Geometric divergence in nanostructural fates of coassembled peptides leads to broadening of morphology-based optoelectronic property outcomes

Abstract

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  Morphological fates could be driven by torsional mismatch between supramolecular units
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  Coassembly shows non-additive nanostructure and local chirality
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  Divergence in assembly interactions yields variations in optoelectronic functions

The molecular design of organic electronic materials dictates their hierarchical assembly structure and functional properties, often governing their emergent behavior, especially when they are interfaced with living systems. When π-conjugated units are incorporated into biomolecular networks such as peptide structures, geometric constraints and supramolecular interactions introduce additional complexity to conventional biomolecular assemblies and make structure-property relationships more difficult to predict. Here, we show that torsional mismatch between peptide-functionalized donor and acceptor π-conjugated units can serve as a simple yet powerful design parameter to expand the range of accessible nanostructures and functional properties for a water-processable supramolecular bioelectronic system. Utilizing a sequence-matched peptide system bearing a flexible donor and a rigid acceptor, we demonstrated that each component assembles into distinct structures individually, whereas combining them produces hybrid morphologies, distinct from nanostructures achieved by mixing the separately assembled donor and acceptor units. The resulting coassembled structures exhibit altered chirality and dimensionality, which are more than the sum of their individual components and have an influence on energy-transfer behavior and photocurrent generation of the bulk material. We further demonstrate that assembly pathways, such as thermal annealing and acidification kinetics, can direct the system into different local minima, which enables dynamic control over morphology and function without changing molecular composition. Together, these findings highlight an approach that leverages geometric mismatch and pathway dependence to access diverse assembly structures and functional states for a bioelectronic system, thus establishing a generalizable strategy for designing adaptive, water-processable biomacromolecules with molecularly tunable optoelectronic properties.

Sequence-defined hierarchical structure critically governs the function and emergent properties of biomacromolecules. However, introducing functional yet bulky π-conjugated synthetic units imposes geometric constraints that complicate the rational prediction of structure-morphology correlations for engineered biomacromolecules. Here, we report an intriguing coassembly behavior of a sequence-matched peptide pair bearing energy-transporting π-electron donor/acceptor cores (triaspartic acid [DDD]-quaterthiophene [4T]/DDD-perylene diimide [PDI]). Individually, DDD-4T forms twisted 1D chiral nanofibers, whereas DDD-PDI assembles into achiral 2D bundle-like nanostructures. Upon coassembly, heterotypic interactions between a more torsionally compliant donor core and comparatively rigid acceptor core produce hybrid chiral nanostructures distinct from either pristine state. These variations in nanostructure dimensionality and local chirality result in differential photophysical and optoelectronic properties. Thermal annealing and kinetic control of acidification further direct assemblies into alternative local minima, thereby underscoring pathway-dependent supramolecular interactions. Collectively, we present a design principle for bioelectronic materials whereby broadening of property-defining morphological fates could be driven by torsional mismatch -between supramolecular units.

Sequence-defined hierarchical structure critically governs the function and emergent properties of biomacromolecules. However, introducing functional yet bulky π-conjugated synthetic units imposes geometric constraints that complicate the rational prediction of structure-morphology correlations for engineered biomacromolecules. Here, we report an intriguing coassembly behavior of a sequence-matched peptide pair bearing energy-transporting π-electron donor/acceptor cores (triaspartic acid [DDD]-quaterthiophene [4T]/DDD-perylene diimide [PDI]). Individually, DDD-4T forms twisted 1D chiral nanofibers, whereas DDD-PDI assembles into achiral 2D bundle-like nanostructures. Upon coassembly, heterotypic interactions between a more torsionally compliant donor core and comparatively rigid acceptor core produce hybrid chiral nanostructures distinct from either pristine state. These variations in nanostructure dimensionality and local chirality result in differential photophysical and optoelectronic properties. Thermal annealing and kinetic control of acidification further direct assemblies into alternative local minima, thereby underscoring pathway-dependent supramolecular interactions. Collectively, we present a design principle for bioelectronic materials whereby broadening of property-defining morphological fates could be driven by torsional mismatch -between supramolecular units.

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