Blends of oppositely charged polymers are capable of self-assembling into well-ordered nanostructures via supramolecular self-assembly. A series of monosulfonated-terminated polystyrene (PS) and monopiperidine–terminated poly(dimethylsiloxane) (PDMS) polymers with different molecular weights were synthesized and blended to investigate their phase behavior. A new synthetic route for piperidine-terminated PDMS with low dispersity and high end-group fidelity was developed based on a functionalized initiator accessible from commercially available reagents and compatible with anionic ring-opening polymerization. The resulting nanostructure of the blends was measured via small-angle X-ray scattering (SAXS) performed across a range of temperatures and revealed disordered structures in blends prepared with low molecular weight polymers. A model derived by Tanaka using the random phase approximation (RPA) was applied to extract the heteroassociation fraction (z) and effective interaction parameter (χeff), and a quantitatively similar value of z was observed across all blends with disordered morphologies. High molecular weight blends exhibited a variety of hybrid ordered nanostructures, and by precisely tuning the mixing ratio, we were able to induce phase transitions and achieve a variety of ordered nanostructures with long-range order. A molecular-scale mechanism to balance the electrostatic strength of end group association and segregation strength between the constituent polymers is proposed to rationalize the observed phase behavior.
Qin et al. (2026) studied this question.