Molecular Weight Development of Surface and Solution Polymers in Surface‐Initiated Atom Transfer Radical Polymerization and Their Dependence on Radical Termination Modes

In the surface-initiated atom transfer radical polymerization, the polymerization proceeds both in solution and on surface. This work reports a modeling study, describing the growth of the molecular weight and polydispersity of polymer both on surface and in solution. It is found that both surface radical termination and solution monomer consumption significantly suppress the growth rate of polymer layer. Besides, the former affects the molecular weights of polymer both on surface and in solution. If the termination rate constant in solution (k(t,sol-sol)) is the same as that of surface and solution interfaces (k(t,sol-surf)), and the surface termination (k(t,surf-surf)) is negligible, then the polymers both on surface and in solution have the same molecular weight. However, if surface radicals terminate among themselves, the molecular weight of polymer on surface will lower than that in solution. Such termination is promoted by surface radical migration through activation/deactivation reactions in solution. When k(t,sol-surf) < k(t,sol-sol), the molecular weight of surface polymer becomes higher than that in solution. This situation is resulted from surface radical trap due to a high grafting density.