Control over reverse addition fragmentation transfer polymerization processes
A procedure for improved temperature control in controlled radical polymerization processes is disclosed. The procedure is directed at controlling the concentration of the persistent radical in ATRP and NMP polymerizations procedures and the concentration of radicals in a RAFT polymerization process by feeding a reducing agent or radical precursor continuously or intermittently to the reaction medium through one of more ports.
1. A RAFT polymerization process, comprising:
a) forming a polymerization mixture, comprising:
i) at least a first free-radically polymerizable compound; and
ii) a RAFT agent;
b) minimizing uncontrolled exothermic reactions during the polymerization process by:
1) initiating RAFT polymerization by adding an initial amount of a free-radical initiator at a first temperature to the polymerization mixture to generate activated RAFT agents; and
2) adding further amounts of the free-radical initiator at a controlled rate of addition to the polymerization mixture to generate or regenerate activated RAFT agents.
2. The process of claim 1 , wherein the RAFT agent is one or more dithioesters.
3. The process of claim 1 , wherein the controlled rate of addition controls the polymerization rate of the polymerization process.
4. The process of claim 1 , wherein the controlled rate of addition controls the temperature of the polymerization process.
5. The process of claim 1 , wherein the controlled rate of addition controls instantaneous concentrations of radicals in the polymerization process.
6. The process of claim 1 , wherein the controlled rate of addition:
a) controls propagation of polymeric chains formed in the polymerization mixture;
b) maintains the polymerization mixture at or above the first temperature;
c) allows conversion of the at least first free-radically polymerizable compound to exceed 80% conversion; or
d) combinations thereof.
7. The process of claim 1 , wherein the controlled rate of addition is continuously or intermittently adjusted, or combinations thereof.
8. The process of claim 1 , wherein the controlled rate of addition is continuously or intermittently adjusted, or combinations thereof, to maintain a targeted rate of polymerization.
9. The process of claim 1 , wherein the controlled rate of addition is continuously or intermittently adjusted, or combinations thereof, to maintain a targeted polymerization temperature.
10. The process of claim 1 , wherein the free radical initiator is 2,2′-azobis(2-methylpropionitrile) (AIBN) or 2,2′-azobis(4-methoxy-2.4-dimethyl valeronitrile) (V-70).
11. The process of claim 1 , wherein the free radical initiator is a photoresponsive radical initiator.
12. The process of claim 1 , wherein the polymerization process allows conversion of the at least first free-radically polymerizable compound to exceed 80% conversion.
13. The process of claim 1 , wherein the at least first free-radically polymerizable compound is an unsaturated monomer.
14. The process of claim 1 , wherein the at least first free-radically polymerizable compound comprises styrene, n-butyl acrylate, methacrylate, or methyl methacrylate.
15. The process of claim 1 , wherein the polymerization process is conducted in a bulk polymerization process; is performed in the presence of a solvent; is conducted from solid surfaces; or is conducted in a biphasic polymerization process, an emulsion polymerization process, a mini-emulsion polymerization process, a microemulsion polymerization process, a reverse emulsion polymerization process, or a suspension polymerization process.
16. The process of claim 1 , wherein the resulting polymer is a linear polymer or copolymer, a branched polymer or copolymer, a block copolymer, a brush polymer or copolymer, a star polymer or copolymer, or a star macromolecule.
17. The process of claim 1 , wherein the polymerization process further comprises adding one or more further amounts of the at least first free-radically polymerizable compound.
18. The process of claim 1 , wherein the polymerization process further comprises:
a) polymerizing at least a second free-radically polymerizable compound at a second polymerizing temperature;
b) polymerizing a plurality of free-radically polymerizable compounds at a corresponding plurality of polymerizing temperatures;
c) cross-linking the polymerization mixture at a cross-linking temperature; or
d) combinations thereof.
19. The process of claim 1 , wherein the polymerization process is conducted in an industrial scale system.
20. A RAFT polymerization process, comprising:
a) forming a polymerization mixture, comprising:
i) at least a first free-radically polymerizable compound; and
ii) a RAFT agent;
b) minimizing uncontrolled exothermic reactions during the polymerization process by:
1) initiating RAFT polymerization by adding an initial amount of a free-radical initiator at a first temperature to the polymerization mixture to generate activated RAFT agents; and
2) adding further amounts of the free-radical initiator at a controlled rate of addition to the polymerization mixture to generate or regenerate activated RAFT agents, wherein the controlled rate of addition is adjusted to be commensurate with rate of radical-radical termination reactions.
21. The process of claim 20 , wherein the RAFT agent is one or more dithioesters.
22. The process of claim 20 , wherein the controlled rate of addition controls the polymerization rate of the polymerization process.
23. The process of claim 20 , wherein the controlled rate of addition controls the temperature of the polymerization process.
24. The process of claim 20 , wherein the controlled rate of addition controls instantaneous concentrations of radicals in the polymerization process.
25. The process of claim 20 , wherein the polymerization process allows conversion of the at least first free-radically polymerizable compound to exceed 80% conversion.
26. The process of claim 20 , wherein the controlled rate of addition is continuously adjusted.
27. The process of claim 20 , wherein the controlled rate of addition is intermittently adjusted.
28. The process of claim 20 , wherein the polymerization process is conducted in an industrial scale system.