Control over controlled radical 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 polymerization process, comprising:
i) introducing one or more free radically polymerizable monomers into a system initially comprising:
a) at least one transition metal catalyst; and
b) an atom transfer radical polymerization initiator; and
ii) polymerizing the one or more free radically polymerizable monomers by feeding a free radical initiator into the system to regenerate the at least one transition metal catalyst at a controlled rate to minimize uncontrolled polymerization reactions;
wherein the molar ratio of the at least one transition metal catalyst to the atom transfer radical polymerization initiator is less than 0.10.
2. The polymerization process of claim 1 , wherein the free radical initiator is continuously or intermittently fed into the system.
3. The polymerization process of claim 1 , wherein the at least one transition metal catalyst is introduced into the system in a high or an oxidatively stable oxidation state.
4. The polymerization process of claim 3 , wherein the free radical initiator reduces the concentration of the higher oxidation state transition metal present in the system.
5. The polymerization process of claim 1 , wherein the free radical initiator reacts with a higher oxidation state transition metal complex of the at least one transition metal catalyst in a non-radical forming reaction.
6. The polymerization process of claim 1 , wherein the free radical initiator reacts with a higher oxidation state transition metal complex of the at least one transition metal catalyst in a non-ATRP initiator forming reaction.
7. The polymerization process of claim 1 , wherein the free radical initiator is a photoresponsive radical initiator.
8. The polymerization process of claim 1 , wherein the process is a bulk polymerization process, a biphasic polymerization process, an emulsion polymerization process, a reverse emulsion polymerization process, or a suspension polymerization process.
9. The polymerization 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).
10. The polymerization process of claim 1 , wherein the feeding rate of the free radical initiator is continuously or intermittently adjusted to allow conversion of the one or more polymerizable monomers to polymer to exceed 80%.
11. The polymerization process of claim 1 , wherein the feeding rate of the free radical initiator is continuously or intermittently adjusted to maintain a targeted rate of polymerization.
12. The polymerization process of claim 1 , wherein the feeding rate of the free radical initiator is continuously or intermittently adjusted to maintain a targeted temperature of the reaction.
13. The polymerization process of claim 1 , wherein the one or more polymerizable monomers comprises styrene, n-butyl acrylate, or methyl methacrylate.
14. The polymerization process of claim 1 , wherein the transition metal of the at least one transition metal catalyst is copper.
15. The polymerization process of claim 14 , wherein the copper is present in an initial amount of at least 10 ppm.
16. The polymerization process of claim 1 , wherein the at least one transition metal catalyst is CuBr 2 .
17. The polymerization process of claim 1 , wherein the atom transfer radical polymerization initiator is diethyl 2-bromo-2-methylmalonate (DEBMM) or 2-bromopropionitrile (BrPN).
18. The polymerization process of claim 1 , wherein the polymerization process is conducted at a temperature of 45° C. to 110° C.
19. The polymerization process of claim 1 , wherein the polymerization process is a CRP process, an ICAR ATRP process, an ARGET ATRP process, a RAFT process, or an NMP process.