Arylsulfinate salts in initiator systems for polymeric reactions Number:7,030,169 from the United States Patent and Trademark Office (PTO) owispatent Compositions are provided that that can be used as an initiator system for free radical polymerization reactions. More specifically, the initiator systems include an electron acceptor and an electron donor. The electron donors are arylsulfinate salts having a cation that contains at least one carbon atom and either a positively charged nitrogen atom or a positively charged phosphorus atom. Methods of polymerization are also provided that can be used to prepare polymeric material with the initiator systems. The initiator systems can be thermal initiator systems, photoinitiator systems, or combinations thereof.<H Arylsulfinate, reactions, Arylsulfinate, s, 7030169.html, Patent, pto, 7030169

Title: Arylsulfinate salts in initiator systems for polymeric reactions

Abstract: Compositions are provided that that can be used as an initiator system for free radical polymerization reactions. More specifically, the initiator systems include an electron acceptor and an electron donor. The electron donors are arylsulfinate salts having a cation that contains at least one carbon atom and either a positively charged nitrogen atom or a positively charged phosphorus atom. Methods of polymerization are also provided that can be used to prepare polymeric material with the initiator systems. The initiator systems can be thermal initiator systems, photoinitiator systems, or combinations thereof.

Patent Number: 7,030,169 Issued on 04/18/2006 to Kalgutkar, et al.

Inventors: Kalgutkar; Rajdeep S. (St. Paul, MN); Palazzotto; Michael C. (Woodbury, MN)
Assignee: 3M Innovative Properties Company (St. Paul, MN)

Appl. No.: 672762

Filed: September 26, 2003

Current U.S. Class: 522/31 ; 522/50; 522/59; 526/193; 526/198

Current International Class: C08F 4/00 (20060101)

Field of Search: 522/31,50,59 526/193,198

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Primary Examiner: Berman; Susan
Attorney, Agent or Firm: Lown; Jean A.

Claims

We claim:

1. A composition comprising: an electron donor comprising an arylsulfinate salt having a anion of Formula I Ar.sup.1--SO.sub.2.sup.- I and a cation having at least one carbon atom and either a positively charged nitrogen atom or a positively charged phosphorus atom, said electron donor having an oxidation potential in N,N-dimethylformamide of 0.0 to +0.4 volts versus a silver/silver nitrate reference electrode, wherein Ar.sup.1 is a substituted phenyl, an unsubstituted or substituted C.sub.7-30 aryl, or an unsubstituted or substituted C.sub.3-30 heteroaryl, said substituted Ar.sup.1 having a substituent that is an electron withdrawing group or an electron withdrawing group in combination with an electron donating group; the cation is selected from 1) a phosphorous-containing cation of Formula III ##STR00004## where each R.sup.2 is independently an unsubstituted alkyl, an alkyl substituted with a hydroxy, an unsubstituted aryl, or an aryl substituted wit an alkyl, hydroxy, or combinations thereof; or 2) a nitrogen-containing cation having a ring structure comprising a 4 to 12 member heterocyclic group having a positively charged nitrogen atom, said heterocyclic being saturated or unsaturated and having up to 3 heteroatoms selected from oxygen, sulfur, nitrogen, or combinations thereof, wherein said ring structure is unsubstituted or substituted with a substituent selected from an alkyl, aryl, acyl, alkoxy, aryloxy, halo, mercapto, amino, hydroxy, azo, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, or combinations thereof; and an electron acceptor having a reduction potential in N,N-dimethylformamide of +0.4 to -1.0 volts versus a silver/silver nitrate reference electrode.

2. The composition of claim 1, wherein the Ar.sup.1 group of the arylsulfinate salt is anthryl, naphthyl, acenaphthyl, phenanthryl, phenanthrenyl, perylenyl, anthracenyl, anthraquinonyl, anthronyl, biphenyl, terphenyl, 9,10-dihydroanthracenyl, or fluorenyl, said Ar.sup.1 group being unsubstituted or substituted with an electron withdrawing group or an electron withdrawing group in combination with an electron donating group.

3. The composition of claim 1, wherein the Ar.sup.1 group of the arylsulfinate salt is quinolinyl, isoquinolinyl, quinazolinyl, quinoxalinyl, cinnolinyl, benzofuranyl, benzomercaptophenyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, indolyl, phthalazinyl, benzothiadiazolyl, benzotriazinyl, phenazinyl, phenanthridinyl, acridinyl, or indazolyl, said Ar.sup.1 group being unsubstituted or substituted with an electron withdrawing group or an electron withdrawing group in combination with an electron donating group.

4. The composition of claim 1, wherein the Ar.sup.1 group of the arylsulfinate salt is a substituted phenyl, an unsubstituted or substituted naphthyl, or an unsubstituted or substituted anthraquinonyl, said substituted Ar.sup.1 having a substituent that is an electron withdrawing group or an electron withdrawing group in combination with an electron donating group.

5. The composition of claim 1, wherein the Ar.sup.1 group is phenyl substituted with an electron withdrawing group selected from halo, cyano, fluoroalkyl, pertluoroalkyl, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo, alkoxysulfonyl, aryloxysulfonyl, perfluoroalkylsulfonyl, alkylsulfonyl, azo, alkenyl, alkynyl, dialkylphosphonato, diarylphosphonato, aminocarbonyl, or combinations thereof.

6. The composition of claim 1, wherein the anion of the arylsulfinate salt is 4-chlorobenzenesulfinate, 4-cyanobenzenesulfinate, 4-ethoxycarbonylbenzenesulfinate, 4-trifluoromethylbenzenesulfinate, 3-trifluoromethylbenzenesulfinate, 1-anthraquinone sulfinate, 1-naphthalenesulfinate, or 2-naphthalenesulfinate.

7. The composition of claim 1, wherein the cation of the arylsulfinate salt is the ring structure comprising a 5 member heterocyclic group, a 5 member heterocyclic group fused to an aromatic ring having 0 to 3 heteroatoms, a 6 member heterocyclic group, or a 6 member heterocyclic group fused to an aromatic ring having 0 to 3 heteroatoms, wherein said ring structure is unsubstituted or substituted with a substituent selected from an alkyl, aryl, acyl, alkoxy, aryloxy, halo, mercapto, amino, hydroxy, azo, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, or combinations thereof.

8. The composition of claim 1, wherein said heterocyclic group is bicyclic.

9. The composition of claim 1, wherein said heterocyclic group is fused to a cyclic or bicyclic group that is saturated or unsaturated and that has 0 to 3 heteroatoms.

10. The composition of claim 1, wherein said heterocyclic group is fused to an aromatic ring having 0 to 3 heteroatoms.

11. The composition of claim 1, wherein the cation of the arylsulfinate salt is of Formula III where each R.sup.2 is independently an unsubstituted aryl or an aryl substituted with an alkyl, hydroxy, or combinations thereof.

12. The composition of claim 1, wherein the electron acceptor is an iodonium salt, a hexaarylbisimidizole, a persulfate, a peroxide, or a metal ion in an oxidized state.

13. The composition of claim 1, further comprising a sensitizing compound capable of absorbing a wavelength of actinic radiation in the range of 250 to 1000 nanometer.

14. The composition of claim 13, wherein the electron acceptor is a diaryliodonium salt, a hexaarylbisimidizole, or combinations thereof.

15. The composition of claim 13, wherein the electron acceptor has an electron potential in the range of 0.0 to -1.0 volts versus a silver/silver nitrate reference electrode.

16. The composition of claim 1, further comprising an ethylenically unsaturated monomer.

17. The composition of claim 16, wherein the ethylenically unsaturated monomer comprises a monoacrylate, monomethacrylate, diacrylate, dimethacrylate, polyacrylate, polymethacrylate, or combinations thereof, wherein said monomer is unsubstituted or substituted with a hydroxy.

18. The composition of claim 13, wherein the composition further comprises a hydroxy-containing material selected from an alcohol, a hydroxy-containing monomer, or combinations thereof.

19. The composition of claim 1, wherein the cation comprises tetraphenylphosphonium that is unsubstituted or substituted.

20. The composition of claim 1, wherein the cation comprises an imidazolium ion or oxazolium ion that is unsubstituted or substituted.

21. The composition of claim 1, wherein the cation comprises benzoxazolium ion or benzothiazolium ion that is unsubstituted or substituted.

22. The composition of claim 1, wherein the cation comprises a pyridinium ion or morpholinium ion that is unsubstituted or substituted.

23. The composition of claim 1, wherein the cation comprises N-alkylated 1,4-diazabicyclo[2.2.2]octane, N-protonated 1,4-diazabicyclo[2.2.2]octane, N-alkylated 1-azabicyclic[2.2.2]octane, or N-protonated 1,4-diazabicyclo[2.2.2]octane that is unsubstituted or substituted.

Description

TECHNICAL FIELD

Arylsulfinate salts are provided that can be used as electron donors in initiator systems for free radical polymerization reactions.

BACKGROUND

Free radical polymerization reactions typically have an initiator system. The initiator systems can be based on various chemical approaches. For example, free radical polymerization reactions can be initiated using a three-component photoinitiator system that includes an electron acceptor, an electron donor, and a sensitizing compound. Alternatively, an electron donor in combination with a sensitizing compound can be used as a photoinitiator system. Free radical polymerization reactions also can be initiated using a two-component thermal initiator system that includes an electron acceptor and an electron donor.

In thermally initiated free radical polymerization reactions, an electron donor usually reacts directly with an electron acceptor to reduce the electron acceptor. The reduced electron acceptor can be a radical that can function as an initiating free radical for the polymerization reaction. The reaction between the electron donor and acceptor can occur at room temperature or at elevated temperatures. The electron acceptor and the electron donor are often kept in separate containers (i.e., not mixed together) until polymerization is desired.

In contrast to thermally initiated systems, the components of a photoinitiator system usually can be mixed together prior to use. In a three-component photoinitiator system that includes an electron donor, electron acceptor and a sensitizing compound, there is typically no direct reaction between the electron donor and the electron acceptor. Rather, the sensitizing compound usually absorbs actinic radiation resulting in the formation of an excited sensitizing compound. The electron donor can donate an electron to the excited sensitizing compound. That is, the sensitizing compound is reduced and the electron donor is oxidized. The reduced sensitizing compound is a radical anion that can donate an electron to an electron acceptor to yield an initiating free radical for the polymerization reaction. The initiating free radical is the reduced electron acceptor. In some instances of a three-component photoinitiator system, the oxidized electron donor is a radical species that also can function as an initiating free radical.

Other photoinitiator systems include a sensitizing compound and an electron donor but no electron acceptor. The sensitizing compound can absorb actinic radiation to form an exited sensitizing compound. The electron donor can donate an electron to the excited sensitizing compound resulting in the oxidation of the electron donor. The oxidized electron donor is a radical species that functions as an initiating free radical for polymerization reactions.

SUMMARY

Compositions are provided that include an electron donor and an electron acceptor. More specifically, the electron donor is an arylsulfinate salt. Methods of polymerization are provided that can be used to prepare polymeric material using a free radical polymerization reaction. The polymerization reaction is initiated with a photoinitiator system, thermal initiator system, or combinations thereof.

One aspect of the invention provides a composition that includes an electron donor and an electron acceptor. The electron donor has an oxidation potential in N,N-dimethylformamide of 0.0 to +0.4 volts versus a silver/silver nitrate reference electrode and includes an arylsulfinate salt having an anion of Formula I Ar.sup.1--SO.sub.2.sup.- I and having a cation that contains at least one carbon atom and either a positively charged nitrogen atom or a positively charged phosphorus atom. The Ar.sup.1 group in Formula I is a substituted phenyl, an unsubstituted or substituted C.sub.7-30 aryl, or an unsubstituted or substituted C.sub.3-30 heteroaryl. A substituted Ar.sup.1 group can have a substituent that is an electron withdrawing group or an electron withdrawing group in combination with an electron donating group. The electron acceptor has a reduction potential in N,N-dimethylformamide of +0.4 to -1.0 volts versus a silver/silver nitrate reference electrode. The composition can further include a sensitizing compound, ethylenically unsaturated monomers, hydroxy-containing material, or combinations thereof.

A second aspect of the invention provides a photopolymerization method that includes irradiating a photopolymerizable composition with actinic radiation until the photopolymerizable composition gels or hardens. The photopolymerizable composition includes an ethylenically unsaturated monomer, a sensitizing compound, an electron donor, and an electron acceptor. The sensitizing compound is capable of absorbing a wavelength of actinic radiation in the range of 250 to 1000 nanometers. The electron acceptor has a reduction potential in N,N-dimethylformamide of +0.4 to -1.0 volts versus a silver/silver nitrate reference electrode and forms a colorless solution when dissolved in an alcohol or an ethylenically unsaturated monomer. The electron donor has an oxidation potential in N,N-dimethylformamide of 0.0 to +0.4 volts versus a silver/silver nitrate reference electrode and includes an arylsulfinate salt. The arylsulfinate salt has an anion of Formula I Ar.sup.1--SO.sub.2.sup.- I and a cation that contains at least one carbon atom and either a positively charged nitrogen atom or a positively charged phosphorus atom. The Ar.sup.1 group in Formula I is a substituted phenyl, an unsubstituted or substituted C.sub.7-30 aryl, or an unsubstituted or substituted C.sub.3-30 heteroaryl. A substituted Ar.sup.1 group can have a substituent that is an electron withdrawing group or an electron withdrawing group in combination with an electron donating group.

A third aspect of the invention provides a method of polymerization that includes forming a polymerizable composition and reacting the polymerizable composition. The polymerizable composition includes an ethylenically unsaturated monomer, an electron donor having an oxidation potential in N,N-dimethylformamide of 0.0 to +0.4 volts versus a silver/silver nitrate reference electrode, and an electron acceptor having a reduction potential in N,N-dimethylformamide of +0.4 to -1.0 volts versus a silver/silver nitrate reference electrode. The electron donor is an arylsulfinate salt having an anion of Formula I Ar.sup.1--SO.sub.2.sup.- I and having a cation that contains at least one carbon atom and either a positively charged nitrogen atom or a positively charged phosphorus atom. The Ar.sup.1 group in Formula I is a substituted phenyl, an unsubstituted or substituted C.sub.7-30 aryl, or an unsubstituted or substituted C.sub.3-30 heteroaryl. A substituted Ar.sup.1 group can have a substituent that is an electron withdrawing group or an electron withdrawing group in combination with an electron donating group.

The above summary is not intended to describe each disclosed embodiment or every implementation of the present invention. The detailed description section that follow more particularly exemplify these embodiments.

DETAILED DESCRIPTION

Compositions are provided that include an electron donor and an electron acceptor. More specifically, the electron donor is an arylsulfinate salt. Methods of polymerization are also provided that can be used to prepare polymeric material from a polymerizable composition. The polymerizable composition includes an initiator system with an arylsulfinate salt as the electron donor. The initiator system can be a thermal initiator system, photoinitiator system, or combinations thereof.

Definitions

As used herein, the terms "a", "an", and "the" are used interchangeably with "at least one" to mean one or more of the elements being described.

As used herein, the term "actinic radiation" refers to electromagnetic radiation capable of producing photochemical activity.

As used herein, the term "acyl" refers to a monovalent group of formula --(CO)R.sup.a where R.sup.a is an alkyl or aryl group.

As used herein, the term "alkenyl" refers to a monovalent radical of an alkene (i.e., an alkene is an aliphatic compound having at least one carbon-carbon double bond).

As used herein, the term "alkoxy" refers to a group of formula --OR where R is an alkyl group. Examples include methoxy, ethoxy, propoxy, butoxy, and the like.

As used herein, the term "alkoxycarbonyl" refers to a monovalent group of formula --(CO)OR where R is an alkyl group. An example is ethoxycarbonyl.

As used herein, the term "alkoxysulfonyl" refers to a monovalent group having the formula --SO.sub.3R where R is an alkyl group.

As used herein, the term "alkyl" refers to a monovalent radical of an alkane. The alkyl can be linear, branched, cyclic, or combinations thereof and typically contains 1 to 30 carbon atoms. In some embodiments, the alkyl group contains 1 to 20, 1 to 14, 1 to 10, 4 to 10, 4 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, n-hexyl, cyclohexyl, n-octyl, n-heptyl, and ethylhexyl.

As used herein, the term "alkylsulfonyl" refers to a monovalent group of formula --SO.sub.2R where R is an alkyl group.

As used herein, the term "alkynyl" refers to a monovalent radical of an alkyne (i.e., an alkyne is an aliphatic compound having at least one carbon-carbon triple bond).

As used herein, the term "amino" refers to a monovalent group of formula --NR.sup.b.sub.2 where each R.sup.b is independently a hydrogen, alkyl, or aryl group. In a primary amino group, each R.sup.b group is hydrogen. In a secondary amino group, one of the R.sup.b groups is hydrogen and the other R.sup.b group is either an alkyl or aryl. In a tertiary amino group, both of the R.sup.b groups are an alkyl or aryl.

As used herein, the term "aminocarbonyl" refers to a monovalent group of formula --(CO)NR.sup.b.sub.2 where each R.sup.b is independently a hydrogen, alkyl, or aryl.

As used herein, the term "aromatic" refers to both carbocyclic aromatic compounds or groups and heteroaromatic compounds or groups. A carbocyclic aromatic compound is a compound that contains only carbon atoms in an aromatic ring structure. A heteroaromatic compound is a compound that contains at least one heteroatom selected from S, O, N, or combinations thereof in an aromatic ring structure.

As used herein, the term "aryl" refers to a monovalent aromatic carbocyclic radical. The aryl can have one aromatic ring or can include up to 5 carbocyclic ring structures that are connected to or fused to the aromatic ring. The other ring structures can be aromatic, non-aromatic, or combinations thereof. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, terphenyl, anthryl, naphthyl, acenaphthyl, anthraquinonyl, phenanthryl, anthracenyl, pyrenyl, perylenyl, and fluorenyl.

As used herein, the term "aryloxy" refers to a monovalent group of formula --OAr where Ar is an aryl group.

As used herein, the term "aryloxycarbonyl" refers to a monovalent group of formula --(CO)OAr where Ar is an aryl group.

As used herein, the term "aryloxysulfonyl" refers to a monovalent group having the formula --SO.sub.3Ar where Ar is an aryl group.

As used herein, the term "azo" refers to a divalent group of formula --N.dbd.N --.

As used herein, the term "carbonyl" refers to a divalent group of formula --(CO)-- where the carbon atom is connected to the oxygen atom by a double bond.

As used herein, the term "carboxy" refers to a monovalent group of formula --(CO)OH.

As used herein, the term "conjugated" refers to unsaturated compounds having at least two carbon-carbon double or triple bonds with alternating carbon-carbon single bonds and carbon-carbon double or triple bonds.

As used herein, the term "cyano" refers to a group of formula --CN.

As used herein, the term "dialkylphosphonato" refers to a group of formula --(PO)(OR).sub.2 where R is an alkyl. As used herein the formula "(PO)" indicates that the phosphorus atom is attached to an oxygen atom with a double bond.

As used herein, the term "diarylphosphonato" refers to a group of formula --(PO)(OAr).sub.2 where Ar is an aryl.

As used herein, the term "electron donating" refers to a substituent that can donate electrons. Suitable examples include, but are not limited to, a primary amino, secondary amino, tertiary amino, hydroxy, alkoxy, aryloxy, alkyl, or combinations thereof.

As used herein, the term "electron withdrawing" refers to a substituent that can withdraw electrons. Suitable examples include, but are not limited to, a halo, cyano, fluoroalkyl, perfluoroalkyl, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo, alkoxysulfonyl, aryloxysulfonyl, perfluoroalkylsulfonyl, alkylsulfonyl, azo, alkenyl, alkynyl, dialkylphosphonato, diarylphosphonato, aminocarbonyl, or combinations thereof.

As used herein, the term "fluoroalkyl" refers to an alkyl group that has at least one hydrogen atom replaced with a fluorine atom.

As used herein, the term "formyl" refers to a monovalent group of formula --(CO)H where the carbon is attached to the oxygen atom with a double bond.

As used herein, the term "halo" refers to a halogen group (i.e., F, Cl, Br, or I). In some embodiments, the halo group is F or Cl.

As used herein, the term "halocarbonyl" refers to a monovalent group of formula --(CO)X where X is a halogen group (i.e., F, Cl, Br, or I).

As used herein, the term "heteroaryl" refers to a monovalent radical having a five to seven member aromatic ring that includes one or more heteroatoms independently selected from S, O, N, or combinations thereof in the ring. Such a heteroaryl ring can be connected to or fused to up to five ring structures that are aromatic, aliphatic, or combinations thereof. Examples of heteroaryl groups include, but are not limited to, quinolinyl, isoquinolinyl, quinazolinyl, quinoxalinyl, cinnolinyl, benzofuranyl, benzomercaptophenyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, indolyl, phthalazinyl, benzothiadiazolyl, benzotriazinyl, phenazinyl, phenanthridinyl, acridinyl, and indazolyl, and the like. A heteroaryl is a subset of a heterocyclic group.

As used herein, the term "heterocyclic" refers to a monovalent radical having a ring structure that is saturated or unsaturated and that includes one or more heteroatoms independently selected from S, O, N, or combinations thereof in the ring. The heterocyclic group can be a single ring, bicyclic, or can be fused to another cyclic or bicyclic group. The fused cyclic or bicyclic group can be saturated or unsaturated and can be carbocyclic or contain heteroatoms.

As used herein, the term "hydroxy" refers to a group of formula --OH.

As used herein, the term "mercapto" refers to a group of formula --SH.

As used herein, the term "perfluoroalkyl" refers to an alkyl group that has all the hydrogen atoms replaced with fluorine atoms. A perfluoroalkyl is a subset of a fluoroalkyl.

As used herein, the term "perfluoroalkylsulfonyl" refers to a monovalent group of formula --SO.sub.2R.sub.f where R.sub.f is a perfluoroalkyl.

As used herein, the term "polymerization" refers to forming a higher weight material from monomer or oligomers. The polymerization reaction also can involve a cross-linking reaction.

As used herein when referring to a composition containing an initiator system and polymerizable material, the term "self-stable" means that the composition can be stored for at least one day without any visible gel formation at room temperature (i.e., 20.degree. C. to 25.degree. C.).

As used herein when referring to a compound, the term "oxidative stability" refers to the length of time needed to oxidize 50 weight percent of the compound (t.sub.1/2) at room temperature (i.e., 20.degree. C. to 25.degree. C.) which can be calculated using pseudo-first order kinetics as described in K. A. Connors, Chemical Kinetics: The Study of Reaction Rates in Solution, Chapter 2, VCH, New York, 1990.

As used herein, the term "sulfo" refers to a group having the formula --SO.sub.3H.

Compositions

A variety of materials are known for use as an electron donor in initiator systems for polymerization reactions. However, some of these materials have limited solubility in ethylenically unsaturated monomers. Further, some of these materials have limited oxidative stability, shelf-stability, or combinations thereof.

One aspect of the invention provides a composition that includes an electron donor and an electron acceptor. More specifically, the electron donor includes an arylsulfinate salt. The compositions can be used as initiator systems for free radical polymerization reactions. The initiator systems can be used in photopolymerization methods, thermal polymerization methods, or combinations thereof.

The electron donor has an oxidation potential in N,N-dimethylformamide of 0.0 to +0.4 volts versus a silver/silver nitrate reference electrode and is an arylsulfinate salt having an anion of Formula I Ar.sup.1--SO.sub.2.sup.- I and having a cation that contains at least one carbon atom and either a positively charged nitrogen atom or a positively charged phosphorus atom. The Ar.sup.1 group in Formula I is a substituted phenyl, an unsubstituted or substituted C.sub.7-30 aryl, or an unsubstituted or substituted C.sub.3-30 heteroaryl. A substituted Ar.sup.1 group can have a substituent that is an electron withdrawing group or an electron withdrawing group in combination with an electron donating group. The electron acceptor has a reduction potential in N,N-dimethylformamide of +0.4 to -1.0 volts versus a silver/silver nitrate reference electrode.

The electron donor is selected to have an oxidation potential and the electron acceptor is selected to have a reduction potential in a stated range. The oxidation and reduction potentials can be determined using cyclic voltammetry. As described herein, the oxidation and reduction potentials are measured by dissolving the compound of interest in a non-aqueous solvent (i.e., N,N-dimethylformamide) containing a supporting electrolyte (i.e., 0.1 moles/liter tetrabutylammonium hexafluorophosphate). The resulting solution is purged with an inert gas such as argon. A three-electrode configuration is used that includes a working electrode (i.e., a glassy carbon electrode), a reference electrode (i.e., a silver wire in a 0.01 moles/liter of silver nitrate dissolved in acetonitrile), and a counter electrode (i.e., a platinum wire). The oxidation or reduction potential is the voltage corresponding to the maximum current for the oxidation or reduction reaction.

One component of the composition is the electron donor. The electron donor is an arylsulfinate salt. The arylsulfinate salt is typically soluble in monomers capable of undergoing free radical polymerization reactions and in a variety of non-polar and polar solvents. As used herein, the term "soluble" refers to a compound that can be dissolved in an amount at least equal to 0.05 moles/liter, at least equal to 0.07 moles/liter, at least equal to 0.08 moles/liter, at least equal to 0.09 moles/liter, or at least equal to 0.1 moles/liter in a given material such as a solvent or monomer.

In some arylsulfinate salts, the Ar.sup.1 group is a substituted phenyl or an unsubstituted or substituted C.sub.7-30 aryl group having a carbocyclic aromatic ring. The aryl group can have a single carbocyclic aromatic ring or can have additional carbocyclic rings that are fused or connected to the carbocyclic aromatic ring. Any fused or connected rings can be saturated or unsaturated. The aryl often contains up to 5 rings, up to 4 rings, up to 3 rings, up to 2 rings, or one ring. The aryl group usually has up to 30 carbon atoms, up to 24 carbon atoms, up to 18 carbon atoms, up to 12 carbon atoms, or 6 carbon atoms. Examples of aryl groups having a single ring or multiple fused rings include, but are not limited to, phenyl, anthryl, naphthyl, acenaphthyl, phenanthryl, phenanthrenyl, perylenyl, and anthracenyl. A single bond, methylene group (i.e., --C(R.sup.b).sub.2-- where each R.sup.b is independently hydrogen, alkyl, or aryl), carbonyl group (i.e., --(CO)--), or combinations thereof can connect multiple rings. Examples of aryl groups having multiple connected rings include, but are not limited to, anthraquinonyl, anthronyl, biphenyl, terphenyl, 9,10-dihydroanthracenyl, and fluorenyl.

In other arylsulfinate salts, the Ar.sup.1 group in Formula I can be an unsubstituted or substituted heteroaryl that has a five to seven member aromatic ring that contains one or more heteroatoms independently selected from S, O, N, or combinations thereof in the ring. The heteroaryl can have a single ring or can have multiple rings connected or fused together. Any additional connected or fused rings can be carbocyclic or contain a heteroatom and can be saturated or unsaturated. The heteroaryl group often has up to 5 rings, up to 4 rings, up to 3 rings, up to 2 rings, or one ring. The heteroaryl typically contains up to 30 carbon atoms. In some embodiments, the heteroaryl contains up to 20 carbon atoms, up to 10 carbon atoms, or up to 5 carbon atoms. Examples of heteroaryl groups include, but are not limited to, quinolinyl, isoquinolinyl, quinazolinyl, quinoxalinyl, cinnolinyl, benzofuranyl, benzomercaptophenyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, indolyl, phthalazinyl, benzothiadiazolyl, benzotriazinyl, phenazinyl, phenanthridinyl, acridinyl, azaphenanthrenyl, and indazolyl.

The Ar.sup.1 group in Formula I, in some embodiments, can be substituted with an electron withdrawing group or an electron withdrawing group in combination with an electron donating group provided that the arylsulfinate salt has an oxidation potential in N,N-dimethylformamide of 0.0 to +0.4 volts versus a silver/silver nitrate reference electrode. Electron donating groups can be selected, for example, from a primary amino, secondary amino, tertiary amino, hydroxy, alkoxy, aryloxy, alkyl, or combinations thereof. Electron withdrawing groups can be selected, for example, from a halo, cyano, fluoroalkyl, perfluoroalkyl, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo, alkoxysulfonyl, aryloxysulfonyl, perfluoroalkylsulfonyl, alkylsulfonyl, azo, alkenyl, alkynyl, dialkylphosphonato, diarylphosphonato, aminocarbonyl, or combinations thereof.

In some embodiments, the Ar.sup.1 group includes an electron withdrawing group that is conjugated to the sulfinate group. For example, the Ar.sup.1 group can be a phenyl substituted with an electron withdrawing group selected from halo, cyano, fluoroalkyl, perfluoroalkyl, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo, alkoxysulfonyl, aryloxysulfonyl, perfluoroalkylsulfonyl, alkylsulfonyl, azo, alkenyl, alkynyl, dialkylphosphonato, diarylphosphonato, aminocarbonyl, or combinations thereof.

Specific examples of the arylsulfinate anion of Formula I include, but are not limited to, 4-chlorobenzenesulfinate, 4-cyanobenzenesulfinate, 4-ethoxycarbonylbenzenesulfinate, 4-trifluoromethylbenzenesulfinate, 3-trifluoromethylbenzenesulfinate, 1-naphthalenesulfinate, 2-naphthalenesulfinate, and 1-anthraquinonesulfinate.

The arylsulfinate salts have a cation with at least one carbon atom and either a positively charged nitrogen atom or a positively charged phosphorus atom. In one embodiment, the cation of the arylsulfinate is of Formula II

##STR00001## where R.sup.1 is an alkyl or aryl and each R.sup.4 is independently a hydrogen, alkyl, or aryl. The R.sup.1 and R.sup.4 groups can be unsubstituted or substituted. An alkyl group can be substituted with a hydroxy. An aryl can be substituted with an alkyl, hydroxy, or combinations thereof.

In some examples of Formula II, R.sup.1 and each R.sup.4 group are independently a C.sub.2-30 alkyl that is unsubstituted or substituted with a hydroxy. For example, R.sup.1 and each R.sup.4 independently can be an alkyl group having up to 20, up to 10, up to 8, up to 6, or up to 4 carbon atoms. The alkyl group often has at least 2, at least 3, at least 4, at least 6, or at least 8 carbon atoms. The alkyl group can have 4 to 30, 8 to 30, 3 to 10, 4 to 10, 4 to 8, or 4 to 6 carbon atoms in some compounds. In a specific example, the cation of the arylsulfinate salt is a tetrabutylammonium ion.

In other examples of Formula II, R.sup.1 and two R.sup.4 groups are each independently a C.sub.2-30 alkyl that can be unsubstituted or substituted with a hydroxy. The remaining R.sup.4 group is hydrogen. In still other examples, R.sup.1 and one R.sup.4 group are each independently a C.sub.4-30 alkyl that is unsubstituted or substituted with a hydroxy; and the two remaining R.sup.4 groups are hydrogen. In yet other examples, R.sup.1 is a C.sub.8-30 alkyl that is unsubstituted or substituted with a hydroxy; and the R.sup.4 groups are hydrogen.

The R.sup.1 group and each of the R.sup.4 groups in Formula II independently can be an aryl group that is unsubstituted or substituted with an alkyl, hydroxy, or combinations thereof. An exemplary cation is tetraphenylammonium ion. In another example, R.sup.1 and one R.sup.4 are independently an aryl group that is unsubstituted or substituted with an alkyl, hydroxy, or combinations thereof; and the two remaining R.sup.4 groups are hydrogen. An exemplary cation is diphenylammonium ion.

In other embodiments, the cation of the arylsulfinate salt is a ring structure that includes a 4 to 12 member heterocyclic group with a positively charged nitrogen atom. The heterocyclic group can be saturated or unsaturated and can contain up to three heteroatoms selected from nitrogen, oxygen, sulfur, or combinations thereof (i.e., there is one positively charged nitrogen atom and up to two other heteroatoms selected from nitrogen, oxygen, sulfur, or combinations thereof). The ring structure can be unsubstituted or have a substituent selected from an alkyl, aryl, acyl, alkoxy, aryloxy, halo, mercapto, amino, hydroxy, azo, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, or combinations thereof.

The heterocyclic group in the cationic ring structure can be a single ring, bicyclic, or can be fused to another cyclic or bicyclic group. The fused cyclic or bicyclic group can be saturated or unsaturated and can have 0 to 3 heteroatoms. The ring structure can include up to 30 carbon atoms, up to 24 carbon atoms, up to 18 carbon atoms, up to 12 carbon atoms, up to 6 carbon atoms, or up to 4 carbon atoms and up to 6 heteroatoms, up to 4 heteroatoms, up to 2 heteroatoms, or 1 heteroatom. In some embodiments, the ring structure is a 4 to 12 member heterocyclic group that is a fused to an aromatic ring having 0 to 3 heteroatoms.

Suitable examples of five member heterocyclic groups that contain a positively charged nitrogen atom include, but are not limited to, a pyrrolium ion, pyrazolium ion, pyrrolidinium ion, imidazolium ion, triazolium ion, isoxazolium ion, oxazolium ion, thiazolium ion, isothiazolium ion, oxadiazolium ion, oxatriazolium ion, dioxazolium ion, and oxathiazolium ion. These ions can be unsubstituted or substituted with an alkyl