Compartmentalization refers to the physical confinement of reactants within discrete confined spaces, so called nanoreactors (Zetterlund 2011). In the field of radical polymerization, by nanoreactors one normally refers to monomer droplets, monomer-swollen micelles or polymer particles with diameters lower than approximately 200 nm during polymerization in dispersed systems (emulsion, miniemulsion etc.; Zetterlund et al., 2008). Compartmentalization effects in radical polymerization become significant if some fraction of droplets/particles contain a sufficiently low number of the relevant reactant(s). The concept of compartmentalization and the use of nanoreactors are also being exploited in other areas of chemistry (Monteiro 2010).
The last two decades have seen the development of a range of techniques of controlled/living radical polymerization (CLRP), which enable precise polymer synthesis, good control over molecular weight distributions (MWDs) and makes various complex polymer architectures accessible (Zetterlund et al. 2008). CLRP systems based on the so called persistent radical effect can be influenced by compartmentalization via (a) the segregation effect and (b) the confined space effect (Fig. 1; Zetterlund and Okubo 2006; Zetterlund 2011). The segregation effect refers to two species located in separate particles being unable to react. The confined space effect refers to two species located in the same particle reacting at a higher rate in a small particle than in a large particle. In CLRP, the segregation effect can lead to a lower rate of bimolecular termination between propagating radicals, and thus higher end-functionality. The confined space effect may result in a higher rate of deactivation, and thus better control over the MWD.
This presentation will provide a brief overview of compartmentalization effects in CLRP in dispersed systems, and outline how such effects can be exploited to improve both the end-functionality and the level of control over the MWD.