Polymerization induced self-assembly: tuning of nano-object morphology by use of CO2

Abstract

Polymeric nano-objects of non-spherical morphology (e.g. rods, vesicles) have a range of potential applications, and it is thus of great interest to develop synthetic approaches that enable large scale production as well as fine tuning of the morphology. To this end, we have developed reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization in an alcoholic medium pressurized to low pressure (8.0 MPa) with CO₂. It is demonstrated that the presence of CO₂ has a profound effect on the morphology of the resulting polymer aggregates. In the presence of CO₂, the formation of nano-objects with a high interfacial core/corona curvature is favoured relative to the corresponding system without CO₂, e.g. rods are formed (with CO₂) under conditions where vesicles (no CO₂) would otherwise form. This is a convenient method for tuning the morphology without altering the recipe, and represents an attractive route to pure rod morphology, which is typically somewhat elusive.