Beyond Simple AB Diblock Copolymers: Application of Bifunctional and Trifunctional RAFT Agents to PISA in Water

The influence of the macromolecular reversible addition-fragmentation chain transfer (macro-RAFT) agent architecture on the morphology of the self-assemblies obtained by aqueous RAFT dispersion polymerization in polymerization-induced self-assembly (PISA) is studied by comparing amphiphilic AB diblock, (AB)(2) triblock, and triarm star-shaped (AB)(3) copolymers, constituted of N,N-dimethylacrylamide (DMAc = A) and diacetone acrylamide (DAAm = B). Symmetrical triarm (AB)(3) copolymers could be synthesized for the first time in a PISA process. Spheres and higher order morphologies, such as worms or vesicles, could be obtained for all types of architectures and the parameters that determine their formation have been studied. In particular, we found that the total DPn of the PDMAc and the PDAAm segments, i.e., the same overall molar mass, at the same M-n(PDMAc)/M-n(PDAAm) ratio, rather than the individual length of the arms determined the morphologies for the linear (AB)(2) and star shaped (AB)(3) copolymers obtained by using the bi- and trifunctional macro-RAFT agents.