Compositions comprising cleavable crosslinker and methods
A composition is described comprising a polymer. The polymer comprises polymerized units derived from a cleavable crosslinking monomer. The cleavable crosslinking monomer comprises at least two free-radically polymerizable groups and at least one group having the formula —O—C(R 2 )(R 3 )—O—, wherein R 2 and R 3 are independently hydrogen, alkyl, or aryl. The composition has a Tg no greater than 50° C. In some embodiments, the composition has a storage modulus greater than 3×10 5 Pa at 25° C. and 1 Hz and may be characterized as a non-tacky polymer. In other embodiments, the composition is a pressure sensitive adhesive. Upon cleavage of at least a portion of the polymerized monomeric units derived from the cleavable crosslinking monomer, the composition exhibits a change in at least one physical property. In another embodiment, the composition comprises a polymer and fragments. The fragments comprise the reaction product of a free-radically polymerizable group bonded to a polymer chain and a pendent hydroxyl group. The composition has a Tg no greater than 50° C. Also described are articles, comprising the composition described herein (i.e. before and/or after cleavage); as well as methods of making the composition and methods of making articles.
1. A composition comprising
a polymer comprising polymerized units derived from
a cleavable crosslinking monomer, the cleavable crosslinking monomer comprising at least two free-radically polymerizable groups and at least one group having the formula —O—C(R 2 )(R 3 )—O—, wherein R 2 and R 3 are independently hydrogen, alkyl, or aryl; and
polymerized units derived from alkyl (meth)acrylate monomers having a Tg no greater than 10° C.; and
wherein the composition has a Tg no greater than 50° C. and at least a portion of the polymerized units derived from the cleavable crosslinking monomer are cleaved.
2. The composition of claim 1 wherein the polymer comprises polymerized units derived from one or more non-cyclic alkyl (meth)acrylate monomer(s) having 4 to 20 carbon atoms.
3. The composition of claim 1 wherein the composition has a storage modulus greater than 3×10 5 Pa at 25° C. and 1 Hz.
4. The composition of claim 1 wherein the composition is a pressure sensitive adhesive.
5. The composition of claim 4 wherein the composition has a wet out of less than 5 seconds/in 2 .
6. The composition of claim 1 wherein upon cleavage of at least a portion of the polymerized monomeric units derived from the cleavable crosslinking monomer, the composition exhibits a change in at least one physical property selected from
a) a decrease in polymer gel content of at least 10%;
b) a decrease in storage modulus of at least 10%; and
c) an increase in peel adhesion of at least 10%.
7. The composition of claim 1 wherein the polymer comprises at least 50 wt. % of polymerized units derived from one or more alkyl (meth)acrylate monomer(s) having 4 to 20 carbon atoms.
8. The composition of claim 1 wherein the composition comprises tackifer, plasticizer, or a combination thereof.
9. The composition of claim 1 wherein the composition comprises 0.1 to 20 wt. % of the cleavable crosslinking monomer.
10. The composition of claim 1 wherein the cleavable crosslinking monomer has the formula:
R 1 is hydrogen or methyl;
R 2 and R 3 are independently hydrogen, alkyl, or aryl; and
L 1 is a divalent linking group.
11. The composition of claim 1 wherein the cleavable crosslinking monomer has the formula:
R 1 is hydrogen or methyl;
R 3 is independently hydrogen, alkyl, or aryl; and
L 1 is a divalent linking group.
12. The composition of claim 1 wherein the polymer comprises polymerized units derived from octyl (meth)acrylate.
13. The composition of claim 1 wherein the polymer further comprises polymerized units derived from at least one monomer selected from acid-functional monomers, non-acid functional polar monomers, vinyl monomers, and combinations thereof.
14. The composition of claim 1 wherein the polymer further comprises a non-cleavable crosslinker.
15. The composition of claim 1 wherein the composition further comprises a photoacid generator or thermal acid generator.
16. An article comprising the composition of claim 1 on a substrate.
17. A composition comprising
a polymer comprising polymerized units derived from
a cleavable crosslinking monomer, the cleavable crosslinking monomer comprising at least two free-radically polymerizable groups and at least one group having the formula —O—C(R 2 )(R 3 )—O—, wherein R 2 and R 3 are independently hydrogen, alkyl, or aryl; and
at least 50 wt. % of polymerized units derived from one or more alkyl (meth)acrylate monomer(s) having 4 to 20 carbon atoms;
wherein the composition has a Tg no greater than 50° C. and the polymerized units derived from the cleavable crosslinking monomer are cleaved.
18. The composition of claim 17 wherein the composition has a storage modulus greater than 3×10 5 Pa at 25° C. and 1 Hz.
19. The composition of claim 17 wherein the composition is a pressure sensitive adhesive.
20. The composition of claim 17 wherein upon cleavage of at least a portion of the polymerized monomeric units derived from the cleavable crosslinking monomer, the composition exhibits a change in at least one physical property selected from
a) a decrease in polymer gel content of at least 10%;
b) a decrease in storage modulus of at least 10%; and
c) an increase in peel adhesion of at least 10%.
21. The composition of claim 17 wherein the composition comprises tackifer, plasticizer, or a combination thereof.
22. The composition of claim 17 wherein the composition comprises 0.1 to 20 wt. % of the cleavable crosslinking monomer.
23. The composition of claim 17 wherein the cleavable crosslinking monomer has the formula:
R 1 is hydrogen or methyl;
R 2 and R 3 are independently hydrogen, alkyl, or aryl; and
L 1 is a divalent linking group.
24. The composition of claim 17 wherein the cleavable crosslinking monomer has the formula:
R 1 is hydrogen or methyl;
R 3 is independently hydrogen, alkyl, or aryl; and
L 1 is a divalent linking group.
25. The composition of claim 17 wherein the polymer comprises polymerized units derived from octyl (meth)acrylate.
26. The composition of claim 17 wherein the polymer further comprises polymerized units derived from at least one monomer selected from acid-functional monomers, non-acid functional polar monomers, vinyl monomers, and combinations thereof.
27. The composition of claim 17 wherein the polymer further comprises a non-cleavable crosslinker.
28. The composition of claim 17 wherein the composition further comprises a photoacid generator or thermal acid generator.
29. An article comprising the composition of claim 17 on a substrate.