Creation of micropores by RAFT copolymerization of conjugated multi-vinyl cross-linkers
We report a new methodology that allows for forming micropores in hierarchically porous polymers by employing the reversible addition–fragmentation chain transfer (RAFT) copolymerization of conjugated multi-vinyl cross-linkers with styrene. Using divinylbenzene, 4,4′-divinylbiphenyl, 1,3,5-tris(4-vinylphenyl)benzene and tetrakis(4-vinylbiphenyl)methane as cross-linkers, the RAFT copolymerization was carried out in the presence of polylactide macro-chain transfer agents. During the polymerization, microphase separation occurred spontaneously to produce cross-linked block polymer precursors with a bicontinuous morphology composed of polylactide and cross-linked polystyrene microdomains. Hierarchically porous polymers with strong fluorescence were successfully derived by polylactide etching. We demonstrate that the rigid conjugated structure of the cross-linkers with a high cross-linking density is critical for creating the micropores and for stabilizing the mesopores that are templated by the polylactide domain.