Control Over Controlled Radical Polymerization Processes

Abstract

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 . (canceled) 
     
     
         2 . A method of polymerizing unsaturated monomers, comprising:
 (a) mixing unsaturated monomers with an inactive metal catalyst, optionally ligand and an initiator having a transferable atom, wherein the inactive metal catalyst is present in the mixture at an amount of less than 250 ppm, on a mass basis relative to the total mixture;   (b) heating the mixture to a reaction temperature;   (c) adding a first portion of a non-activated reducing agent to the system to generate an activated reducing agent, wherein the non-activated reducing agent has a decomposition activation-dependent tin value of between 30 sec. and 30 min. at least one of the reaction conditions;   (d) reducing the inactive metal catalyst with the activated reducing agent to form an active metal catalyst;   (e) transferring the transferable atom with the active metal catalyst, thereby activating the initiator for unsaturated monomer addition; and   (f) adding at least a further portion of the non-activated reducing agent to the mixture to induce further polymerization of the unsaturated monomer;   
       wherein the at least further portion is added to the mixture at a point where at least 30 molar %, relative to the amount of unsaturated monomer introduced into the mixture, has been polymerized, and 
       wherein at least one polymer product has a degree of polymerization, with respect to the monomer residues corresponding to the unsaturated monomer, of at least 20 and the overall mixture has a conversion of at least 60 molar % relative to the amount of unsaturated monomer introduced into the mixture. 
     
     
         3 . A method of radical polymerization of an unsaturated monomer, comprising:
 (a) polymerizing an unsaturated monomer in a system comprising an initiator, optionally ligand and a metal catalyst at or above a reaction temperature;   (b) adding at a controlled rate a first amount of non-activated reducing agent to the system; and   (c) controlling the rate of polymerization of the unsaturated monomer by adding at a controlled rate a further amount of the non-activated reducing agent to the system at a point where at least 30 molar %, relative to the amount of unsaturated monomer introduced into the system, has been polymerized;   
       wherein at least one reaction condition is at or above a point suitable to trigger the decomposition of the non-activated reducing agent to form an active reducing agent. 
     
     
         4 . The method of  claim 3 , wherein the non-activated reducing agent has an activation-dependent t 1/2  value of between 30 sec. and 30 min. 
     
     
         5 . The method of  claim 3 , wherein the at least one reaction condition is temperature. 
     
     
         6 . The method of  claim 3 , wherein the at least one reaction condition includes electromagnetic energy. 
     
     
         7 . The method of  claim 3 , wherein the initiator is a halide-substituted alkyl initiator. 
     
     
         8 . The method of  claim 3 , wherein the metal catalyst is an inactive metal-halide catalyst. 
     
     
         9 . A method of making a polymer, comprising:
 (a) preparing a reaction mixture comprising a radically-polymerizable unsaturated monomer, an initiator, optionally ligand and an inactive metal catalyst in a molar ratio of the unsaturated monomer to the initiator of 25-5000:1 and a molar ratio of the catalyst to the initiator of 0.001 to 0.5:1 and the inactive metal catalyst is present in the mixture at an amount of less than 250 ppm, on a mass basis relative to the total mixture;   (b) heating the reaction mixture to a first temperature;   (c) disbursing a portion of a thermo-activated reducing agent into the heated reaction mixture;   (d) allowing a quantity of said portion of the thermo-activated reducing agent to decompose to an activated reducing agent;   (e) reducing a portion of the inactive metal catalyst with a portion of the activated reducing agent to form at least one active metal catalyst;   (f) activating one or more of the initiators with the at least one active metal catalyst to form one or more activated initiators;   (g) polymerizing at least one monomer in the presence of one or more activated initiators to extend a polymer chain; and   (h) repeating steps (c)-(g) while maintaining the temperature at or above a second temperature;   
       wherein the first and second temperatures are at or above a temperature wherein the thermo-activated reducing agent has a temperature-dependent t 1/2  value of between 30 sec. and 30 min. 
     
     
         10 . The method of  claim 9 , wherein the initiator is a halide-substituted alkyl initiator. 
     
     
         11 . The method of  claim 9 , wherein the inactive metal catalyst an inactive metal-halide catalyst. 
     
     
         12 . The method of  claim 9 , wherein steps (c)-(h) are conducted substantially continuously for a period of at least 2 hours. 
     
     
         13 . The method of  claim 9 , wherein the thermo-activated reducing agent is continuously being disbursed into the heated reaction mixture and the portion is adjusted periodically over the course of the polymerization reaction, relative to the molar conversion of unsaturated monomer. 
     
     
         14 . The method of  claim 9 , wherein the thermo-activated reducing agent is continuously being disbursed into the heated reaction mixture and the portion is adjusted periodically over the time course of the polymerization reaction, relative to the process parameters of temperature and viscosity. 
     
     
         15 . The method of  claim 9 , wherein the thermo-activated reducing agent is continuously being disbursed into the heated reaction mixture and the portion is adjusted periodically over the course of the polymerization reaction, relative to the molar conversion of unsaturated monomer, over an interval of time, wherein the interval of time is greater than 3 minutes. 
     
     
         16 . The method of  claim 9 , wherein the non-activated reducing agent is not added until at least 60 molar % conversion of the unsaturated monomer is achieved, relative to the molar amount of unsaturated monomer. 
     
     
         17 . The method of  claim 9 , wherein said second temperature is at least 10 degrees hotter than said first temperature. 
     
     
         18 . The method of  claim 9 , wherein the polymerization reaction is an ARGET ATRP reaction. 
     
     
         19 . The method of  claim 9 , wherein the polymerization reaction is an ICAR ARGET ATRP reaction. 
     
     
         20 . The method of  claim 9 , wherein the polymerization reaction is conducted at a temperature within 15 degrees celsius below the boiling point of the unsaturated monomer.