Acrylic polymers having controlled placement of functional groups
Acrylic copolymers that include the controlled placement of functional groups within the polymer structure are provided. The copolymers contain a reactive segment and a non-reactive segment and are manufactured via a controlled radical polymerization process. The copolymers are useful in the manufacture of adhesives and elastomers.
1. A crosslinkable composition comprising:
at least one acrylic copolymer comprising two reactive segments of controlled molecular weight and position and one non-reactive segment of controlled molecular weight and position;
wherein the reactive segments are positioned on either side of the central non-reactive segment on the polymer chain,
the reactive segments comprising copolymers derived from (i) one or more of the monomers of the non-reactive segment and (ii) at least one polymerizable comonomer comprising a crosslinkable functionality, the at least one polymerizable comononer comprising at least one monomer derived from the formula:
where R is H or CH 3 and X consists of a functional group capable of crosslinking,
wherein the functional group is a carboxyl group,
wherein the one or more monomers present in the non-reactive segment is the same type of monomer of the non-reactive segment present in the reactive segments,
wherein the one or more monomers of the non-reactive segment are present in the reactive segment in an amount effective for the reactive segments and the non-reactive segment to be molecularly miscible before cure,
wherein the non-reactive segment of the acrylic copolymer is derived from monomers selected from the group consisting of C 1 to about C 20 alkyl, aryl, or cyclic acrylates, C 1 to about C 20 alkyl, aryl, or cyclic methacrylates, or mixtures thereof.
2. The composition of claim 1 wherein the reactive segment comprises at least one monomer comprising the formula:
where R 3 is H or CH 3 and R 4 is a branched or unbranched, saturated alkyl group comprising 4 to 14 carbon atoms.
3. The composition of claim 1 wherein the reactive segment comprises an unsaturated carboxylic acid containing from 3 to about 20 carbon atoms.
4. The composition of claim 1 wherein the reactive segment comprises an acrylamide.
5. The composition of claim 1 wherein the position of the reactive segment and nonreactive segment are controlled by RAFT agent.
6. The composition of claim 1 wherein the average molecular weight (Mn) of the acrylic copolymer is in the range of about 10,000 g/mole to about 200,000 g/mole.
7. The composition of claim 1 wherein the acrylic copolymer has a polydispersity of less than 3.0.
8. A foam comprising the composition of claim 1 .
9. An elastomer comprising the composition of claim 1 .
10. A pressure sensitive adhesive comprising:
at least one acrylic copolymer comprising two reactive segments of controlled molecular weight and position and one non-reactive segment of controlled molecular weight and position;
wherein the reactive segments are positioned on either side of the central non-reactive segment on the polymer chain,
the reactive segments comprising copolymers derived from (i) one or more of the monomers of the non-reactive segment and (ii) at least one polymerizable comonomer comprising a crosslinkable functionality, the at least one polymerizable comononer comprising at least one monomer derived from the formula:
where R is H or CH 3 and X consists of a functional group capable of crosslinking,
wherein the functional group is a carboxyl group,
wherein the one or more monomers of the non-reactive segment are present in the reactive segment in an amount effective for the reactive segments and the non-reactive segment to be molecularly miscible before cure,
wherein the non-reactive segment of the acrylic copolymer is derived from monomers selected from the group consisting of C 1 to about C 20 alkyl, aryl, or cyclic acrylates, C 1 to about C 20 alkyl, aryl, or cyclic methacrylates, or mixtures thereof,
wherein the crosslinkable functional groups are crosslinked.
11. The pressure sensitive adhesive of claim 10 wherein the acrylic copolymer has a polydispersity of less than 3.0.
12. The pressure sensitive adhesive of claim 10 wherein the average molecular weight (Mn) of the acrylic copolymer is in the range of about 10,000 g/mole to about 200,000 g/mole.
13. The pressure sensitive adhesive of claim 10 wherein the one or more monomers present in the non-reactive segment is the same type of monomer of the non-reactive segment present in the reactive segments.
14. A method of preparing a pressure sensitive adhesive comprising the steps of:
polymerizing using a controlled radical polymerization process at least one monomer comprising at least one reactive functional group capable of undergoing a crosslinking reaction to form two reactive segments of controlled molecular weight and position;
polymerizing using a controlled radical polymerization process at least one monomer that is non-reactive with the reactive functional group of the reactive segments to form one non-reactive segment of controlled molecular weight and position;
forming an acrylic polymer from the reactive segments and the non-reactive segment;
crosslinking the acrylic polymer by mixing the acrylic polymer with an amount of a crosslinking agent;
wherein the one or more monomers of the non-reactive segment are present in the reactive segment in an amount effective for the reactive segments and the non-reactive segment to be molecularly miscible before cure,
wherein the reactive segments are positioned on either side of the central non-reactive segment on the polymer chain,
the reactive segments comprising copolymers derived from (i) one or more of the monomers of the non-reactive segment and (ii) at least one polymerizable comonomer comprising a crosslinkable functionality, the at least one polymerizable comononer comprising at least one monomer derived from the formula:
where R is H or CH 3 and X consists of a functional group capable of crosslinking,
wherein the functional group is a carboxyl group,
wherein the non-reactive segment of the acrylic copolymer is derived from monomers selected from the group consisting of C 1 to about C 20 alkyl, aryl, or cyclic acrylates, C 1 to about C 20 alkyl, aryl, or cyclic methacrylates, or mixtures thereof,
wherein the controlled radical polymerization process is stable free radical polymerization (SFRP).
15. The method of claim 14 wherein the reactive segment is polymerized first in the presence of a RAFT agent, the polymerization is terminated after the complete conversion of the at least one monomer comprising at least one reactive functional group to form the reactive segment(s).
16. The method of claim 14 wherein the non-reactive segment is polymerized first in the presence of a RAFT agent.
17. The method of claim 14 wherein the non-reactive segment is polymerized first in the presence of an SFRP agent.
18. The method of claim 14 wherein the reactive segment is polymerized first in the presence of an SFRP agent.
19. The method of claim 14 further comprising the step of crosslinking the functional groups of the reactive segment.