Commercial Viability of the Living-Radical Polymerization Processes

6 Commercial Viability of the Living-Radical Polymerization Processes 

The success of the living-radical polymerization field will be defined on the basis of the commercialization of any of these processes [48], It is believed that the strength of the living-radical polymerization systems lies in their ability to make polymers of novel architecture, for example, block copolymers. However, very little work has been done to look at the properties of materials prepared by these processes. It remains to be seen whether block copolymers, prepared by living-radical polymerization processes, have any performance advantages over random copolymers prepared by conventional free-radical polymerization. 

Conversion is also an issue in that it is very difficult to go to conversions above 80% in bulk primarily because of the high viscosity of the reaction medium. Miniemulsions can readily be taken to 99.5% conversion, and this has been accomplished in the SFRP and RAFT processes, but it is still an open question as to how living the system is at these high conversions. All systems report the ability to perform the polymerizations in solution, but certainly in the case of SFRP broader polydispersities result, probably due to chain transfer to solvent. 

The cost of a material is a major factor in any decision to move ahead with commercialization. Any added reagent or extra process step that is required in any of these processes will inevitably add to the cost of the material. In the case of the SFRP process, the cost of the nitroxides is variable from relatively inexpensive (12-15 /kg) for hydroxyTEMPO to very expensive (hundreds of dollars per kilogram) for custom-synthesized nitroxides. The use of an expensive nitroxide does not preclude the use of SFRP, but restricts it to high-value-added applications. Also, the amount of nitroxide that will be used will vary according to the molecular weight of the polymer that is desired. 

For the ATRP process, the cost of the ligands associated with the metals can be costly, so judicious choice of ligands will be necessary if the polymer is to be used in 

---