include a reaction temperature from about -80° C. to about 80° C. with the lower portion of that range being preferred for polymerization of sec-butyl methacrylate and the higher portion of the range being preferred for t-butyl methacrylate.
• the polymerization pressure is suitably sufficient to maintain the reaction mixture in a liquid phase, typically up to about 5 atmospheres.
• the functionalized branches grown from the core contain an initial or internal segment or block of polymerized anionically polymerizable monomer and a second or terminal portion of polymerized alkyl methacrylate.
• the organometallic sites of the crosslinked core are used to initiate the growth from the core of the segments of polymerized anionically polymerizable monomer which should not be of greater length than the length of the polymeric initiator used to prepare the crosslinked core.
• the resulting block polymer, containing organometallic sites on the branches thereof, is used to initiate the growth of the terminal segments of polymerized alkyl methacrylate.
• the anionically polymerizable monomer employed as precursor of the internal, non-functionalized segment is the same monomer or is a different monomer than that used to produce the polymeric initiator for the crosslinking of the bisunsaturated monomer to form the central core.
• Preferred anionically polymerizable monomers for producing any non-functionalized portion of the branches of the star block polymer are alkenyl aromatic compounds such as styrene and conjugated alkadienes such as isoprene.
• the crosslinked polymeric core containing organometallic sites is suitably reacted in situ with the anionically polymerizable monomer at a reaction temperature of from about 10° C. to about 60° C. and a reaction pressure of up to about 5 atmospheres.
• the resulting star block polymer intermediate containing a plurality of polymerized anionically polymerizable monomer branches with organometallic sites is then reacted in situ with alkyl methacrylate, preferably branched-butyl methacrylate, as described above, to produce the desired star block polymer having alkyl methacrylate-containing branches.
• the polymeric products of the invention are block polymers of the star type characterized by a central core of crosslinked bisunsaturated monomer and a plurality, e.g., more than one and preferably of at least 3 functionalized branches attached thereto wherein at least the outer portion of substantially each functionalized branch is poly(alkyl methacrylate) polymerized through the ethylenic unsaturation of the methacrylate moiety and wherein each alkyl independently has up to 30 carbon atoms.
• non-functionalized branches i.e., branches not containing at least a terminal portion of polymerized alkyl methacrylate are present, resulting from initiation of crosslinking by the polymeric initiator and premature chain termination during the production of an intended internal, non-functionalized segment of a branch. Nevertheless, a substantial proportion of the branches are functionalized by the presence of an at least terminal portion of polymerized alkyl methacrylate.
• the molecular weight of the star block polymers of the invention will vary with the choice of reaction conditions, reaction solvent and the relative proportions of monomeric reactants as well a determined in part by whether the functionalized branches are homopolymeric or contain an internal portion of polymerized anionically polymerizable monomer.
• the star block polymers of particular interest have a molecular weight from about 20,000 to about 2,000,000 and particularly from about 50,000 to about 1,000,000. It should be understood that the precise molecular weight will vary from molecule to molecule and that the above values are average values. It is, however, characteristic of the star block polymers of the invention that the polymer has a rather narrow molecular weight distribution.
• the star block polymers are therefore represented by the formula ##STR1## wherein C is the block of crosslinked bisunsaturated monomer, A independently is a block of polymerized anionically polymerizable monomer, M is a block of polymerized alkyl methacrylate, wherein each alkyl independently has up to 30 carbon atoms, polymerized through the ethylenic unsaturation of the methacrylate moiety, r is 0 or 1, s is an average number from about 3 to about 50, more frequently from about 10 to about 30, and t is a number up to 50 which is equal to or greater than s.
• the percentage of the molecular weight of the molecule attributable to the central core, C is no more than about 10% and preferably no more than about 2%.
• the percentage of polymerized alkyl methacrylate is, of course, 100% in the case of a homopolymeic branch and less in the case where the branch contains an internal segment of polymerized anionically polymerizable monomer.
• the percentage of molecular weight of the functionalized branches attributable to polymerized alkyl methacrylate is at least about 50% and preferably at least about 90%. Homopolymeric branches of polymerized alkyl methacrylate are particularly preferred.
• the star block polymers of the invention are members of the class of materials termed thermoplastic rubbers in that the polymers exhibit elastomeric properties at ambient temperature and yet demonstrate thermoplastic character at moderately elevated temperatures.
• the polymers are therefore useful in a number of applications conventional for thermoplastic elastomers, particularly including adhesive formulations.
• the star block polymers are useful as viscosity index improvers for motor oil and other hydrocarbon fluids.
• a round-bottom flask of 500 ml capacity was flushed with nitrogen and 250 ml of cyclohexane was added. Stirring was initiated as the contents of the flask were warmed, under reflux, to 40° C. under nitrogen and 50 ml of diethyl ether were added. Two drops of diphenylethylene were added as an indicator and the solution was titrated with s-butyllithium until a dark yellow color was attained. After the addition of 1.5 ml of s-butyllithium, 1.0 ml of divinylbenzene was added, dropwise, as the color of the solution turned dark red-purple. The solution was stirred for 20 minutes as the color changed to a dark rust and a precipitate formed.
• a glass polymerization bottle was equipped with a mechanical stirrer and a syringe through which chemicals were added.
• the bottle was flushed with and maintained under nitrogen. After the addition of 200 ml of cyclohexane, stirring was initiated.
• To the bottle were added 1.0 ml of N,N,N',N'-tetramethylethylenediamine and 4 drops of diphenylethylene.
• the solution was titrated with a s-butyllithium to a light orange color which did not change when an additional 1.5 ml of s-butyllithium were added.
• a glass polymerization bottle equipped with a stirrer was flushed with nitrogen and 200 ml of cyclohexane about 5.0 ml of diethyl ether were added. Stirring was initiated and after the addition of 4 drops of diphenylethylene as indicator the solution was titrated with s-butyllithium to an orange color. An additional 1.5 ml of s-butyllithium was added and the resulting solution was stirred for 15 minutes. As stirring continued, 3.2 ml of isoprene was added dropwise. One milliliter of divinylbenzene was then added as the color of the solution turned blood red.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Inorganic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Graft Or Block Polymers (AREA)
• Polyamides (AREA)
• Polyesters Or Polycarbonates (AREA)
• Polymers With Sulfur, Phosphorus Or Metals In The Main Chain (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

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Citations (15)

• 1991
  • 1991-05-27 JP JP3121398A patent/JP2975454B2/ja not_active Expired - Lifetime
  • 1991-05-27 CA CA002043307A patent/CA2043307A1/fr not_active Abandoned
  • 1991-05-27 KR KR1019910008680A patent/KR910020056A/ko not_active Withdrawn
  • 1991-05-28 DK DK91201292.9T patent/DK0459588T3/da active
  • 1991-05-28 EP EP91201292A patent/EP0459588B1/fr not_active Expired - Lifetime
  • 1991-05-28 DE DE69111697T patent/DE69111697T2/de not_active Expired - Fee Related
  • 1991-05-28 AT AT91201292T patent/ATE125828T1/de not_active IP Right Cessation
• 1992
  • 1992-09-08 US US07/942,019 patent/USH1730H/en not_active Abandoned

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