ADDITION-FRAGMENTATION AGENTS

1 . An addition-fragmentation agent of the formula:

wherein

R 1 , R 2 and R 3 are each independently Z m -Q-, a (hetero)alkyl group or a (hetero)aryl group with the proviso that at least one of R 1 , R 2 and R 3 is Z m -Q-,

Q is a linking group have a valence of m+1;

Z is an ethylenically unsaturated polymerizable group,

m is 1 to 6;

each X 1 is independently —O— or —NR 4 —, where R 4 is H or C 1 -C 4 alkyl, and

n is 0 or 1.

2 . The addition-fragmentation agent of claim 1 where Z comprises a vinyl, vinyloxy, (meth)acryloxy, (meth)acrylamido, styrenic and acetylenic functional groups.

3 . The crosslinking agent of claim 1 where Z is selected from:

wherein R 4 is H or C 1 -C 4 alkyl

4 . The addition-fragmentation agent of claim 1 wherein Q is selected from from —O—. —S—, —NR 4 —, —SO 2 —, —PO 2 —, —CO—, —OCO—, —R 6 —, —NR 4 —CO—NR 4 —, NR 4 —CO—O—, NR 4 —CO—NR 4 —CO—O—R 6 —, —CO—NR 4 —R 6 —, —R 6 —CO—O—R 6 —, —O—R 6 —. —S—R 6 —, —NR 4 —R 6 —, —SO 2 —R 6 —, —PO 2 —R 6 —, —CO—R 6 —, —OCO—R 6 —, —NR 4 —CO—R 6 —, NR 4 —R 6 —CO—O—, and NR 4 —CO—NR 4 —, wherein each R 4 is hydrogen, a C 1 to C 4 alkyl group, or aryl group, each R 6 is an alkylene group having 1 to 6 carbon atoms, a 5- or 6-membered cycloalkylene group having 5 to 10 carbon atoms, or a divalent arylene group having 6 to 16 carbon atoms, with the proviso that Q-Z does not contain peroxidic linkages.

5 . The addition-fragmentation agent of claim 1 where Q is an alkylene.

6 . The addition-fragmentation agent of claim 5 wherein Q is an alkylene of the formula —C r H 2r —, where r is 1 to 10.

7 . The addition-fragmentation agent of claim 1 where Q is a hydroxyl-substituted alkylene.

8 . The addition-fragmentation agent of claim 1 where Q is —CH 2 —CH(OH)—CH 2 —

9 . The addition-fragmentation agent of claim 1 where Q is an aryloxy-substituted alkylene.

10 . The addition-fragmentation agent of claim 1 where R 5 is an alkoxy-substituted alkylene.

11 . The addition-fragmentation agent of claim 1 wherein R 1 —X 1 — groups (and optionally R 2 —X 2 — groups) is selected from H 2 C═C(CH 3 )C(O)—O—CH 2 —CH(OH)—CH 2 —O—, H 2 C═C(CH 3 )C(O)—O—CH 2 —CH(O—(O)C(CH 3 )═CH 2 )—CH 2 —O—, H 2 C═C(CH 3 )C(O)—O—CH(CH 2 OPh)-CH 2 —O—, H 2 C═C(CH 3 )C(O)—O—CH 2 CH 2 —N(H)—C(O)—O—CH(CH 2 OPh)-CH 2 —O—, H 2 C═C(CH 3 )C(O)—O—CH 2 —CH(O—(O)C—N(H)—CH 2 CH 2 —O—(O)C(CH 3 )C═CH 2 )—CH—O—, H 2 C═C(H)C(O)—O—(CH 2 ) 4 —O—CH 2 —CH(OH)—CH 2 —O—, H 2 C═C(CH 3 )C(O)—O—CH 2 —CH(O—(O)C—N(H)—CH 2 CH 2 —O—(O)C(CH 3 )C═CH 2 )—CH 2 —O—, CH 3 —(CH 2 ) 7 —CH(O—(O)C—N(H)—CH 2 CH 2 —O—(O)C(CH 3 )C═CH 2 )—CH 2 —O—, H 2 C═C(H)C(O)—O—(CH 2 ) 4 —O—CH 2 —CH(—O—(O)C(H)═CH 2 )—CH 2 —O— and H 2 C═C(H)C(O)—O—CH 2 —CH(OH)—CH 2 —O—. H 2 C═C(H)C(O)—O—(CH 2 ) 4 —O—CH 2 —CH(—O—(O)C(H)═CH 2 )—CH 2 —O—, and CH 3 —(CH 2 ) 7 —CH(O—(O)C—N(H)—CH 2 CH 2 —O—(O)C(CH 3 )C═CH 2 )—CH 2 —O—.

12 . A polymerizable composition comprising the addition-fragmentation agent of claim 1 , at least one free-radically polymerizable monomer, and an initiator.

13 . The polymerizable composition of claim 12 comprising:

a) 85 to 100 parts by weight of an (meth)acrylic acid ester of non-tertiary alcohol;

b) 0 to 15 parts by weight of an acid functional ethylenically unsaturated monomer;

c) 0 to 10 parts by weight of a non-acid functional, ethylenically unsaturated polar monomer;

d) 0 to 5 parts vinyl monomer; and

e) 0 to 5 parts of a multifunctional (meth)acrylate;

based on 100 parts by weight total monomer, and

f) 0.1 to 10 parts by weight of the addition-fragmentation agent, based on 100 parts by weight of a) to e).

14 . The polymerizable composition of claim 13 further comprising 0.01 to 5 parts of a multifunctional (meth)acrylate.

15 . The polymerizable composition of claim 12 further comprising a free radical initiator.

16 . The polymerizable composition of claim 15 wherein the initiator is a thermal initiator.

17 . A method of making the addition-fragmentation agent of claim 1 comprising the step of reacting a compound of the formula:

wherein X 2 comprises an electrophilic or nucleophilic functional group,

X 3 is X 2 , X 1 —R 2 or X 1 —R 3 , and

n is 0 or 1;

with a compound of the formula:

wherein

A is a functional group that is co-reactive with functional group X 2 , R 4 is hydrogen, a C 1 to C 4 alkyl group, or aryl group; R 5 is a single bond or a divalent (hetero)hydrocarbyl linking group that joins the ethylenically unsaturated group to reactive functional group A.

18 . The method of claim 17 wherein R 5 is selected from a single bond or a divalent linking group that joins an ethylenically unsaturated group to co-reactive functional group A.

19 . The method of claim 17 wherein R 5 is selected from —O—. —S—, —NR 4 —, —SO 2 —, —PO 2 —, —CO—, —OCO—, —NR 4 —CO—, NR 4 —CO—O—, NR 4 —CO—NR 4 —, —R 6 — and combinations thereof, where R 6 is an alkylene group having 1 to 6 carbon atoms, a 5- or 6-membered cycloalkylene group having 5 to 10 carbon atoms, or a divalent arylene group having 6 to 16 carbon atoms.

20 . The method of claim 17 wherein the co-reactive functional group A is selected from hydroxyl, amino, oxazolinyl, oxazolonyl, acetyl, acetonyl, carboxyl, isocyanato, epoxy, aziridinyl, acyl halide, vinyloxy, and cyclic anhydride groups.

21 . The method of claim 17 ,

where the reactive functional group X 2 is isocyanato functional group, the co-reactive functional group A comprises a secondary amino or hydroxyl group;

where the reactive functional group X 2 comprises a hydroxyl group, the co-reactive functional group comprises a carboxyl, ester, acyl halide, isocyanato, epoxy, anhydride, azlactonyl or oxazolinyl group;

where the reactive functional group X 2 comprises a carboxyl group, the co-reactive functional group A comprises a hydroxyl, amino, epoxy, isocyanate, or oxazolinyl group.