Controlling Ensemble Chain Conformations with Precise Sequence Patterning of Polypeptoids

Polymer properties are intimately related to chain structure at the molecular length scale. In biological polymers, control over folded chain shape via primary sequence patterning creates highly selective catalytic sites and nanomachines. Replicating this control over structure and properties through precise tuning of chain sequence affords opportunities to expand applications of polymeric systems. As a first step toward precisely tuned chain shapes, this work uses hydrophobic sequence patterning to narrow and shift the ensemble of chain conformations away from the Gaussian chain statistics of a random coil. Double electron-electron resonance (DEER) spectroscopy reveals that placement of hydrophobes at the chain ends drives the ends together. Meanwhile, scattering results show that this contraction in R_ee is not paired with a concomitant collapse in the overall chain dimensions, demonstrating a decoupling from the classical proportionality of R_g and R_ee with the introduction of sequence.