Complex Spherical Phases in a Zwitterion-Tethered Diblock Copolymer Melt

The recent surge of work expanding our understanding of complex spherical packing in block polymers (BPs) has unlocked new design space for the development of advanced soft materials. The continuous matrix phase, which percolates throughout spherical morphologies, is ideal for many applications involving transport of ions or other small molecules. Thus, determining the accessible parameter range of such morphologies is desirable. Bulk zwitterion-containing BPs hold great potential within the realm of electroactive materials while remaining relatively untapped. In this work, three architecturally and compositionally asymmetric diblock polymers were prepared with the majority of blocks having zwitterions tethered to side-chain termini at different ratios. The A15 Frank-Kasper phase was observed in two samples (∼15 kDa), separated by a substantially higher T_ODT after increasing the zwitterion content 1.7-fold. For the highest zwitterion content sample, phase transitioning out of the kinetically trapped, liquid-like packing (LLP) state was found to correlate with a decline in the dielectric strength of zwitterionic relaxation processes, which suggests that zwitterionic interactions are governing the phase transition kinetics. Upon slow cooling from the disordered state, Frank-Kasper phases reappeared with signs of kinetic arrest.