Supramolecular Multiblock Polystyrene-Polyisobutylene Copolymers via Ionic Interactions

A supramolecular multiblock copolymer was synthesized by mixing two telechelic oligomers, alpha,omega-sulfonated polystyrene, HO3S-PS-SO3H, derived from a polymer prepared by RAFT polymerization, and alpha,omega-amino-polyisobutylene, H2N-PIB-NH2, prepared by cationic polymerization. During solvent casting, proton transfer from the sulfonic acid to the amine formed ionic bonds that produced a multiblock copolymer that formed freestanding flexible films with a modulus of 90 MPa, a yield point at 4% strain and a strain energy density of 15 MJ/m(3). Small angle X-ray scattering characterization showed a lamellar morphology, whose domain spacing was consistent with the formation of a multiblock copolymer based on comparison to the chain dimensions. A reversible order-disorder transition occurred between 190 and 210 degrees C, but the sulfonic acid and amine functional groups were observed to decompose at those elevated temperatures based on companion optical microscopy and spectroscopy measurements. For high nonlinear strains, the dynamic modulus, G', decreased by nearly an order of magnitude and the loss modulus, G '', decreased by a factor of 1.4, but both recovered to their original values once the strain was reduced to within the linear response region.