Patent Application
20090299013
The instant invention relates to a process for the preparation of star and block-copolymers, which are prepared by controlled free radical polymerization using epoxy-functionalized alkoxyamines and multifunctional compounds capable of reacting with the epoxy group.
Well-defined star polymers are typically prepared by various living polymerization techniques. There are three basic synthesis routes for star polymers. One is the so called core-first method, which uses a multifunctional initiator to initiate the polymerization of monomers, whereby the number of arms is determined by the number of initiating sites on the initiator molecule. This is for example described by J. Ueda, M. Kamigaito, M. Sawamoto; Macromolecules 31; 6762 (1998).
The arm-first technique involves the synthesis of preformed arms, usually through living polymerization, followed by reaction with a multifunctional linking agent as for example described by S. Kannaoka, M. Sawamoto, T. Higashimura; Macromolecules 24; 2309 (1991) and by R. T. A. Mayadunne, J. Jeffery, G. Moad, E. Rizzardo; Macromolecules 36; 1505 (2003).
The third method is a slight variation of the arm-first technique, which sometimes is also termed the “nodule” method. In this method, the reactive macroinitiator (arms) produced by a living polymerization technique are cross-linked by a divinyl reagent to form star polymers, as for example described by X. Zhang, J. H. Xia, K. Matyjaszewski; Macromolecules 33, 2340 (2000).
A further approach is the grafting of epoxy-terminated oligomers onto functionalized polymers leading also to star and comb-copolymers, as for example disclosed in WO 04/069887.
It has now been found that starting with epoxy-functional alkoxyamines it is possible to firstly polymerize ethylenically unsaturated monomers in a controlled way and thereby introducing the reactive epoxy group into the polymer backbone. In a second step the epoxy group can be reacted with selected multifunctional compounds in a polymer analogous reaction, giving finally highly branched star polymers. It is, however, also possible to firstly react the epoxy-functional alkoxyamines with a multifunctional compound thereby introducing branching in the first reaction step. As a second step controlled radical polymerization in the presence of an ethylenically unsaturated monomer can be carried out. In both cases a broad range of highly branched star polymers is accessible.
Star branched copolymers of narrow molecular weight distribution have unique rheological properties and behave significantly different from linear polymer melts. These differences in the mechanical and solubility properties are due to different dynamics of star (co)polymers compared to their linear counterparts. Star-shaped polymers may serve as surface-active agents, compatibilizers, thermoplastic elastomers, materials for shaping parts and emulsifiers.
One aspect of the invention is a method for the preparation of a star polymer or copolymer comprising
a1) polymerising in a first step an ethylenically unsaturated monomer in the presence of an initiator compound of formula (I)
wherein L is a linking group selected from the group consisting of C1-C18alkylene, phenylene, phenylene-C1-C18alkylene, C1-C18alkylene-phenylene, C1-C18alkylene-phenylene-oxy and C5-C12cycloalkylene;
Rp and Rq are independently tertiary bound C4-C28alkyl groups which are unsubstituted or substituted by one or more electron withdrawing groups or by phenyl; or
Rp and Rq together form a 5 or 6 membered heterocyclic ring which is substituted at least by 4 C1-C4alkyl groups and which may be interrupted by a further nitrogen or oxygen atom; and in a second step
b1) reacting the polymer obtained in step a) with a compound of formula R1(X)n, wherein R1 is C1-C24alkyl, C5-C12cycloalkyl, phenyl, naphthyl, C7-C15phenylalkyl or is the residue of a phosphor containing acid;
X is a radical derived from glycerol or from a polyvinylalcohol
R is C1-C24alkyl and n is a number from 3-10;
or
a2) reacting in a first step a compound of formula I with a compound of formula R(X)n as defined above, and
b2) reacting the multifunctional initiator compound, obtained in step a2) with an ethylenically unsaturated monomer in a polymerization reaction.
For example the compound of formula (I) is of formula (II)
R1, R2, R3 and R4 are independently of each other C1-C4alkyl;
R5 is hydrogen or C1-C4alkyl;
R′6 is hydrogen and R6 is H, OR10, NR10R11, —O—C(O)—R10 or NR11—C(O)—R10;
R10 and R11 independently are hydrogen, C1-C18alkyl, C2-C18alkenyl, C2-C18alkinyl or C2-C18alkyl which is substituted by at least one hydroxy group or, if R6 is NR10R11, taken together, form a C2-C12alkylene bridge or a C2-C12-alkylene bridge interrupted by at least one O atom; or
R6 and R′6 together are both hydrogen, a group ═O or ═N—O—R20 wherein
R20 is H, straight or branched C1-C18alkyl, C3-C18alkenyl or C3-C18alkinyl, which may be unsubstituted or substitued, by one or more OH, C1-C8alkoxy, carboxy, C1-C8alkoxycarbonyl;
C5-C12cycloalkyl or C5-C12cycloalkenyl;
phenyl, C7-C9phenylalkyl or naphthyl which may be unsubstituted or substituted by one or more C1-C8alkyl, halogen, OH, C1-C8alkoxy, carboxy, C1-C8alkoxycarbonyl;
—C(O)—C1-C36alkyl, or an acyl moiety of a α,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of an aromatic carboxylic acid having 7 to 15 carbon atoms;
—SO3−Q+, —PO(O−Q+)2, —P(O)(OR2)2, —SO2—R2, —CO—NH—R2, —CONH2, COOR2, or Si(Me)3, wherein Q+ is H+, ammonium or an alkali metal cation; or
R6 and R6′ are independently —O—C1-C12alkyl, —O—C3-C12alkenyl, —O—C3-C12alkinyl, —O—C5-C8cycloalkyl, —O-phenyl, —O-naphthyl, —O—C7-C9phenylalkyl; or
R6 and R′6together form one of the bivalent groups —O—C(R21)(R22)—CH(R23)—O—, —O—CH(R21)—CH22—C(R22)(R23)—O—, —O—CH(R22)—CH2—C(R21)(R23)—O—, —O—CH2—C(R21)(R22)—CH(R23)—O—, —O-o-phenylene-O—, —O-1,2-cyclohexyliden-O—, —O—CH2—CH═CH—CH2—O— or
wherein
R21 is hydrogen, C1-C12alkyl, COOH, COO—(C1-C12)alkyl or CH2OR24;
R22 and R23 are independently hydrogen, methyl ethyl, COOH or COO—(C1-C12)alkyl;
R24 is hydrogen, C1-C12alkyl, benzyl, or a monovalent acyl residue derived from an aliphatic, cycloaliphatic or aromatic monocarboxylic acid having up to 18 carbon atoms; and
R7 and R8 are independently hydrogen or C1-C18alkyl.
C1-C18alkyl can be linear or branched. Examples are methyl, ethyl, propyl, isopropyl, butyl, 2-butyl, isobutyl, t-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t-octyl, nonyl, decyl, undecyl, dodecyl or octadecyl. Where up to C36alkyl is possible, C1-C18alkyl is preferred.
Alkyl substituted by a group —COOH is for example CH2—COOH, CH2—CH2—COOH, (CH2)3—COOH or CH2—CHCOOH—CH2—CH3
Hydroxyl- or alkoxycarbonyl substituted C1-C18alkyl can be, for example, 2-hydroxyethyl, 2-hydroxypropyl, methoxycarbonylmethyl or 2-ethoxycarbonylethyl.
Alkenyl having from 2 to 18 carbon atoms is a branched or unbranched radical, for example propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2,4-pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, isododecenyl.
Alkinyl having from 2 to 18 carbon atoms is a branched or unbranched radical, for example propinyl, 2-butinyl, 3-butinyl, isobutinyl, n-2,4-pentadiinyl, 3-methyl-2-butinyl, n-2-octinyl, n-2-dodecinyl, isododecinyl.
Examples of alkoxy are methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, pentoxy, isopentoxy, hexoxy, heptoxy or octoxy.
C7-C9-phenylalkyl is for example benzyl, α-methylbenzyl, α,α-dimethylbenzyl or 2-phenylethyl, benzyl is preferred.
C5-C12cycloalkyl is for example cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl or cyclooctyl.
C5-C12cycloalkenyl is for example 3-cyclopentenyl, 3-cyclohexenyl or 3-cycloheptenyl.
Examples of a monocarboxylic acid having up to 18 carbon atoms are formic acid, acetic acid, propionic acid, the isomers of valeric acid, methyl ethyl acetic acid, trimethyl acetic acid, capronic acid, lauric acid or stearic acid. Examples for unsaturated aliphatic acids are acrylic acid, methacrylic acid, crotonic acid, linolic acid and oleic acid.
Typical examples of cycloaliphatic carboxylic acids are cyclohexane carboxylic acid or cyclopentane carboxylic acid.
Examples of aromatic carboxylic acids are benzoic acid, salicylic acid or cinnamic acid.
Halogen is F, Cl, Br or I.
C1-C18alkylene is a branched or unbranched radical, for example methylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, decamethylene or dodecamethylene.
C2-C12alkylene bridges interrupted by at least one O atom are, for example, —CH2—O—CH2—CH2, —CH2—O—CH2—CH2—CH2, —CH2—O—CH2—CH2—CH2—CH2—, —CH2—O—CH2—CH2—O—CH2—.
Alkoxycarbonyl is for example methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl.
For instance R1, R2, R3, R4 are methyl, or R1 and R3 are ethyl and R2 and R4 are methyl, or R1 and R2 are ethyl and R3 and R4 are methyl.
For example R5 is hydrogen or methyl.
Preferably R′6 is hydrogen and R6 is H, OR10, NR10R11, —O—C(O)—R10 or NR11—C(O)—R10;
R10 and R11 independently are hydrogen, C1-C18alkyl, C2-C18alkenyl, C2-C18alkinyl or C2-C18alkyl which is substituted by at least one hydroxy group or, if R6 is NR10R11, taken together, form a C2-C12alkylene bridge or a C2-C12-alkylene bridge interrupted by at least one O atom; or
R6 and R′6 together are both hydrogen, a group ═O or ═N—O—R20 wherein
R20 is H or straight or branched C1-C18alkyl.
In another preferred embodiment R6 and R′6 together form one of the bivalent groups —O—C(R21)(R22)—CH(R23)—O—, —O—CH(R21)—CH22—C(R22)(R23)—O—, —O—CH(R22)—CH2—C(R21)(R23)—O—, —O—CH2—C(R21)(R22)—CH(R23)—O— and R21, R22 and R23 have the meaning as defined above.
Specific compounds are given in Table A
The compounds of formula II and in particular the compounds given in Table A are known and may be prepared as described in WO 99/46261, WO 02/48109 or U.S. Pat. No. 5,721,320.
For example the ethylenically unsaturated monomer or oligomer is selected from the group consisting of styrene, substituted styrene, conjugated dienes, vinyl acetate, vinylpyrrolidone, vinylimidazole, maleic anhydride, (alkyl)acrylic acidanhydrides, (alkyl)acrylic acid salts, (alkyl)acrylic esters, (meth)acrylonitriles, (alkyl)acrylamides, vinyl halides and vinylidene halides.
In particular the ethylenically unsaturated monomers are styrene, methylacrylate, ethyl-acrylate, butylacrylate, isobutylacrylate, tert. butylacrylate, hydroxyethylacrylate, hydroxy-propylacrylate, dimethylaminoethylacrylate, methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, dimethyl-aminoethyl(meth)acrylate, acrylonitrile, acrylamide, methacrylamide or dimethylaminopropyl-methacrylamide.
Particularly the ethylenically unsaturated monomers are isoprene, 1,3-butadiene, α-C5-C18alkene, styrene, α-methyl styrene, p-methyl styrene or a compound of formula CH2═C(Ra)—(C=Z)—Rb, wherein Ra is hydrogen or C1-C4alkyl, Rb is NH2, O−(Me+), glycidyl, unsubstituted C1-C18alkoxy, C2-C100alkoxy interrupted by at least one N and/or O atom, or hydroxy-substituted C1-C18alkoxy, unsubstituted C1-C18alkylamino, di(C1-C18alkyl)amino, hydroxy-substituted C1-C18alkylamino or hydroxy-substituted di(C1-C18alkyl)amino, —O—CH2—CH2—N(CH3)2 or —O—CH2—CH2—N+H(CH3)2 An−;
An− is a anion of a monovalent organic or inorganic acid;
Me is a monovalent metal atom or the ammonium ion.
Z is oxygen or sulfur.
Examples for Ra as C2-C100alkoxy interrupted by at least one O atom are of formula
wherein Rc is C1-C25alkyl, phenyl or phenyl substituted by C1-C18alkyl, Rd is hydrogen or methyl and v is a number from 1 to 50. These monomers are for example derived from non ionic surfactants by acrylation of the corresponding alkoxylated alcohols or phenols. The repeating units may be derived from ethylene oxide, propylene oxide or mixtures of both.
Further examples of suitable acrylate or methacrylate monomers are given below.
An−, wherein An− and Ra have the meaning as defined above and Re is methyl, benzyl or benzoylbenzyl. An− is preferably Cl−, Br− or −O3S—O—CH3.
Further acrylate monomers are N
Me+, Me+ is an alkali metal cation or the ammonium cation.
Examples for suitable monomers other than acrylates are
Preferably Ra is hydrogen or methyl, Rb is NH2, gycidyl, unsubstituted or with hydroxy substituted C1-C4alkoxy, unsubstituted C1-C4alkylamino, di(C1-C4alkyl)amino, hydroxy-substituted C1-C4alkylamino or hydroxy-substituted di(C1-C4alkyl)amino; and
Z is oxygen.
For example in the compound of formula R1 (X)n R1 is C1-C12alkyl, C5-C12cycloalkyl or phenyl;
R is C1-C12alkyl and n is a number from 3-6.
Particularly useful are the following compounds R1(X)n:
For example the reaction steps a2) and b1) are carried out at a temperature between 20° C. and 120° C.
The coupling steps (a2, b1) between epoxy-functionalized NOR or epoxy-functionalized/NO-terminated-oligomer, cooligomer, polymer or copolymer and the multifunctional compound can be carried out in bulk or solution, containing 10-90% (by vol.) solvent. Suitable solvents include tetrahydrofurane, benzene, toluene, acetonitrile, dimethylformamide, chlorinated solvents and mixtures thereof.
Preferably the temperature of the coupling steps is between 50° C.-120° C., more preferably between 60° C.-110° C. and most preferably between 70° C.-100° C.
Preferably the coupling step is carried out at a temperature below the cleavage temperature of the NOR bond, where polymerization is initiated. This cleavage temperature depends on the structure of the selected NOR compound. For example the tetramethyl piperidines given in Table A can be processed at higher temperatures as compared to the dimethyl, diethyl substituted compound no. 104.
Typical reaction times range from 1-72 h, more preferably 1-48 h and most preferably from 3-24 h.
The reaction is usually carried out under atmospheric pressure.
The isolation of the star copolymer depends on its molecular structure. Residual monomers can be removed in vacuo at temperatures not exceeding 100° C. It is also possible to precipitate the polymer or to extract residual monomers with appropriate solvents.
Preferably the reaction steps a1) and b2) are carried out at a temperature between 80° and 160° C.
As already mentioned the alkoxyamine bond cleaves at elevated temperature and radical polymerization is initiated. Preferably the polymerization temperature is from 80° C. to 140° C., in particular from 100° C. to 140° C.
For example in step a1) the compound of formula I is present in an amount from 0.01 to 10 mol % based on the molar amount of the ethylenically unsaturated monomer.
For instance in step b2) the reaction product of step a2) is present in an amount from 0.01 to 10 mol % based on the molar amount of the ethylenically unsaturated monomer.
Typically the average weight molecular weight MW of the star polymer or copolymer is from 1000 to 300 000, preferably from 3000 bis 100000.
The polydispersity index of the resulting comb or star copolymer is typically between 1.1 and 3.0.
Because the polymerization of step b) is a “quasi living” polymerization, it can be started and stopped practically at will. Furthermore, the polymer product retains the functional alkoxyamine group allowing a continuation of the polymerization in a living matter. Thus, in one embodiment of this invention, once the first monomer is consumed in the initial radical polymerizing step a second monomer can then be added to form a second block on the growing polymer chain in a second polymerization step. Therefore it is possible to carry out additional polymerizations with the same or different monomer(s) to prepare multi-block copolymers.
Furthermore, since this is a “quasi living” radical polymerization, blocks can be prepared in essentially any order. One is not necessarily restricted to preparing block copolymers where the sequential polymerizing steps must flow from the least stabilized polymer intermediate to the most stabilized polymer intermediate, such as is the case in ionic polymerization. Thus it is possible to prepare a multi-block copolymer in which a polyacrylonitrile or a poly(meth)-acrylate block is prepared first, then a styrene or butadiene block is attached thereto, and so on.
Random copolymers and tapered copolymer structures can be synthesized as well by using a mixture of monomers or adding a second monomer before the first one is completely consumed.
A further aspect of the invention is a star polymer or copolymer obtainable in a method as described above.
Yet another aspect of the invention is the use of a star polymer or copolymer obtainable according to the method described above as crosslinking agent, ionomer, emulsifier, adhesive, surface modifier, surfactant or compatibilizer in thermoplastic, elastic or thermosetting polymers or as plastic material for extrusion or injection molding for shaping parts.
The following examples illustrate the invention.
Solvents and monomers are distilled over a Vigreux column under argon atmosphere or under vacuum, shortly before being used.
To remove oxygen all polymerization reaction mixtures are flushed before polymerization with argon and evacuated under vacuum applying a freeze-thaw cycle. The reaction mixtures are then polymerized under argon atmosphere.
At the start of the polymerization reaction, all starting materials are homogeneously dissolved.
Conversion is determined by removing unreacted monomers from the polymer by precipitation in methanol and/or by drying in vacuo (0.002 torr) at least 60 minutes, weighing the remaining polymer and subtract the weight of the initiator.
Characterization of the polymers is carried out by GPC (Gel Permeation Chromatography). GPC: Is performed using RHEOS 4000 of FLUX INSTRUMENTS. Tetrahydrofurane (THF) is used as a solvent and is pumped at 1 ml/min. Two chromatography columns are put in series: type PIgel 5 μm mixed-C of POLYMER INSTRUMENTS, Shropshire, UK. Measurements are performed at 40° C. The columns are calibrated with low polydispersity polystyrenes having Mn from 200 to 2 000 000 Dalton. Detection is carried out using a RI-Detector ERC-7515A of ERCATECH AG at 30° C.
1H-NMR is performed using a BRUKER AVANCE 200.
Compound 103
has been prepared according to WO 02/48109.
Preparation of a Star Polymer with Polystyrene Side Arms
Two step reaction:
1st step: Synthesis of multifunctional initiator compound
2nd step: CFRP with styrene to prepare a star polymer
1st step: Reaction Between Tris(2-aminomethyl)amine and Compound 103
In a dry, Argon-purged Schlenk tube equipped with a rubber septum, a magnetic stir bar and an Argon inlet, 0.618 g (0.00423 mol) tris(2-aminomethyl)amine and 5,502 g (0,01269 mol) compound 103 are dissolved in 15 ml dry toluene. The solution is heated at 90° C. for 9 h. After cooling down at room temperature the solvent is removed in vacuo and the resulting compound is dried overnight in vacuo at 50° C. until weight constant.
The multifunctional initiator compound A is obtained as slight yellow solid in quantitative yield
1H-NMR: no further epoxy-groups in the spectra confirms the complete reaction of the epoxy-functionalized NOR with the triamine.
2nd step: Reinitiation of Multifunctional Initiator Compound A with Styrene
In a dry, Argon-purged Schienk tube equipped with a rubber septum, a magnetic stir bar and an Argon inlet, 2,5 g compound A is dissolved in 90 g (0,864 mol) styrene. The solution is heated at 130° C. for 6 h. After cooling down at room temperature the residual monomer (styrene) is removed in vacuo and the resulting star polymer is dried overnight in vacuo at 50° C. until constant weight.
The star polymer is obtained as white solid with a conversion of 55%.
| Number | Date | Country | Kind |
|---|---|---|---|
| 05102621.9 | Apr 2005 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/061045 | 3/27/2006 | WO | 00 | 8/5/2009 |
