Evaluation of Ring Expansion-Controlled Radical Polymerization System by AFM Observation

We here present a direct link between the reaction mechanisms for the ring-expansion “vinyl” polymerization system and atomic force microscopy (AFM) observations. The brush-modification clearly discriminates the desired cyclic species with the contour lengths (L c) of 28–132 nm and molar masses (M AFM) of 60.2–283 kg mol–1 from the other linear ones. The 293 polymer blushes observed in a 1.0 μm × 1.0 μm AFM image are individually characterized, eventually providing clear answers about the mechanisms of this rare polymerization system, which include ring-expansion vinyl polymerizations to generate cyclic polymers, fusions of the generated cycles to form multimers, and their scission to form linear or ring-opened species. The relationship between the molecular chain lengths and the cyclic versus linear morphologies is highlighted.