Biomimetic Sequence-Templating Approach Towards a Multiscale Modulation of Chromogenic Polymer Material Properties

Polydiacetylene (PDA) is an established conjugated polymer material useful as a colorimetric indicator of environmental conditions, such as small molecule binding, mechanical force, heat, or solvent, for multiple sensing applications due to the structural dependence of their optical and electronic properties. With its emerging utility for biological applications, there is a critical need to develop PDAs that can be processed in the physiological-relevant environment with predictive structures and properties. Using sequence-tunable peptidic supramolecular interactions to template diacetylene monomer assembly offers a facile synthetic approach and enables a way to rationally influence PDA structure and properties via peptide sequence engineering. This presentation focuses on investigating the structural influences of peptide templating groups on PDA structures and functional properties across length scales by molecularly controlling the properties of peptide moieties through steric effects and hydrophobic interactions. In particular, a library of peptide-PDA conjugates with systematically varied dipeptide segments is established to demonstrate the influence of residue sterics, polarity, and position of substitution on multiscale PDA material properties. We show that steric effects predominantly influence the electronic structure and resulting trends in chain conformation-dependent photophysical properties. On the other hand, distinct trends were observed for bulk properties, such as film conductivity and cellular response to material interfacing. By tuning peptidic molecular volume and polarity, we exhibited a general increase in conductivity with smaller peptide molecular volume and higher hydrophobicity. The properties of peptide-PDA films suggest more interplay between residue size and hydrophobicity at larger length scales. In summary, this work provides new molecular-level insights on how sequence-tunable sterics and polarity can be used as a synthetic handle to rationally modulate multiscale structure-function correlations for peptide-PDAs as functional biomaterials. These findings pave the way for further developing sequence-defined programmable properties and complex behavior for peptide-PDAs, such as the adaptive evolution of their properties in response to living systems interfaced with these functional biomaterials in physiologically relevant environments.