Electrostatic tuning of block copolymer morphologies by inorganic macroions

- A facile strategy to tune block copolymer morphologies is presented by using polyoxometalate macroions as electrostatic additives.
- Polyoxometalate macroions can interrupt the regularity of PS-b-P4VP to form disordered bicontinuous morphologies.
- The incorporated polyoxometalate macroions can tune the thermal and viscoelastic properties of PS-b-P4VP.

Bicontinuous block copolymer morphologies can offer unique transporting properties in catalysis and energy materials, whereas they are difficult to be obtained due to the relatively narrow window in phase diagram. In this work, we present a facile strategy to induce block copolymers to form bicontinuous morphologies by using nanoscale ionic clusters as electrostatic additives. A Keggin-type polyoxometalate cluster, H4SiW12O40 (SiW) was incorporated into the matrices of a series of poly(styrene-b-4-vinylprydine) (PS-b-P4VP) through the electrostatic interaction between SiW and P4VP chains. Upon the increase of SiW content, disordered bicontinuous morphologies were evolved from the PS-b-P4VP with an initial cylindrical phase, accompanying with the disappeared Tg of P4VP and the mechanical reinforcement of PS-b-P4VP/SiW nanocomposites. The bicontinuous structures can also be induced by other polyoxometalate clusters with different charges. However, the PS-b-P4VP with an initial isolating spherical phase retains their spherical structures in spite of loading SiW. These results demonstrate a new concept to obtain bicontinuous polymeric structures by using inorganic macroions to interrupt the regularity of percolating block copolymer phase, which may favor the fabrication of transporting membranes and solid electrolyte materials based on block copolymers.