(595b) Impact of Helical Chain Shape in Sequence-Defined Polymers on Polypeptoid Block Copolymer Self-Assembly

Davidson, E., Harvard University
Controlling the self-assembly of block copolymers with variable chain shape and stiffness is important for driving the self-assembly of functional materials containing nonideal chains. The polymer helix is a particularly important functional motif in which the scaling relationships between local chain stiffness and space-filling properties impact self-assembly. Polypeptoids, a class of sequence-defined peptidomimetic polymers with controlled helical secondary structure, were used to systematically investigate the impact of helical chain shape on block copolymer self-assembly in a series of poly(n-butyl acrylate)-b-polypeptoid block copolymers. By leveraging sequence control, the precise location of the helix-forming chain section relative to the block junction was controlled. Small-angle X-ray scattering (SAXS) revealed that chain stretching of the helix near the block junction is disfavored, while helical segments at the center of cylindrical domains contribute to unfavorable packing interactions. Finally, temperature-dependent SAXS shows that helix-containing diblock copolymers disorder at lower temperatures than the equivalent unstructured diblock copolymers. These results emphasize that current descriptions of rod/coil interactions and conformational asymmetry for coil polymers do not adequately address the behavior of chain secondary structures in controlling self-assembly.