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:
polymerizing free radically (co)polymerizable monomers in the presence of a reducing agent and a polymerization medium initially comprising:
at least one transition metal catalyst; and
an atom transfer radical polymerization initiator; and
wherein:
i) the molar ratio of the transition metal catalyst to the atom transfer radical polymerization initiator is less than 0.10; and
ii) the reducing agent is continuously added to regenerate the at least one transition metal catalyst at a rate commensurate with the rate of radical-radical termination reactions.
2. The polymerization process of claim 1 , wherein the reducing agent is a free radical initiator.
3. The polymerization process of claim 2 , wherein the free radical initiator comprises 2,2′-azobis(2-methylpropionitrile (AIBN) or 2,2′-azobis(4-methoxy-2.4-dimethyl valeronitrile) (V-70).
4. The polymerization process of claim 2 , wherein the rate of addition of the free radical initiator is continuously adjusted to allow the conversion of the (co)polymerizable monomers to polymer to exceed 90%.
5. The polymerization process of claim 2 , wherein the rate of addition of the free radical initiator is continuously adjusted to allow the conversion of the (co)polymerizable monomers to polymer to exceed 95%.
6. The polymerization process of claim 2 , wherein the rate of addition of the free radical initiator is continuously adjusted to allow the conversion of the (co)polymerizable monomers to polymer to exceed 99%.
7. The polymerization process of claim 2 , wherein the rate of addition of the free radical initiator is continuously adjusted to maintain a targeted rate of polymerization.
8. The polymerization process of claim 2 , wherein the rate of continuously adding the free radical initiator maintains a targeted temperature of the reaction.
9. The polymerization process of claim 1 , wherein the reducing agent reacts with the higher oxidation state transition metal complex of the at least one transition metal catalyst in a non-radical forming, and a non-ATRP initiator, forming reaction.
10. The polymerization process of claim 9 , wherein the reducing agent comprises a stable organic molecule including sulfites, bisulfites, thiosulfites, mercaptans, hydroxylamines, amines, hydrazine (N 2 H 4 ), phenylhydrazine (PhNHNH 2 ), hydrazones, hydroquinone, food preservatives, flavonoids, beta carotene, vitamin A, α-tocopherols, vitamin E, propyl gallate, octyl gallate, propionic acids, ascorbic acid, sorbates, reducing sugars, sugars comprising an aldehyde group, glucose, lactose, fructose, dextrose, potassium tartrate, nitrites, dextrin, aldehydes, glycine, or antioxidants.
11. The polymerization process of claim 9 , wherein the reducing agent reduces the concentration of the higher oxidation state transition metal formed by radical-radical termination reactions to a concentration close to the concentration present in the system after the addition of the immediately previous addition of the reducing agent.
12. The polymerization process of claim 1 , wherein the reducing agent is a photoresponsive radical initiator; and
wherein a fraction of the added photoresponsive radical initiator is periodically decomposed by a pulse of light wherein the intensity and duration of the photo-stimulation is commensurate with the moles of radical-radical termination reactions that occurred since the immediately previous pulse of light.
13. The polymerization process of claim 1 , wherein the polymerization 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.
14. The polymerization process of claim 1 , wherein the (co)polymerizable monomers comprise styrene, n-butyl acrylate, or methyl methacrylate.
15. The polymerization process of claim 1 , wherein the transition metal of the at least one transition metal catalyst comprises copper.
16. The polymerization process of claim 15 , wherein the copper is present in an initial amount of 50 ppm.
17. The polymerization process of claim 15 , wherein the copper is present in an initial amount of 10 ppm.
18. The polymerization process of claim 15 , wherein the at least one transition metal catalyst is CuBr 2 .
19. The polymerization process of claim 1 , wherein the atom transfer radical polymerization initiator comprises diethyl 2-bromo-2-methylmalonate(DEBMM) or 2-bromopropionitrile (BrPN).
20. The polymerization process of claim 1 , wherein the polymerization process is conducted at a temperature of 45° C. to 110° C.