Compartmentalization in Atom Transfer Radical Polymerization (ATRP) in Dispersed Systems

Summary: Compartmentalization in atom transfer radical polymerization (ATRP) in dispersed systems at low conversion (<10%) has been investigated by means of a modified Smith–Ewart equation focusing on the system n ‐butyl acrylate/CuBr/4,4′‐dinonyl‐2,2′‐dipyridyl at 110 °C. Compartmentalization of both propagating radicals and deactivator was accounted for in the simulations. As the particle diameter ( d ) decreases below 70 nm, the polymerization rate ( R p ) at 10% conversion increases relative to the corresponding bulk system, goes through a maximum at 60 nm, and thereafter decreases dramatically as d decreases further. This behavior is caused by the separate effects of compartmentalization (segregation and confined space effects) on bimolecular termination and deactivation. The very low R p for small particles ( d  < 30 nm) is due to the pseudo first‐order deactivation rate coefficient being proportional to d −3 .Simulated propagating radical concentration ([P•]) as a function of particle diameter ( d ) at 10% conversion for ATRP of n ‐butyl acrylate ([ n BA] 0  = 7.1 M , [PBr] 0  = [CuBr/dNbpy] 0  = 35.5 m M ) in a dispersed system at 110 °C. The dotted line indicates the simulated [P•] in bulk at 10% conversion.