Polymerization behaviors and branching structural analysis of branched polymers in self-condensing atom transfer radical copolymerization of different inimers

The investigation of the relationship between the structure and properties of branched polymers heavily relies on the branched morphology. In this study, we explored the electron-rich and electron-poor effects that arise from different types of double bonds in inimers using self-condensing atom transfer radical polymerization (ATRP). A comparative analysis of polymerization systems using various inimers as branching monomers revealed notable differences. Specifically, when examining styrene-based initiator (St-inimer) systems, the absence of a discernible nucleation feature and the non-conformance to the “core-first-arm-later” method for synthesizing star-shaped polystyrene (branching morphology factor ε is higher than 1.0) were observed. On the other hand, the methacrylate-based initiator (MA-inimer) systems exhibited a clear nucleation process during polymerization, followed by linear molecular weight growth and a constant polydispersity characteristic, consistent with the “core-first-arm-later” approach for synthesizing star-shaped polystyrene (ε is about 0.6, lower than 1.0). The maleimide-based initiator (Mal-inimer) systems demonstrated an initial nucleation phase, a mid-stage linear growth phase with a constant polydispersity characteristic, and a late-stage nonlinear growth phase resulting in a broader polydispersity index. As a result, the polymerization process in maleimide-based initiator systems conforms to the law of preparing star branched polymers with multi-core structures (ε is about 0.8).