Highly efficient free radical photopolymerizations through enabled dark cure
A quaternary ammonium salt comprising a chromophore constituent, a tertiary amine cation constituent connected to the para-position of the chromophore constituent via a methylene linkage, and a borate anion constituent, wherein chromophore constituent is a 3-ketocoumarin constituent or a benzophenone constituent. Also, a photobase-redox initiating system comprising the quaternary ammonium salt and a peroxide.
1. A quaternary ammonium salt comprising a chromophore constituent, a tertiary amine cation constituent connected to the para-position of the chromophore constituent via a methylene linkage, and a borate anion constituent, wherein chromophore constituent is a 3-ketocoumarin constituent and the quaternary ammonium salt has the formula (I)
wherein:
R 1 and R 2 , identical or different, are independently selected from the group consisting of —H, —OH, linear or branched C 1 -C 8 -alkoxy group,
where R″ is a linear or branched C 1 -C 8 alkyl group, unsubstituted or substituted -phenyl group, unsubstituted or substituted -naphthyl group, unsubstituted or substituted -vinyl group, -halogen, and halogenated C 1 -C 8 -alkyl group;
R 3 is selected from the group consisting of independently selected from the group consisting of —H, —OH, linear or branched C 1 -C 8 -alkoxy group, -halogen, and halogenated -alkyl group;
R 4 is selected from the group consisting of independently selected from the group consisting of —H, —OH, linear or branched C 1 -C 8 -alkoxy group, -halogen, and halogenated C 1 -C 8 -alkyl group;
R 5 , identical or different, is independently selected from the group consisting of linear or branched C 1 -C 8 N-alkyl group; hydroxyl-substituted C 1 -C 8 N-alkyl group; fused 5-7 member heterocyclic ring; and unsubstituted or substituted aromatic ring, wherein the substituent on the aromatic ring is selected from the group consisting of linear or branched C 1 -C 8 alkyl group and linear or branched C 1 -C 8 alkoxy group; and
R 6 , identical or different, is independently selected from the group consisting of linear or branched C 1 -C 8 alkyl group, and unsubstituted or substituted aromatic ring wherein the substituent on the aromatic ring is selected from the group consisting of linear or branched C 1 -C 8 alkyl group, linear or branched C 1 -C 8 alkoxy group, and halogen.
2. The quaternary ammonium salt of claim 1 , wherein each alkoxy group is independently selected from the group consisting of methoxy and butoxy.
3. The quaternary ammonium salt of claim 2 , wherein R 3 is —H or linear or branched C 1 -C 8 -alkoxy.
4. The quaternary ammonium salt of claim 1 , wherein R 3 is —H.
5. The quaternary ammonium salt of claim 1 , wherein:
the substituted -phenyl group has one or more independently selected substituents selected from the group consisting of linear or branched C 1 -C 8 alkyl group, linear or branched C 1 -C 8 -alkoxy group, -halogen, and halogenated C 1 -C 6 -alkyl group;
the substituted -naphthyl group has one or more independently selected substituents selected from the group consisting of linear or branched C 1 -C 8 alkyl group, linear or branched C 1 -C 8 -alkoxy group, -halogen, and halogenated C 1 -C 6 -alkyl group; and
the unsubstituted vinyl group is C 2 and the substituted vinyl group is an extended vinylene up to C 10 .
6. The quaternary ammonium salt of claim 1 , wherein at least one of the R 5 groups is the substituted aromatic ring.
7. A quaternary ammonium salt comprising a chromophore constituent, a tertiary amine cation constituent connected to the para-position of the chromophore constituent via a methylene linkage, and a borate anion constituent, wherein chromophore constituent is a 3-ketocoumarin constituent and the quaternary ammonium salt has the formula (I) or the chromophore constituent is a benzophenone constituent and the quaternary ammonium salt has the formula (II)
wherein
R 1 and R 2 , identical or different, are independently selected from the group consisting of —H, —OH, linear or branched C 1 -C 8 -alkoxy group,
where R″ is a linear or branched C 1 -C 8 alkyl group, unsubstituted or substituted -phenyl group, unsubstituted or substituted -naphthyl group, unsubstituted or substituted -vinyl group, -halogen, and halogenated C 1 -C 8 -alkyl group;
R 3 is selected from the group consisting of independently selected from the group consisting of —H, —OH, linear or branched C 1 -C 8 -alkoxy group, -halogen, and halogenated -alkyl group;
R 4 is selected from the group consisting of independently selected from the group consisting of —H, —OH, linear or branched C 1 -C 8 -alkoxy group, -halogen, and halogenated C 1 -C 8 -alkyl group;
R 5 , identical or different, is independently selected from the group consisting of linear or branched C 1 -C 8 N-alkyl group; hydroxyl-substituted C 1 -C 8 N-alkyl group; fused 5-7 member heterocyclic ring; and unsubstituted or substituted aromatic ring, wherein the substituent on the aromatic ring is selected from the group consisting of linear or branched C 1 -C 8 alkyl group and linear or branched C 1 -C 8 alkoxy group; and
R 6 , identical or different, is independently selected from the group consisting of linear or branched C 1 -C 8 alkyl group, and unsubstituted or substituted aromatic ring wherein the substituent on the aromatic ring is selected from the group consisting of linear or branched C 1 -C 8 alkyl group, linear or branched C 1 -C 8 alkoxy group, and halogen; and
wherein the amine cation constituent is selected from the group consisting of N-methyl morpholine, N-methyl pyrrolidine, N,N-dimethyl aniline, N,N,4-trimethyl aniline, N,N-dimethyl-4-methoxyaniline, N,N-pyrrolidine-4-methoxyaniline, and N,N-ethoxy-4-methylaniline.
8. The quaternary ammonium salt of claim 1 , wherein the borate anion constituent is selected from the group consisting of tetraphenyl borate, tetra-4-methyl-phenyl borate, tetra-4-methoxy-phenyl borate, tetra-4-fluoro-phenyl borate, n-butyl-triphenyl borate, s-butyl-triphenyl borate, t-butyl-triphenyl borate, cyclohexyl-triphenyl borate, di-n-butyl-diphenyl borate, tri-n-butyl-phenyl borate, and tetra-n-butyl borate.
9. The quaternary ammonium salt of claim 1 , wherein the 3-ketocoumarin constituent is selected from the group consisting of dimethoxy-ketocoumarin, di-n-butoxy-ketocoumarin, difluoro-ketocoumarin, diphenyl-ketocoumarin, divinyl-ketocoumarin, trimethoxy-ketocoumarin, tetramethoxy-ketocoumarin, 3,4-benzo-ketocoumarin, and 4,5-benzo-ketocoumarin.
10. A photobase-redox initiating system comprising a quaternary ammonium salt and a peroxide,
wherein the quaternary ammonium salt comprises a chromophore constituent, a tertiary amine cation constituent connected to the para-position of the chromophore constituent via a methylene linkage, and a borate anion constituent, wherein chromophore constituent is a 3-ketocoumarin constituent and the quaternary ammonium salt has the formula (I) or the chromophore constituent is a benzophenone constituent and the quaternary ammonium salt has the formula (II)
wherein
R 1 and R 2 , identical or different, are independently selected from the group consisting of —H, —OH, linear or branched C 1 -C 8 -alkoxy group,
where R″ is a linear or branched C 1 -C 8 alkyl group, unsubstituted or substituted -phenyl group, unsubstituted or substituted -naphthyl group, unsubstituted or substituted -vinyl group, -halogen, and halogenated C 1 -C 8 -alkyl group;
R 3 is selected from the group consisting of independently selected from the group consisting of —H, —OH, linear or branched C 1 -C 8 -alkoxy group, -halogen, and halogenated -alkyl group;
R 4 is selected from the group consisting of independently selected from the group consisting of —H, —OH, linear or branched C 1 -C 8 -alkoxy group, -halogen, and halogenated C 1 -C 8 -alkyl group;
R 5 , identical or different, is independently selected from the group consisting of linear or branched C 1 -C 8 N-alkyl group; hydroxyl-substituted C 1 -C 8 N-alkyl group; fused 5-7 member heterocyclic ring; and unsubstituted or substituted aromatic ring, wherein the substituent on the aromatic ring is selected from the group consisting of linear or branched C 1 -C 8 alkyl group and linear or branched C 1 -C 8 alkoxy group; and
R 6 , identical or different, is independently selected from the group consisting of linear or branched C 1 -C 8 alkyl group, and unsubstituted or substituted aromatic ring wherein the substituent on the aromatic ring is selected from the group consisting of linear or branched C 1 -C 8 alkyl group, linear or branched C 1 -C 8 alkoxy group, and halogen; and
wherein the peroxide is selected from the group consisting of benzoyl peroxide, dilauroyl peroxide, dialkylperoxydicarbonate, phthaloyl peroxide, dicumyl peroxide, and combinations thereof.
11. The quaternary ammonium salt of claim 1 , wherein the amine cation constituent is selected from the group consisting of N-methyl morpholine, N-methyl pyrrolidine, N,N-dimethyl aniline, N,N,4-trimethyl aniline, N,N-dimethyl-4-methoxyaniline, N,N-pyrrolidine-4-methoxyaniline, and N,N-ethoxy-4-methylaniline.