Supramolecular Multiblock Polystyrene-Polyisobutylene Copolymers via Ionic Interactions
Main-chain supramolecular block copolymers consist of individual blocks that are connected by non-covalent bonds. The work described here used ionic interactions as the non-covalent linkers, which provided much stronger binding energy compared to more commonly used hydrogen bonds. Two oligomeric building blocks, i.e. telechelic polystyrene end-capped with sulfonic acid (PS(SO3)2, Mn=6500Da, PDI=1.19) and telechelic polyisobutylene end-capped with primary amine (PIB(NH2)2, Mn=6200Da, PDI=1.02), were employed to prepare supramolecular multiblock copolymers (SMBCP). The SMBCP was a clear, flexible and self-standing film with a highly ordered microstructure of lamellar nanodomains, as determined by small-angle X-ray scattering (SAXS) and frequency-dependent melt rheology. An order-disorder transition (ODT) was observed using temperature dependent SAXS. Temperature sweep rheological measurements showed a plateau and ODT, which again demonstrated the formation of the high molecular weight SMBCP. The nonlinear response of the SMBCP was investigated by three strain sweep-time sweep cycles. Due to the high dissociation energy of the ionic interactions used, the supramolecular block copolymers remained intact even when large strain amplitude was applied.