WO2002030996A2

WO2002030996A2 - Multi-functional initiators for atom transfer radical polymerization

Info

Publication number: WO2002030996A2
Application number: PCT/US2001/032141
Authority: WO
Inventors: Kevin C. Olson; James B. O'dwyer; Simion Coca
Original assignee: Ppg Industries Ohio, Inc.
Priority date: 2000-10-13
Filing date: 2001-10-12
Publication date: 2002-04-18
Also published as: WO2002030996A3; AU2002215351A1

Abstract

The present invention is directed to a controlled radical polymerization process in which novel (co)polymers are prepared using alkylene bis-(dialkyl 2-halomalonate) initiators, such as a methylene bis-(diethyl 2-bromomalonate). The present invention is also directed to novel (co)polymer products of the process.

Description

Multi-Functional Initiators for Atom Transfer Radical Polymerization FIELD OF THE INVENTION

The present invention relates to a novel polymer composition prepared in a controlled radical polymerization process as well as to a novel controlled radical polymerization process.

BACKGROUND OF THE INVENTION

A wide variety of radically polymerizable monomers, such as methacrylate and acrylate monomers, are commercially available and can confer to a polymer or (co)polymer (hereinafter, collectively referred to as (co) polymers) produced therefrom a wide range of properties including, for example, hydrophilic and hydrophobic properties or the ability to interact with crosslinkers or to self crosslink. The use of conventional, i.e., non-living or free-radical polymerization, methods to synthesize (co)polymers provides little control over molecular weight, molecular weight distribution and, in particular, (co)polymer chain structure. United States Patent Nos. 5,807,937; 5,789,487; and 5,763,548, and

International Patent Publication Nos. WO 98/40415; WO 98/01480; WO 97/18247 and WO 96/30421 describe a radical polymerization process referred to as atom transfer radical polymerization (ATRP). The ATRP process is described as being a living radical polymerization that results in the formation of (co)polymers having predictable molecular weight and molecular weight distribution. The ATRP process also is described as providing highly uniform products having controlled structure, i.e., controllable topology, composition, etc. The '937 and '548 patents also describe (co)polymers prepared by ATRP, which are useful in a wide variety of applications including, for example, dispersants and surfactants. A number of initiators and macroinitiator systems are known to support ATRP polymerization. These initiators are described, for example, in U.S. Patent Nos. 5,807,937 and 5,986,015. U.S. Patent No. 5,807,937 discloses a number of initiators, including halide groups attached to a primary carbon. Halides attached to primary carbons are known as efficient initiators in ATRP processes. U. S. Patent No. 5,986,015 discloses (co)polymer macroinitiators prepared from vinyl chloride and another monomer, and their use in preparing graft (co)polymers with low polydispersity.

It is desirable to have multiple initiation sites on an initiator in order to create unique (co)polymer structures. Such (co)polymers have a variety of practical applications, including a resin component of a film-forming coating composition. These unique polymers also will find use in the health care or cosmetics industries, for instance, as materials for bioengineering. (Co)polymers of low polydispersity (Mn/Mw) are also desirable not only for their structural regularity and related usefulness in producing defined block and multiblock (co)polymer structures, but for their unique physical characteristics.

It is therefore desired to have a polyfunctional (two or more initiator sites) ATRP initiator where each initiator site has the same or very similar initiation efficiency (Kj) as the other initiator sites. It is also desirable that the initiators can be easily prepared from inexpensive and readily available compounds. SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a novel (co)polymer that is prepared by a controlled radical polymerization process using an initiator including two initiation sites having the same or very similar initiation efficiencies (K,-), so that a (co)polymer prepared therefrom exhibits low polydispersity, i.e., a Mn/Mw of less than about two.

The (co)polymer is prepared by an atom transfer radical polymerization process that is conducted in the presence of an initiator having a group of the structure:

in which R is a divalent organic linking group, preferably methylene and X and X' are independently the same or different halide groups. The initiator is preferably defined by the structure:

in which R, X and X' are defined as above and R_{l s} R₂, R₃ and R are independently Cι-2₀ alkyl, C1.2₀ substituted alkyl, C_2-2o alkenyl, C _-8 cycloalkyl or aryl. The initiator is most typically methylene bis-(diethyl 2-bromomalonatediethyl 2-bromomalonate).

The present invention is also directed to a controlled radical polymerization process that utilizes the above-described high efficiency initiators to produce novel (co)polymeric compositions having low polydispersity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Other than in the operating examples, or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, etc., used in the specification and claims are to be understood as modified in all instances by the term "about."

As described above, the present invention is directed to a novel controlled radical polymerization process. The process uses a class of compounds as initiators that heretofore have not been used as initiators for controlled radical polymerization processes. An example of a suitable initiator is methylene bis-(diethyl 2- bromomalonatediethyl 2-bromomalonate).

The use of the novel controlled radical polymerization process of the present invention permits the production of novel (co)polymers, preferably linear (co)polymers with exceptionally low polydispersity. The (co)polymer of the present invention is prepared by controlled radical polymerization. As used herein and in the claims, the term "controlled radical polymerization" and related terms, e.g., "living radical polymerization" refer to those methods of radical polymerization that provide control over the molecular weight, (co)polymer chain architecture and polydispersity of the resulting (co)polymer. A controlled or living radical polymerization is also described as a chain-growth polymerization that propagates with essentially no chain transfer and essentially no chain termination. The number of living (co)polymer chains formed during a controlled radical polymerization is often nearly equal to the number of initiators present at the beginning of the reaction. Each living (co)polymer chain typically contains a residue of the initiator at what is commonly referred to as its tail, and a residue of the radically transferable group at what is commonly referred to as its head. Preferably the (co)polymers are linear.

In an embodiment of the present invention, the (co)polymer is prepared by atom transfer radical polymerization (ATRP). The ATRP process comprises: polymerizing one or more radically polymerizable monomers in the presence of a specific initiation system; forming a (co)polymer; and isolating the formed (co)polymer. In the present invention, the initiation system comprises: a monomeric initiator having multiple radically transferable atoms or groups; a transition metal compound, i.e., a catalyst, which participates in a reversible redox cycle with the initiator; and preferably a ligand, which coordinates with the transition metal compound. The ATRP process is described in further detail in International Patent Publication WO 98/40415 and United States Patent Nos. 5,807,937; 5,763,548; and 5,789,487. Catalysts that may be used in the ATRP preparation of the (co)polymer of the present invention include any transition metal compound that can participate in a redox cycle with the initiator and the growing (co)polymer chain. It is preferred that the transition metal compound not form direct metal bonds with the polymer chain. Transition metal catalysts useful in the present invention may be represented by the following general formula (I), (I) TMⁿ⁺X_n wherein TM is the transition metal, n is the formal charge on the transition metal having a value of from 0 to 7, and X is a counterion or covalently bonded component. Examples of the transition metal (TM) include, but are not limited to, Cu, Fe, Au, Ag, Hg, Pd, Pt, Co, Mn, Ru, Mo, Nb and Zn. Examples of X include, but are not limited to, halide, hydroxy, oxygen, Ci-C_δ-alkoxy, cyano, cyanato, thiocyanato and azido. A preferred transition metal is Cu(I) and X is preferably halide, e.g., chloride. Accordingly, a preferred class of transition metal catalysts are the copper halides, e.g., Cu(I)Cl. It is also preferred that the transition metal catalyst contain a small amount, e.g., 1 mole percent, of a redox conjugate, for example, Cu(II)Cl₂ when Cu(I)Cl is used. Additional catalysts useful in preparing the (co)polymer are described in United States Patent No. 5,807,937 at column 18, lines 29 through 56. Redox conjugates are described in further detail in United States Patent No. 5,807,937 at column 11, line 1 through column 13, line 38. Ligands that may be used in the ATRP preparation of the (co)polymer include, but are not limited to, compounds having one or more nitrogen, oxygen, phosphorus and/or sulfur atoms, which can coordinate to the transition metal catalyst compound, e.g., through sigma and/or pi bonds. Classes of useful ligands, include but are not limited to, unsubstituted and substituted pyridines and bipyridines; porphyrins; cryptands; crown ethers; e.g., 18-crown-6; polyamines, e.g., ethylenediamine; glycols, e.g., alkylene glycols, such as ethylene glycol; carbon monoxide; and coordinating monomers, e.g., styrene, acrylonitrile and hydroxyalkyl (meth)acrylates. As used herein and in the claims, the term "(meth)acrylate" and similar terms refer to acrylates, methacrylates, and mixtures of acrylates and methacrylates. A preferred class of ligands are the substituted bipyridines, e.g., 4,4'-dialkyl-bipyridyls. Additional ligands that may be used in preparing the polymer are described in United States Patent No. 5,807,937 at column 18, line 57 through column 21, line 43.

The initiator includes two halide group-containing malonyl initiation sites that are typically connected by aliphatic carbons. The connecting aliphatic carbons may include aromatic residues so long as the initiation sites are "isolated." Typically the connecting carbons are aliphatic (free from aromatic moieties). By "isolated" it is meant that the Kj and K_p for each initiation site is not affected substantially by the initiation and propagation of polymerization on a second initiation site on the same initiator. The initiation sites are also preferably symmetrical. By "symmetrical" it is meant that the K,- (initiation constant) for each initiation site, and typically the K_p (propagation constant) is substantially the same. The initiator typically has a group of the structure of formula II:

in which R is a divalent organic linking group and X and X' are independently the same or different halide groups, preferably both halide groups are bromide. The initiator is preferably defined by the general formula III:

in which R, X and X' are defined as above and Ri, R₂, R₃ and R4 are independently the same or different and can be hydrogen, straight or branched alkyl of 1 to 20 carbon atoms (preferably from 2 to 6 carbon atoms, more preferably from 2 to 4 carbon atoms), unsaturated straight or branched alkenyl or alkynyl of 2 to 10 carbon atoms (preferably from 2 to 6 carbon atoms, more preferably from 2 to 4 carbon atoms), C - C₈ cycloalkyl, aryl or heterocyclyl.

The term "aryl" refers to phenyl, naphthyl, phenanthryl, phenalenyl, anthracenyl, triphenylenyl, fluoranthenyl, pyrenyl, pentacenyl, chrysenyl, naphthacenyl, hexaphenyl, picenyl and perylenyl (preferably phenyl and naphthyl), in which each hydrogen atom maybe replaced with alkyl of from 1 to 20 carbon atoms (preferably from 1 to 6 carbon atoms and more preferably methyl), alkyl of from 1 to 20 carbon atoms (preferably from 1 to 6 carbon atoms and more preferably methyl) in which each of the hydrogen atoms is independently replaced by a halide (preferably a fluoride or a chloride), alkenyl of from 2 to 20 carbon atoms, alkynyl of from 1 to 20 carbon atoms, alkoxy of from 1 to 6 carbon atoms, alkylthio of from 1 to 6 carbon atoms, C -C₈ cycloalkyl, phenyl, halogen, NH₂, Ci -C₆ -alkylamino, Ci -C₆ - dialkylamino, and phenyl which may be substituted with from 1 to 5 halogen atoms and/or Ci -C₄ alkyl groups. The term "heterocyclyl" refers to pyridyl, furyl, pyrrolyl, thienyl, imidazolyl, pyrazolyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyranyl, indolyl, isoindolyl, indazolyl, benzofuryl, isobenzofuryl, benzothienyl, isobenzothienyl, chromenyl, xanthenyl, purinyl, pteridinyl, quinolyl, isoquinolyl, phthalazinyl, quinazolinyl, quinoxalinyl, naphthyridinyl, phenoxathiinyl, carbazolyl, cinnolinyl, phenanthridinyl, acridinyl, 1,10-phenanthrolinyl, phenazinyl, phenoxazinyl, phenothiazinyl, oxazolyl, thiazolyl, isoxazolyl, isothiazolyl, and hydrogenated forms thereof known to those in the art. Preferred heterocyclyl groups include pyridyl, furyl, pyrrolyl, thienyl, imidazolyl, pyrazolyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyranyl and indolyl, the most preferred heterocyclyl group being pyridyl. Ri, R₂, R₃ and R_₄ are preferably lower alkyl, from 1 to 6 carbon atoms, and most preferably lower alkyl from 1 to 4 carbon atoms.

The divalent organic linking group R can be a linear, branched or cyclic, primarily aliphatic group having a theoretically unlimited molecular weight and degree of branching and cyclization. The linking group may contain one or more aromatic moieties, so long as the isolation of the two initiation sites is not affected by the presence of the aromatic moieties. Depending upon the method by which the initiator is formed, the linking group may contain one or more hetero atoms, for example, and without limitation, N, S, O, P or Si, or groups comprising these atoms, such as, without limitation, ester, ether, urethane, urea, amide, silyl, siloxyl, sulfonate and phosphate ester groups. Preferably, the divalent linking group R is methylene.

An example of the initiator of the present invention is an alkylene bis-(dialkyl 2-halomalonate) such as methylene bis-(diethyl 2-bromomalonate). This specific initiator is a very efficient di-functional initiator that produces symmetrical (co)polymers with low polydispersity. As an example, the initiator methylene bis- (diethyl 2-bromomalonate) is easily and very inexpensively synthesized by reacting diethylmalonate with formaldehyde in a 2:1 molar ratio, in the presence of triethylamine followed by bromination.

In the present invention any radically polymerizable alkene containing a polar group can serve as a monomer for polymerization. The preferred monomers are ethylenically unsaturated monomers include those of general formula IV:

wherein R₅ and R₆ are i

from the group consisting of H, halogen, CN, CF₃, straight or branched alkyl of 1 to 20 carbon atoms (preferably from

1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms), aryl, unsaturated straight or branched alkenyl or alkynyl of 2 to 10 carbon atoms (preferably from 2 to 6 carbon atoms, more preferably from 2 to 4 carbon atoms), unsaturated straight or branched alkenyl of 2 to 6 carbon atoms (preferably vinyl) substituted (preferably at the α-position) with a halogen (preferably chlorine), C₃-C₈ cycloalkyl, heterocyclyl, phenyl which may optionally have from 1-5 substituents on the phenyl ring, C(=Y)R , C(=Y)NR,o Ru, YCR,₀ Ru R.₂ and YC(=Y)R₁₂, where Y may be NR₁₂ or O (preferably O), R₉ is alkyl of from 1 to 20 carbon atoms, alkoxy of from 1 to 20 carbon atoms, aryloxy or heterocyclyloxy, Rio and Ru are independently H or alkyl of from 1 to 20 carbon atoms, or R_]0 and Rn may be joined together to form an alkylene group of from 2 to 5 carbon atoms, thus forming a 3- to 6-membered ring, and R₁₂ is H, straight or branched Ci -C₂₀, alkyl and aryl; and R₇ is selected from the group consisting of H, halogen (preferably fluorine or chlorine), -C₆ (preferably Ci) alkyl, CN, COOR12 (where R_!2 is H, an alkali metal, or a -C₆ alkyl group) or aryl; or R and R₆ may be joined to form a group of the formula (CH₂)_n, (which may be substituted with from 1 to 2n' halogen atoms or Ci -C₄ alkyl groups) or C(=O)— Y— C(=O), where n' is from 2 to 6 (preferably 3 or 4) and Y is as defined above; and R₈ is the same as R or R_ό or optionally R₈ is a CN group; at least two of R₅, R₆, and R₇ are H or halogen.

Specific examples of vinyl monomers that may be polymerized by the ATRP process include vinyl monomers, allylic monomers, olefins (meth)acrylic acid, (meth)acrylates, (meth)acrylamide, N- and N,N-disubstituted (meth)acrylamides, vinyl aromatic monomers, vinyl halides, vinyl esters of carboxylic acids and mixtures thereof. More specific examples of suitable monomers include, without limitation, C₁-C2₀ alkyl (meth)acrylates (including linear or branched alkyls and cycloalkyls) which include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, 3,3,5- trimethylcyclohexyl (meth)acrylate and isocane (meth)acrylate; oxirane functional (meth)acrylates which include, but are not limited to, glycidyl (meth)acrylate, 3,4- epoxycyclohexylmethyl(meth)acrylate, and 2-(3,4-epoxycyclohexyl) ethyl(meth)acrylate; hydroxy alkyl (meth)acrylates having from 2 to 4 carbon atoms in the alkyl group which include, but are not limited to, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and hydroxybutyl (meth)acrylate. The residues may each independently be residues of monomers having more than one (meth)acryloyl group, such as (meth)acrylic anhydride, diethyleneglycol bis(meth)acrylate, 4,4'- isopropylidenediphenol bis(meth)acrylate (Bisphenol A di(meth)acrylate), alkoxylated 4,4'-isopropylidenediphenol bis(meth)acrylate, trimethylolpropane tris(meth)acrylate and alkoxylated trimethylolpropane tris(meth)acrylate. In the context of the present application, the terms "alkyl", "alkenyl" and "alkynyl" refer to straight-chain or branched groups. Furthermore, in the present application, "aryl" refers to phenyl, naphthyl, phenanthryl, phenalenyl, anthracenyl, triphenylenyl, fluoranthenyl, pyrenyl, pentacenyl, chrysenyl, naphthacenyl, hexaphenyl, picenyl and perylenyl (preferably phenyl and naphthyl), in which each hydrogen atom may be replaced with alkyl of from 1 to 20 carbon atoms (preferably from 1 to 6 carbon atoms and more preferably methyl), alkyl of from 1 to 20 carbon atoms (preferably from 1 to 6 carbon atoms and more preferably methyl) in which each of the hydrogen atoms is independently replaced by a halide (preferably a fluoride or a chloride), alkenyl of from 2 to 20 carbon atoms, alkynyl of from 1 to 20 carbon atoms, alkoxy of from 1 to 6 carbon atoms, alkylthio of from 1 to 6 carbon atoms, C₃-C₈ cycloalkyl, phenyl, halogen, NH₂, Ci -C₆ -alkylamino, d -C₆ - dialkylamino, and phenyl which may be substituted with from 1 to 5 halogen atoms and or -C₄ alkyl groups. (This definition of "aryl" also applies to the aryl groups in "aryloxy" and "aralkyl.") Thus, phenyl may be substituted from 1 to 5 times and naphthyl may be substituted from 1 to 7 times (preferably any aryl group, if substituted, is substituted from 1 to 3 times) with one of the above substituents. More preferably, "aryl" refers to phenyl, naphthyl, phenyl substituted from 1 to 5 times with fluorine or chlorine, and phenyl substituted from 1 to 3 times with a substituent selected from the group consisting of alkyl of from 1 to 6 carbon atoms, alkoxy of from 1 to 4 carbon atoms and phenyl. Most preferably, "aryl" refers to phenyl and tolyl.

Specific examples of vinyl aromatic monomers that may be used to prepare the (co)polymer include, but are not limited to, styrene, p-chloromethyl styrene, divinyl benzene, vinyl naphthalene and divinyl naphthalene. Vinyl halides that may be used to prepare the graft (co)polymer include, but are not limited to, vinyl chloride, p- chloromethylstyrene, vinyl chloroacetate and vinylidene fluoride. Vinyl esters of carboxylic acids that may be used to prepare the graft (co)polymer include, but are not limited to, vinyl acetate, vinyl butyrate, vinyl 3,4-dimethoxybenzoate and vinyl benzoate. In the context of the present invention, "heterocyclyl" refers to pyridyl, furyl, pyrrolyl, thienyl, imidazolyl, pyrazolyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyranyl, indolyl, isoindolyl, indazolyl, benzo furyl, isobenzofuryl, benzothienyl, isobenzothienyl, chromenyl, xanthenyl, purinyl, pteridinyl, quinolyl, isoquinolyl, phthalazinyl, quinazolinyl, quinoxalinyl, naphthyridinyl, phenoxathiinyl, carbazolyl, cinnolinyl, phenanthridinyl, acridinyl, 1,10-phenanthrolinyl, phenazinyl, phenoxazinyl, phenothiazinyl, oxazolyl, thiazolyl, isoxazolyl, isothiazolyl, and hydrogenated forms thereof known to those in the art. Preferred heterocyclyl groups include pyridyl, furyl, pyrrolyl, thienyl, imidazolyl, pyrazolyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyranyl and indolyl, the most preferred heterocyclyl group being pyridyl. Accordingly, suitable vinyl heterocycles to be used as a monomer in the present invention include 2-vinyl pyridine, 4-vinyl pyridine, 2-vinyl pyrrole, 3-vinyl pyrrole, 2-vinyl oxazole, 4-vinyl oxazole, 5-vinyl oxazole, 2-vinyl thiazole, 4-vinyl thiazole, 5-vinyl thiazole, 2-vinyl imidazole, 4-vinyl imidazole, 3-vinyl pyrazole, 4-vinyl pyrazole, 3-vinyl pyridazine, 4-vinyl pyridazine, 3-vinyl isoxazole, 3-vinyl isothiazoles, 2-vinyl pyrimidine, 4-vinyl pyrimidine, 5-vinyl pyrimidine, and any vinyl pyrazine, the most preferred being 2-vinyl pyridine. The vinyl heterocycles mentioned above may bear one or more (preferably 1 or 2) Ci -C₆ alkyl or alkoxy groups, cyano groups, ester groups or halogen atoms, either on the vinyl group or the heterocyclyl group, but preferably on the heterocyclyl group. Further, those vinyl heterocycles which, when unsubstituted, contain an N— H group may be protected at that position with a conventional blocking or protecting group, such as a -C₆ alkyl group, a tris- Ci -C<₅ alkylsilyl group, an acyl group of the formula Rι₃ CO (where Rι₃ is alkyl of from 1 to 20 carbon atoms, in which each of the hydrogen atoms may be independently replaced by halide, preferably fluoride or chloride), alkenyl of from 2 to 20 carbon atoms (preferably vinyl), alkynyl of from 2 to 10 carbon atoms (preferably acetylenyl), phenyl which may be substituted with from 1 to 5 halogen atoms or alkyl groups of from 1 to 4 carbon atoms, or aralkyl (aryl-substituted alkyl, in which the aryl group is phenyl or substituted phenyl and the alkyl group is from 1 to 6 carbon atoms), etc. (This definition of "heterocyclyl" also applies to the heterocyclyl groups in "heterocyclyloxy" and "heterocyclic ring.")

More specifically, preferred monomers include, but are not limited to, styrene, p-chloromethylstyrene, vinyl chloroacetate, acrylate and methacrylate esters of d -C₂o alcohols, isobutene, 2-(2-bromopropionoxy) ethyl acrylate, acrylonitrile, and methacrylonitrile.

As used herein and in the claims, by "allylic monomer(s)" is meant monomers containing substituted and or unsubstituted allylic functionality, i.e., one or more radicals represented by the following general formula V, (V) H₂0=C(Rι₄)-CH₂- wherein R is hydrogen, halogen or a to C alkyl group. Most commonly, Rι is hydrogen or methyl and, consequently, general formula V represents the unsubstituted (meth)allyl radical. Examples of allylic monomers include, but are not limited to, (meth)allyl ethers, such as methyl (meth)allyl ether and (meth)allyl glycidyl ether; allyl esters of carboxylic acids, such as (meth)allyl acetate, (meth)allyl butyrate, (meth)allyl 3,4-dimethoxybenzoate and (meth)allyl benzoate.

Other ethylenically unsaturated radically polymerizable monomers that may be used to prepare the (co)polymer include, but are not limited to, cyclic anhydrides, e.g., maleic anhydride, l-cyclopentene-l,2-dicarboxylic anhydride and itaconic anhydride; esters of acids that are unsaturated but do not have α,β-ethylenic unsaturation, e.g., methyl ester of undecylenic acid; diesters of ethylenically unsaturated dibasic acids, e.g., di(C)-C alkyl)ethyl maleates; maleimide and N-substituted maleimides. In one embodiment of the present invention, the monomer includes a hydrophobic residue of a monomer selected from an oxirane functional monomer reacted with a carboxylic acid selected from the group consisting of aromatic carboxylic acids, polycyclic aromatic carboxylic acids, aliphatic carboxylic acids having from 6 to 20 carbon atoms and mixtures thereof; C₆-C2₀ alkyl (meth)acrylates, e.g., including those as previously recited herein; aromatic (meth)acrylates, e.g., phenyl (meth)acrylate, p-nitrophenyl (meth)acrylate and benzyl (meth)acrylate; polycyclicaromatic (meth)acrylates, e.g., 2-naphthyl (meth)acrylate; vinyl esters of carboxylic acids, e.g., hexanoic acid vinyl ester and decanoic acid vinyl ester; N,N- di(Cι-C₈ alkyl) (meth)acrylamides; maleimide; N-(Cι-C₂o alkyl) maleimides; N-(C₃- C₈ cycloalkyl) maleimides; N-(aryl) maleimides; and mixtures thereof. Examples of N-substituted maleimides include, but are not limited to, N-(Cι-C₂o linear or branched alkyl) maleimides, e.g., N-methyl maleimide, N-tertiary-butyl maleimide, N-octyl maleimide and N-icosane maleimide; N~(C₃-C₈ cycloalkyl) maleimides, e.g., N- cyclohexyl maleimide; and N-(aryl) maleimides, e.g., N-phenyl maleimide, N-(Cι-C₉ linear or branched alkyl substituted phenyl) maleimide, N-benzyl maleimide and N- (Cι-C linear or branched alkyl substituted benzyl) maleimide. The oxirane functional monomer or its residue that is reacted with a carboxylic acid, may be selected from, for example, glycidyl (meth)acrylate, 3,4- epoxycyclohexylmethyl(meth)acrylate, 2-(3,4-epoxycyclohexyl) ethyl(meth)acrylate, allyl glycidyl ether and mixtures thereof. Examples of carboxylic acids that may be reacted with the oxirane functional monomer or its residue include, but are not limited to, para-nitrobenzoic acid, hexanoic acid, 2-ethyl hexanoic acid, decanoic acid, undecanoic acid and mixtures thereof.

The monomer containing at least one polar group may be present in an amount of 5 to 100 wt % by weight based on the total amount of monomers. A preferred amount of the monomer containing at least one polar group is 10 to 100 wt %; the most preferred amount is 20 to 100 wt % based on the total amount of monomers. This is particularly important in the case of acrylonitrile because an amount of at least 20 wt % assures solvent resistance properties of the resulting (co)polymer A.

In the ATRP preparation of the (co)polymer of the present invention, the amounts and relative proportions of the initiator, the transition metal compound and the ligand are those for which ATRP is most effectively performed. The amount of initiator used can vary widely and is typically present in the reaction medium in a concentration of from 10^"4 moles / liter (M) to 3 M, for example, from 10^"3 M to 10^"1 M. As the molecular weight of the polymer product can be directly related to the relative concentrations of initiator and monomer(s), the molar ratio of initiator to monomer is an important factor in polymer preparation. The molar ratio of initiator to monomer is typically within the range of 10^"4 : 1 to 0.5 : 1, for example, 10^"3 : 1 to 5 x 10^"2 : 1.

In preparing the (co)polymer by ATRP methods, the molar ratio of transition metal compound to initiator is typically in the range of 10^"4 : 1 to 10 : 1, for example, 0.1 : 1 to 5 : 1. The molar ratio of ligand to transition metal compound is typically within the range of 0.1 : 1 to 100 : 1, for example, 0.2 : 1 to 10 : 1.

The (co)polymer may be prepared in the absence of solvent, i.e., by means of a bulk polymerization process. Generally, the (co)ρolymer is prepared in the presence of a solvent, typically an organic solvent. Classes of useful organic solvents include, but are not limited to, esters of carboxylic acids, ethers, cyclic ethers, C₅-C₁₀ alkanes, C₅-C₈ cycloalkanes, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, amides, nitriles, sulfoxides, sulfones and mixtures thereof. Supercritical solvents, such as CO₂, C]-C alkanes and fluorocarbons, may also be employed. A preferred class of solvents are the aromatic hydrocarbon solvents, particularly preferred examples of which are xylene, toluene, and mixed aromatic solvents such as those commercially available from Exxon Chemical America under the trademark SOLVESSO. Additional solvents are described in further detail in United States Patent No. 5,807,937 at column 21, line 44 through column 22, line 54.

The ATRP preparation of the (co)polymer typically is conducted at a reaction temperature within the range of 25°C to 140°C, preferably from 50°C to 100°C, and a pressure within the range of 1 to 100 atmospheres, usually at ambient pressure. The atom transfer radical polymerization is typically completed in less than 24 hours, e.g., between 1 and 8 hours.

The ATRP transition metal catalyst and its associated ligand typically are separated or removed from the (co)polymer product prior to its use. Removal of the ATRP catalyst may be achieved using known methods, including, for example, adding a catalyst binding agent to the mixture of the (co)polymer, solvent, and catalyst, followed by filtering. Examples of suitable catalyst binding agents include, for example, alumina, silica, clay or a combination thereof. A mixture of the polymer, solvent, and ATRP catalyst may be passed through a bed of catalyst binding agent. Alternatively, the ATRP catalyst may be oxidized in situ, the oxidized residue of the catalyst being retained in the (co)polymer.

The (co)polymers of the present invention include a variety of structures, depending upon the structure of the initiator and on the choice of monomers used in propagating the (co)polymer, the reaction conditions and the method of termination of the polymerization process. The (co)polymers of the present invention are preferably linear.

The initiators may include active hydrogen-containing groups to permit crosslinking of the initiator by known crosslinking methods. The initiator may include other functionality, such as one or more ionic group or groups that can be converted into ionic groups, such as quaternary amine or sulfonium groups. An ionic group-containing polymer prepared in such a manner can be useful as a component of an electrodepositable film-forming composition for use in preparing a coating layer on an electroconductive substrate. The initiator may further contain an active group that permits grafting of other groups to the (co)polymer, such as (co)polymer chains that cannot be prepared by a controlled radical polymerization process. An example of such a chain is a polyoxyalkylene chain, which may be useful in solubilizing the (co)polymer, depending upon the intended use for the (co)polymer.

The choice of monomers used in preparing the (co)polymer also is an important factor in determining the structure of the (co)polymer. A homopolymer will be produced if only one monomer is used. (Co)polymers may be mixed (co)polymers produced by chain propagation in the presence of two monomers. Block (co)polymers can be produced by chain propagation with a sequence of different monomers. The use of hydrophilic monomers, i.e., a poly(alkylene glycol) (meth)acrylate, or hydrophobic monomers, i.e., an alkyl (meth)acrylate, will dictate the hydrophobicity and hydrophilicity of defined portions of the (co)polymer structure. The use of active hydrogen-containing monomers (i.e., a hydroxyalkyl (meth)acrylate, a (meth)acrylamide or (meth)acrylic acid) will dictate the reactivity of portions of the (co)polymer to crosslinkers and/or other co-reactive group-containing materials. As described above, the (co)polymer may have nonionic moieties, ionic moieties and combinations thereof, hi one embodiment of the present invention to introduce hydrophilic segments into the (co)polymer, the monomer can be selected from poly( alkylene glycol) (meth)acrylates; Cι-C alkoxy poly(alkylene glycol) (meth)acrylates; hydroxyalkyl (meth)acrylates having from 2 to 4 carbon atoms in the alkyl group; N-(hydroxy Cι-C alkyl) (meth)acrylamides (e.g., N-hydroxymethyl (meth)acrylamide and N-(2-hydroxyethyl) (meth)acrylamide); N,N-di-(hydroxy Cι-C₄ alkyl) (meth)acrylamides (e.g., N,N-di(2-hydroxyethyl) (meth)acrylamide); carboxylic acid functional monomers; salts of carboxylic acid functional monomers; amine functional monomers; salts of amine functional monomers; and mixtures thereof.

Poly(alkylene glycol) (meth)acrylates and Cj-C₄ alkoxy poly(alkylene glycol) (meth)acrylates are prepared by known methods. For example, (meth)acrylic acid or hydroxyalkyl (meth)acrylate, e.g., 2-hydroxyethyl (meth)acrylate, may be reacted with one or more alkylene oxides, e.g., ethylene oxide, propylene oxide and butylene oxide. Alternatively, an alkyl (meth)acrylate may be transesterified with a Cι-C alkoxy poly( alkylene glycol), e.g., methoxy poly(ethylene glycol). Examples of poly(alkylene glycol) (meth)acrylates and Cι-C₄ alkoxy poly(alkylene glycol) (meth)acrylates include, poly(ethylene glycol) (meth)acrylate and methoxy poly(ethylene glycol) (meth)acrylate, the poly(ethylene glycol) moiety of each having a molecular weight of from 100 to 800. An example of a commercially available

C alkoxy poly(alkylene glycol) (meth)acrylate is methoxy poly(ethylene glycol) 550 methacrylate monomer from Sartomer Company, Inc.

Examples of carboxylic acid functional monomers include, but are not limited to, (meth)acrylic acid, maleic acid, fumaric acid and undecylenic acid. The monomer may be a residue of a precursor of a carboxylic acid functional monomer that is converted to a carboxylic acid residue after completion of the controlled radical polymerization, e.g., maleic anhydride, di(Cι-C alkyl) maleates and Cι-C alkyl (meth)acrylates. For example, residues of maleic anhydride can be converted to diacid residues, ester/acid residues or amide/acid residues by art-recognized reactions with water, alcohols or primary amines, respectively. Residues of Cι-C alkyl (meth)acrylates, such as t-butyl methacrylate, can be converted to (meth)acrylic acid residues by art-recognized ester hydrolyzation methods, which typically involve the concurrent removal of an alcohol, such as t-butanol by vacuum distillation. Salts of carboxylic acid functional monomers include, for example, salts of (meth)acrylic acid and primary, secondary or tertiary amines, such as, butyl amine, dimethyl amine and triethyl amine.

Amine functional monomers include, for example, amino(C2-C alkyl) (meth)acrylates, e.g., 2-aminoethyl (meth)acrylate, 3-aminopropyl (meth)acrylate and 4-aminobutyl (meth)acrylate; N-(CpC₄ alkyl)amino(C₂-C₄ alkyl) (meth)acrylates, e.g., N-methyl-2-aminoethyl (meth)acrylate; and N,N-di(Cι-C₄ alkyl)amino(C2-C alkyl) (meth)acrylates, e.g., N,N-dimethyl-2-aminoethyl (meth)acrylate. The monomer may also comprise residues of salts of amine functional monomers, e.g., salts of those amine functional monomers as recited previously herein. Salts of the amine functional monomer residues may be formed by mixing a carboxylic acid, e.g., lactic acid, with the (co)polymer after completion of controlled radical polymerization. In one embodiment of the present invention, the (co)polymer contains a segment that includes carboxylic acid functional monomers selected from (meth)acrylic acid, maleic anhydride, maleic acid, di(Cι-C₄ alkyl) maleates, and mixtures thereof. In a still further embodiment of the present invention, the polymer segment is a residue of amine functional monomers selected from amino(C₂-C alkyl) (meth)acrylates, N-(Cι-C₄ alkyl)amino(C₂-C₄ alkyl) (meth)acrylates, N,N-di(Cι-C alkyl)amino(C₂-C alkyl) (meth)acrylates and mixtures thereof.

The (co)polymer also may contain a segment that contains cationic moieties selected from ammonium, sulphonium and phosphonium. Ammonium, sulphonium and phosphonium moieties may be introduced into the graft copolymer by means known to the skilled artisan. For example, when the (co)polymer contains a residue ofN,N-dimethyl-2-aminoethyl (meth)acrylate, the N,N-dimethylamino moieties may be converted to ammonium moieties by mixing an acid, e.g., lactic acid, with the (co)polymer. When the segment of the (co)polymer contains residues of oxirane functional monomers, such as glycidyl (meth)acrylate, the oxirane groups may be used to introduce sulphonium or phosphonium moieties into the (co)polymer. Sulphonium moieties may be introduced into the (co)polymer by reaction of the oxirane groups with thiodiethanol in the presence of an acid, such as lactic acid. Reaction of the oxirane groups with a phosphine, e.g., triphenyl phosphine or tributyl phosphine, in the presence of an acid, such as lactic acid, results in the introduction of phosphonium moieties into the (co)polymer.

The (co)polymer can be a block (co)polymer having one or more segments. In a two-segment (co)polymer, the (co)polymer may have the general formula VI:

(VI) φ-(A_p-B_s-X)₂

where each of A and B in general formula VI may represent one or more types of monomer residues, while p and s represent the average total number of A and B residues occurring per block or segment of A residues (A-block or A-segment) and B residues (B-block or B-segment), respectively, and φ is the residue from the initiator and X is a halide. When containing more than one type or species of monomer residue, the A- and B-blocks may each have at least one of random, block, e.g., di- block and tri-block, alternating and gradient architectures. Gradient architecture refers to a sequence of different monomer residues that changes gradually in a systematic and predictable manner along the polymer backbone. For purposes of illustration, an A-block containing 6 residues of methyl methacrylate (MMA) and 6 residues of ethyl methacrylate (EMA), for which p is 12, may have di-block, tetra- block, alternating and gradient architectures as represented in general formulas VII, Vπi, IX and X. vπ

Di-Block Architecture -(MMA-MMA-MMA-MMA-MMA-MMA-EMA-EMA-EMA-EMA-EMA-EMA)- vπi

Tetra-Block Architecture -(MMA-MMA-MMA-EMA-EMA-EMA-MMA-MMA-MMA-EMA-EMA-EMA)-

IX Alternating Architecture

-(MMA-EMA-MMA-EMA-MMA-EMA-MMA-EMA-MMA-EMA-MMA-EMA)-

X Gradient Architecture -(MMA-MMA-MMA-EMA-MMA-MMA-EMA-EMA-MMA-EMA-EMA-EMA)- The B-block may be described in a manner similar to that of the A-block.

The order in which monomer residues occur along the backbone of the (co)polymer typically is determined by the order in which the corresponding monomers are fed into the vessel in which the controlled radical polymerization is conducted. For example, the monomers that are incorporated as residues in the A- block of the graft (co)polymer are generally fed into the reaction vessel prior to those monomers that are incorporated as residues in the B-block.

During formation of the A- and B-blocks, if more than one monomer is fed into the reaction vessel at a time, the relative reactivities of the monomers typically determines the order in which they are incorporated into the living polymer chain. Gradient sequences of monomer residues within the A- and B-blocks can be prepared by controlled radical polymerization, and, in particular, by ATRP methods by (a) varying the ratio of monomers fed to the reaction medium during the course of the polymerization, (b) using a monomer feed containing monomers having different rates of polymerization, or (c) a combination of (a) and (b). (Co)polymers containing gradient architecture are described in further detail in United States Patent No. 5,807,937 at column 29, line 29 through column 31, line 35.

Subscripts p and s represent average numbers of residues occurring in the respective A- and B-blocks. Typically, subscript s has a value of at least 1, and preferably at least 5 for general formula I. Also, subscript s has a value of typically less than 300, preferably less than 100, more preferably less than 50 and most preferably less than 20 for general formula I. The value of subscript s may range between any combination of these values, inclusive of the recited values, e.g., s may be a number from 1 to 100. Subscript p may be 0, or may have a value of at least 1, and preferably at least 5. Subscript p also typically has a value of less than 300, preferably less than 100, more preferably less than 50 and most preferably less than 20. The value of subscript p may range between any combination of these values, inclusive of the recited values, e.g., p may be a number from 0 to 50.

The (co)polymer typically has a number average molecular weight (Mn) of from 400 to 10,000, e.g., from 400 to 5,000 and most preferably from 400 to 1,500, as determined by gel permeation chromatography (GPC) using polystyrene standards. The polydispersity index, i.e., weight average molecular weight (Mw) divided by number average molecular weight (Mn), of graft portion(s) of the (co)polymer typically are less than 2.0, preferably less than 1.8 and most preferably less than 1.5. Symbol φ of general formula V is or is derived from the residue of the initiator used in the preparation of the (co)polymer by controlled radical polymerization, and is free of the radically transferable group of the initiator. When the (co)polymer is initiated in the presence of an initiator as described by general formula III, the symbol φ, more specifically φ-, is the difunctional residue of formula XI:

As a specific example, when the (co)polymer is initiated in the presence of methylene bis-(diethyl 2-bromomalonate), R_{1 ;} R₂, R₃ and R are ethyl.

In the process of the present invention, the radically transferable group is a halide group, preferably a bromide group. For example, in general formula VI, X may be the radically transferable halide groups of an ATRP initiator. The halide residue may be (a) left on the (co)polymer, (b) removed, or (c) chemically converted to another moiety. The radically transferable group may be removed by substitution with a nucleophilic compound, e.g., an alkali metal alkoxylate. Graft-group-terminal halogens can be removed from the (co)polymer by means of a mild dehalogenation reaction. The reaction is typically performed as a post-reaction after the graft (co)polymer has been formed, and in the presence of at least an ATRP catalyst. Preferably, the dehalogenation post-reaction is performed in the presence of both an ATRP catalyst and its associated ligand.

The (co)polymers of the present invention can be used as, without limitation, film-forming compositions, rheology modifiers, pigment or ink dispersants, gel matrices and molding resins. The fields of use of the polymers are varied and include, without limitation, industrial uses, such as in the automotive industry, medical uses, such as in the production of novel films and matrices for use in bioengineering and tissue engineering, pharmaceutical uses, such as in the production of drug delivery matrices and chemical industry uses, such as in the preparation of gels for product separation and purification, and in chemical and biological research, such as in tailored gel matrices for reagent purification.

The present invention is more particularly described in the following Examples, which are intended to be illustrative only, since numerous modifications and variations therein will be apparent to those skilled in the art. Unless otherwise specified, all parts and percentages are by weight.

Example 1: Synthesis of Bis-Malonate Initiator

Example lA: Synthesis of Bis-Malonate Precursor

A monomeric initiator precursor having two radically transferable groups was prepared from the ingredients as enumerated in the following Table A. Table A

Ingredients Parts by weight

Charge 1 Diethyl Malonate 300

Formaldehyde, 37% in Water 80.6

Charge 2

Diethyl Amine 6.8

Charge 3 10% HCl_(aq) 42

Ethyl Acetate 110

Charge 1 was added to a 5 liter, 4-necked flask equipped with a motor driven stainless steel stirrer, water cooled condenser, and a heating mantle and thermometer connected through a temperature feedback control device. With continuous stirring, Charge 2 was added to the flask over a period of 10 minutes, during which time the contents of the flask were observed to exotherm to a temperature of 38°C. With the completion of the addition of Charge 2, the contents of the flask were stirred for an additional 50 minutes during which the contents of the flask continued to exotherm to a temperature of 50°C. At this point, the reaction mixture was heated to and held at 93 °C for seven hours. Upon cooling the contents of the flask to ambient room temperature, Charge 3 was added to the flask. The contents of the flask were transferred to a separatory funnel, the retained organic layer was dried over calcium sulfate and the ethyl acetate was removed by vacuum distillation.

Example IB: Synthesis of Bis-Malonate Initiator

A monomeric initiator having two radically transferable groups (methylene bis-(diethyl 2-bromomalonate)) was prepared from the ingredients as enumerated in the following Table B. Table B

Ingredients Parts by weight

Charge 1

Initiator Precursor of Example 1A 600 Potassium Carbonate (Pulverized) 625

Charge 2

Bromine 625 Charge 3

Deionized Water 2100 Dichloromethane 500

Charge 1 was added to a 5 liter, 4-necked flask equipped with a motor driven glass stirrer, water cooled condenser, addition funnel, and a heating mantle and thermometer connected through a temperature feedback control device. With continuous stirring, Charge 2 was added to the flask over a period of 6.5 hours, during which time the contents of the flask were observed to exotherm to a temperature of 75°C. With the completion of the addition of Charge 2, the contents of the flask were stirred for an additional three hours. Upon complete reaction of the bromine marked by the disappearance of an orange color and the cooling of the contents to ambient room temperature, Charge 3 was added. The contents of the flask were transferred to a separatory funnel, the retained organic layer was dried over calcium sulfate and dichloromethane was removed by vacuum distillation.

Example 2: Synthesis of (co)polymer IBMA/GMA using Difunctional Initiator Methylene Bis-(Diethyl 2-Bromomalonate)

A random (co)polymer was prepared from the ingredients as enumerated in the following Table C. Table C

Ingredients Parts by weight

Charge 1

Aromatic 100¹ 1.74

Copper 0.014

2,2'-Bypyridyl 0.07

Copper(II) bromide 0.05

Methylene bis-(diethyl 2-bromomalonate) (Example 1) 0.98

Isobutyl methacrylate (IBMA) 2.64

Glycidyl methacrylate (GMA) 2.08

¹ AROMATIC 100 is an aromatic solvent blend, commercially available from Exxon.

Charge 1 was heated in a reaction vessel with agitation at 80° C and the reaction mixture was held at this temperature for four hours. The reaction mixture was cooled and filtered. The resultant (co)polymer had a total solid content of 76.5 percent determined at 110°C for one hour. The (co)polymer had number average molecular weight, Mn =2,020 and polydispersity Mw/Mn = 1.3 (determined by gel permeation chromatography using polystyrene as a standard). The IH NMR spectrum is fully consistent with (co)polymer of IBMA and GMA, exhibiting all key absorption of monomers used and the peak arising from initiator.

Calculation of initiator efficiency: Mn(experimental via GPC) = 2,020; Mn(theory) = 2,130; initiator efficiency= Mn(experimental via GPC) / Mn(theory) X100% = 2,020/2,130 X 100% = 94.8%.

The present invention has been described with reference to specific details of particular embodiments thereof. It is not intended that such details be regarded as limitations upon the scope of the invention except insofar as and to the extent that they are included in the accompanying claims.

Claims

We Claim:

1. A (co)polymer prepared by a controlled radical polymerization process that is conducted in the presence of an initiator having a group of the structure:

in which: a) R is a divalent organic linking group; and b) X and X' are independently the same or different halide groups.

2. The (co)polymer of claim 1 in which the initiator has the structure:

in which: a) R is a divalent linking group; b) Ri, R₂, R₃ and R_₄ are independently the same or different selected from the group consiting of hydrogen, straight or branched alkyl of 1 to 20 carbon atoms, unsaturated straight or branched alkenyl or alkynyl of 2 to 10 carbon atoms, C₃-C₈ cycloalkyl, aryl or heterocyclyl; and c) X and X' are independently the same or different halide groups.

3. The (co)polymer of claim 1 in which Ri, R2, R and R4 are independently the same or different lower alkyl from 1 to 4 carbon atoms.

4. The (co)polymer of claim 1 in which R is alkylene.

5. The (co)polymer of claim 1 in which R is methylene.

6. The (co)polymer of claim 1 in which the initiator is methylene bis- (diethyl 2-bromomalonate).

7. The (co)polymer of claim 1 in which the controlled radical polymerization process is an atom transfer radical polymerization process.

8. The (co)polymer of claim 1 having the general formula:

φ-(A_p-B_s-X)₂

in which a) A and B are different ethylenically unsaturated monomers; b) p is an integer from 1 to 300; c) s is an integer from 0 to 300; d) X is a halide; and e) φ is a residue from the initiator and has the general structure:

in which:

R is a divalent linking group; and

Ri, R₂, R and R₄ are independently the same or different sleeted from the group consiting of hydrogen, straight or branched alkyl of 1 to 20 carbon atoms, unsaturated straight or branched alkenyl or alkynyl of 2 to 10 carbon atoms, C -C₈ cycloalkyl, aryl or heterocyclyl.

9. An article prepared from a resinous composition comprising the polymer of claim 1.

10. A method for preparing a (co)polymer comprising the step of (co)polymerizing ethylenically unsaturated monomers in the presence of an initiator under a controlled radical polymerization process, the initiator having the structure:

1 1. The method of claim 10 in which the initiator has the structure:

in which: a) R is a divalent organic linking group; b) Ri, R₂, R and R are independently lower alkyl from 2 to 6 carbon atoms; and o) X and X' are independently halide groups.

12. The method of claim 10 in which the controlled radical polymerization process is an atom transfer radical polymerization process.

13. The method of claim 10 in which the initiator is a methylene bis- (diethyl 2-halomalonate).

14. The method of claim 10 in which the initiator is methylene bis-(diethyl

2-bromomalonate).

15. A polymer prepared by a controlled radical polymerization process that is conducted in the presence of methylene bis-(diethyl 2-bromomalonate) as an initiator.