In this work, by combining size exclusion chromatography (SEC) and liquid chromatography at the critical condition (LCCC) techniques, we have studied the multimer cyclization effect during click step-growth polymerization of AB-type macromonomers. First, by atom transfer radical polymerization (ATRP), we have synthesized a series of alkynyl and azide functional AB-type polystyrene macromonomers with different molar masses, i.e., PS n . Second, via the click step-growth polymerization of a PS n macromonomer in dimethylformamide (DMF) at varied reaction concentrations (Cs), we have prepared polyaddition products [(PS n ) m ] with large polydispersity indices, where m represents the average degree of polymerization of the macromonomer. Further, narrowly distributed fractions have been obtained by SEC fractionation. Third, we have quantitatively analyzed how the macromonomer molar mass, reaction concentration, and multimer molar mass influence the percentage of a cyclic topoisomer (wtcyclic) for (PS n ) m samples. In particular, we have established the relation between wtcyclic and C for unfractionated (PS n ) m , i.e., wtcyclic = 0.86–0.32 log C, and the relation between wtcyclic and m for fractionated (PS n ) m prepared at a constant C = 100 g/L, i.e., log wtcyclic = −0.46m + 0.16. For the first time, our result has unambiguously pointed out that neither a cyclic topoisomer nor a linear topoisomer can be ignored when considering the structure–property quantitative relationship for polyaddition products.

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