Tuning Segregation Strength with Sequence-Defined Polypeptoid Diblock Copolymers

Block copolymers with tunable compatibility enable direct control over segregation strength, a key driving force for self-assembly. The miscibility between blocks of an AB copolymer is increased by incorporating B-like units into the A block, and while tapered profiles from semibatch methods have shown compatibilizing effects, fully sequence-defined polymers offer a unique opportunity to control both the composition and distribution of comonomers. We have synthesized polypeptoid–polystyrene diblock copolymers, where the polypeptoid block has styrene-like units precisely incorporated with ether comonomers via high-yielding solid-phase synthesis. First, as styrene-like groups are added to the polypeptoid, the order–disorder transitions (ODTs) are lowered by more than 30 °C. Following this, compatibilizing units are incorporated in different sequences, such as tapered from the block junction or distributed evenly. Within this set of materials with identical composition but different sequence, the ODTs vary by 15 °C. It is expected that sequence affects the effective interaction parameter, chi, which can be quantified using interfacial segregation. These studies demonstrate the ability for sequence control to tune the phase stability of self-assembling block copolymers.