Coarse‐Grained Simulation Study on Gradient‐Free Radical Polymerization via a Beer's Law‐Based Heterogeneous Initiation Model

Gradient polymer materials exhibit great potential for applications in fields such as sensors and biomedicine. While photoinitiated radical polymerization represents a common strategy for gradient fabrication, mesoscopic insights into polymerization kinetics and topological evolution under the control of gradient initiation—similar to photoinitiation—remain limited. In this study, using CGMD simulations, we developed a radical polymerization model incorporating a space‐dependent initiation rate inspired by the mathematical form of Beer's Law. This model was utilized to investigate the reaction kinetics, topological features, and mechanical responses of radical polymerization under a decaying initiation reaction. The results indicate that the decay of the initiation reaction induces spatio‐temporal discrepancies in the reactions within the system. In highly graded systems, small clusters preferentially form and merge in the high‐initiation region, whereas the low‐initiation region exhibits a pronounced reaction lag due to kinetic inhibition, ultimately yielding a gradient distribution of particles and crosslinkers. Under this kinetic heterogeneity, the fraction of “bridges” (elastically effective chains) decreases in the top region but increases in the bottom region due to prolonged free‐radical lifetimes, thereby optimizing the overall topological structure. Mechanical analysis confirms that the initiation decay marginally enhances the overall mechanical performance while reallocating the stress‐bearing capacity toward the high‐initiation region.