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 RAFT polymerization process, comprising:
i) initiating RAFT polymerization by adding a reducing agent to a RAFT polymerization mixture comprising a RAFT agent and at least a first free-radically polymerizable compound; and
ii) mitigating uncontrolled polymerization reactions during the RAFT polymerization process by adding further amounts of the reducing agent at a controlled rate of addition to generate or regenerate the activated RAFT agent; and
wherein the reducing agent is added at polymerization conditions at which the reducing agent has an activation-dependent t 1/2 value of between 30 sec. and 30 min; and
wherein the controlled rate of addition is adjusted to maintain the polymerization conditions at which the reducing agent has an activation-dependent t 1/2 value of between 30 sec. and 30 min.
2. The RAFT polymerization process of claim 1 , wherein the controlled rate of addition further controls: i) the rate of polymerization of the RAFT polymerization process; or ii) the temperature of the RAFT polymerization process.
3. The RAFT polymerization process of claim 1 , wherein the controlled rate of addition:
a) controls propagation of polymeric chains formed in the RAFT polymerization mixture;
b) maintains the RAFT polymerization mixture at a targeted rate of polymerization;
c) maintains the RAFT polymerization mixture at a targeted polymerization temperature;
d) allows conversion of the at least first free-radically polymerizable compound to exceed 80% conversion;
e) reduces the termination of RAFT polymerization; or
f) a combination thereof.
4. The RAFT polymerization process of claim 1 , wherein the controlled rate of addition is adjusted continuously or intermittently to maintain one or more of the targeted rate of polymerization and the targeted polymerization temperature.
5. The RAFT polymerization process of claim 1 , wherein the controlled rate of addition comprises one or more of a continuous addition, an intermittent addition, or an adjustable addition.
6. The RAFT polymerization process of claim 1 , wherein the reducing agent comprises an activated reducing agent, a non-activated reducing agent, or a combination thereof.
7. The RAFT polymerization process of claim 6 , wherein the activated reducing agent comprises a radical species generated from the decomposition of azo-containing compound, a peroxide compound, a peroxy acid, or a combinations thereof.
8. The RAFT polymerization process of claim 6 , wherein the non-activated reducing agent comprises one or more of an azo-containing compound, a peroxide compound, and a peroxy acid.
9. The RAFT polymerization process of claim 1 , wherein the reducing agent comprises one or more of: 2,2′-azobis(2-methylpropionitrile) (MEM); a peroxide; a peroxy acid; tert-butyl peracetate; 1,1-bis(tert-butylperoxy)-3,3,5-(dibutylphthalate)trimethylcyclohexane; 2,2′-azobis(4-methoxy-2.4-dimethyl valeronitrile) (V-70); 2,2′-azobis(2,4-dimethylvaleronitrile) (V-65); dimethyl 2,2′-azobis(2-methylpropionate) (V-601); 2,2′-azobis(2-methylbutyronitrile) (V-59); 1,1′-azobis(cyclohexane-1-carbonitrile) (V-40); or 2,2′-azobis[N-(2-propenyl)-2-methylpropionamide] (VF-096).
10. The RAFT polymerization process of claim 1 , wherein the at least first free-radically polymerizable compound comprises an unsaturated monomer.
11. The RAFT polymerization process of claim 10 , wherein the unsaturated monomer is a hydrophilic unsaturated monomer.
12. The RAFT polymerization process of claim 10 , wherein the unsaturated monomer is a hydrophobic unsaturated monomer.
13. The RAFT polymerization process of claim 1 , wherein the RAFT agent comprises a dithioester.
14. The RAFT polymerization process of claim 1 , wherein the RAFT polymerization process is:
a) conducted in a bulk polymerization process;
b) performed in the presence of a solvent;
c) is conducted from solid surfaces; or
d) a combination thereof.
15. The RAFT polymerization process of claim 1 is conducted in one or more of 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 RAFT polymerization 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 RAFT polymerization process of claim 1 , wherein uncontrolled exothermic reactions are mitigated in intensity, duration, or frequency during the RAFT polymerization process.
18. The RAFT polymerization process of claim 1 allows conversion of the at least first free-radically polymerization compound to exceed about 90%, or greater, conversion.