Microstructure and Solvent Distribution in Cross-Linked Diblock Copolymer Gels

Gels were created by irradiating poly(α-methylstyrene-block-isoprene) (PaMS−I) and poly(vinylferrocenium triflate-block-isoprene) (PVFT−I) copolymers with an electron beam and swelling the resulting cross-linked solids in good solvents. The radiation cross-links the polyisoprene (PI) block, induces chain scission of the poly(α-methylstyrene) block (PaMS), and has no effect on the poly(vinylferrocenium triflate) (PVTF) block. After extraction of un-cross-linked chains, the PaMS−I gels comprise solvent-filled, open channels inside a swollen PI network, while the swollen PVFT−I gels comprise channels of solvated PVFT chains inside a swollen PI network. The dependence of the structure, composition, and cross-linking density of the swollen microphases on radiation dose is determined by combining small-angle neutron scattering experiments with conventional gel characterization methods.