Manipulating the ABCs of self-assembly via low-χ block polymer design

Block polymer self-assembly typically translates molecular chain connectivity into mesoscale structure by exploiting incompatible blocks with large interaction parameters (chi(ij)). In this article, we demonstrate that the converse approach, encoding low-chi interactions in ABC bottlebrush triblock terpolymers (chi(AC) less than or similar to 0), promotes organization into a unique mixed-domain lamellar morphology, which we designate LAM(P). Transmission electron microscopy indicates that LAM(P) exhibits ACBC domain connectivity, in contrast to conventional three-domain lamellae (LAM(3)) with ABCB periods. Complementary small-angle X-ray scattering experiments reveal a strongly decreasing domain spacing with increasing total molar mass. Self-consistent field theory reinforces these observations and predicts that LAM(P) is thermodynamically stable below a critical chi(AC), above which LAM(3) emerges. Both experiments and theory expose close analogies to ABA' triblock copolymer phase behavior, collectively suggesting that low-(chi) interactions between chemically similar or distinct blocks intimately influence self-assembly. These conclusions provide fresh opportunities for block polymer design with potential consequences spanning all self-assembling soft materials.