Microphase Separation of Hydrogen-Bonded Polystyrene-Polydimethylsiloxane Copolymer Blends

Self-assembled morphologies play a pivotal role in developing material’s properties. It would drive innovation if the transition of self-assembled structures is controlled by external stimulus. Hydrogen bonding (H-bonding) as secondary interaction has combined with a polymer blend system. It can be dissociated and re-associated as a function of temperature, developing reversible bonds. In our system, phenol (Ph) and pyridine (Py) are attached in pendent to polystyrene (PS) and polydimethylsiloxane (PDMS), respectively. The tendency for PS-PDMS to phase-separate competes with the H-bonding attraction of Ph-Py. We observed that macrophase- or microphase separation is dictated by the degree to which H-bonding attraction enhances the inherent immiscibility of PS-PDMS. The broad peaks of small-angle X-ray scattering indicate the formation of disordered nanostructures. An increase in domain size (~20 nm to ~60 nm) with increasing temperature (120-160 degree Celcius) was observed due to progressive dissociation of H-bonds, and this is (partially) reversible. The selective PDMS etching test proves the percolation of PDMS, indicating the original co-continuous nanostructures. This opens new possibilities for fine-tuning the domain size of co-continuous polymer nanostructures.