Construction of Robust Cross-Linked Polymer Shells in Interfacial Photocycloaddition Polymerization: Trifunctional vs Tetrafunctional Monomers

Interfacial photocycloaddition polymerization (IPCP) has emerged as an effective strategy for the synthesis of degradable polymer capsules. In this process, photocycloaddition between multifunctional photoreactive monomers occurs exclusively at the particle interface, while unreacted monomers in the core region can subsequently be exchanged with target encapsulation molecules. In this study, we investigated how the number of photoreactive groups in monomer species influences the formation of cross-linked polymer shells in IPCP, using tri- and tetrafunctional monomers. The tetrafunctional monomer significantly accelerated the development of a robust capsule shell compared with its trifunctional counterpart. Hollow polymer particles impermeable to low-molecular-weight compounds were obtained after a substantially shorter photoirradiation period (6 h) with the tetrafunctional monomer than with the trifunctional monomer (20 h), despite both systems exhibiting comparable conversions of photoreactive groups. These findings demonstrate that the addition of a single photoreactive group can markedly enhance the efficiency of robust shell construction in IPCP.