(505h) Using Sequence-Defined, Bioinspired Polymers to Understand Chain Conformation Effects in Block Copolymer Self-Assembly

The fundamental physics governing self-assembly is key to designing nanostructured materials from block copolymers with intricate chemical patterns and chain conformations. Yet the understanding of chain formation effects beyond conventional coil–coil and rod–coil block copolymers remains elusive, partially due to the challenge to precisely tune chain conformation without introducing other complicating factors. Sequence-defined polymers allow precise control over monomer sequence and chain conformation, providing unique opportunities for systemic investigation of polymer chain characteristics in block copolymer self-assembly.

In this talk, I will discuss our work utilizing a class of sequence-defined peptidomimetic polymers, polypeptoids, to investigate the effects of helical chain conformation on the thermodynamics of block copolymer self-assembly. In a model poly(n-butyl acrylate)–polypeptoid block copolymer that self-assembles into lamellae, the polypeptoid block is designed as the conformationally tunable block that adopts either a helical or a coil chain conformation depending on monomer chirality. The helical chain conformation is shown to decrease the order–disorder transition temperature (T_ODT) of the coil–helix block copolymer comparing to its coil–coil analogue, due to a combination of decreased enthalpic interactions (smaller χ) and amplified chain stretching. Furthermore, chain conformation effects near the domain interface are studied with a model polystyrene–polypeptoid block copolymer, where the conformation of a short peptoid segment near the block junction is tuned to be helical or coil. The chain conformation of a short segment at the vicinity of the interface is shown to be critical to drive the self-assembly morphology, and impact the formation and stability of the double gyroid network phase.

The findings highlight the importance of chain conformation on the self-assembly thermodynamics in block copolymers with nonideal chain conformations, and polypeptoids as highly-controlled, precise polymers to aid the fundamental understanding of effects from polymer chain characteristics to establish structure–property relationships for efficient design of soft materials.