More Like this

1. Computational discovery of high charge mobility self-assembling π-conjugated peptides

   https://doi.org/10.1039/D2ME00017B  

   Shmilovich, Kirill; Yao, Yifan; Tovar, John D.; Katz, Howard E; Schleife, Andre; Ferguson, Andrew L (January 2022, Molecular Systems Design & Engineering)

   Organic electronics offer a route toward electronically active biocompatible soft materials capable of interfacing with biological and living systems. One class of promising organic electronic materials are π-conjugated peptides, synthetic molecules comprising an aromatic core flanked by oligopeptides, that can be engineered to self-assemble into elongated nanostructures with emergent optoelectronic functionality. In this work, we combine molecular dynamics simulations with electronic structure and charge transport calculations to computationally screen for high charge mobility π-conjugated peptides and to elucidate design rules linking aromatic core character with charge mobility. We consider within our screening library variations in the aromatic core chemistry and length of the alkyl chains connecting the oligopeptide wings to the core. After completing our computational screen we identify particular π-conjugated peptides capable of producing self-assembled biocompatible nanoaggregates with predicted hole mobilities of 0.224 cm^2/(Vs) and electron mobilities of 0.143 cm^2/(Vs), and uncover design rules that enhance understanding of the molecular determinants of charge mobility within π-conjugated peptide assemblies. 

   more » « less
2. Hybrid computational–experimental data-driven design of self-assembling π-conjugated peptides

   https://doi.org/10.1039/d1dd00047k  

   Shmilovich, Kirill; Panda, Sayak Subhra; Stouffer, Anna; Tovar, John D.; Ferguson, Andrew L. (January 2022, Digital Discovery)

   Biocompatible molecules with electronic functionality provide a promising substrate for biocompatible electronic devices and electronic interfacing with biological systems. Synthetic oligopeptides composed of an aromatic π-core flanked by oligopeptide wings are a class of molecules that can self-assemble in aqueous environments into supramolecular nanoaggregates with emergent optical and electronic activity. We present an integrated computational–experimental pipeline employing all-atom molecular dynamics simulations and experimental UV-visible spectroscopy within an active learning workflow using deep representational learning and multi-objective and multi-fidelity Bayesian optimization to design π-conjugated peptides programmed to self-assemble into elongated pseudo-1D nanoaggregates with a high degree of H-type co-facial stacking of the π-cores. We consider as our design space the 694 982 unique π-conjugated peptides comprising a quaterthiophene π-core flanked by symmetric oligopeptide wings up to five amino acids in length. After sampling only 1181 molecules (∼0.17% of the design space) by computation and 28 (∼0.004%) by experiment, we identify and experimentally validate a diversity of previously unknown high-performing molecules and extract interpretable design rules linking peptide sequence to emergent supramolecular structure and properties. 

   more » « less
3. Side-chain torsional dynamics strongly influence charge transport in organic semiconductors

   https://doi.org/10.1039/D2CC04979A  

   Banks, Peter A.; Dyer, Adam M.; Whalley, Adam C.; Ruggiero, Michael T. (November 2022, Chemical Communications)

   The role of low-frequency (terahertz) vibrational motions on charge carrier dynamics in organic semiconductors (OSCs) is becoming well-known, and efforts are underway to rationally design new materials to mitigate these detrimental effects. However, most efforts have focused on stabilizing the fused-ring semiconducting ‘core’, often by functionalizing with various side-groups, yet questions regarding the role of such modifications on electron–phonon couplings are still outstanding. In this work, the influence of thiophene rings σ-bonded directly to the π-conjugated cores is explored. The manner in which these groups alter low-frequency vibrational, and resulting electronic, dynamics is quantified using a theoretical approach employing fully-periodic density functional theory (DFT) simulations. Ultimately, these results showcase how the equilibrium geometry and corresponding electronic structure are directly related to detrimental electron–phonon coupling, which have important implications for the design of improved organic optoelectronic materials. 

   more » « less
4. Bridging the crystal and solution structure of a series of lipid-inspired ionic liquids

   https://doi.org/10.1039/D2SM01478E  

   Bellia, Sophia A.; Metzler, Matthew; Huynh, Marissa; Zeller, Matthias; Mirjafari, Arsalan; Cohn, Pamela; Hillesheim, Patrick C. (January 2023, Soft Matter)

   A series of 1,2-dimethylimidazolium ionic liquids bearing a hexadecyl alkyl chain are thoroughly examined via X-ray crystallography. The crystal structures reveal several key variations in the non-covalent interactions in the lipid-like salts. Specifically, distinct cation–cation π interactions are observed when comparing the bromide and iodide structures. Changing the anion to bis(trifluoromethane)sulfonimide (Tf 2 N − ) changes these cation–cation π interactions with anion⋯π interactions. Additionally, several well-defined geometries of the cations are noted based on torsion and core-plane angles of the alkyl chains. Hirshfeld surface analysis is used to distinguish the interactions and geometries in the solid state, helping to reveal characteristic structural fingerprints for the compounds. The solid-state structures of the ionic liquids are correlated with the solution-state structures through UV-vis spectroscopic studies, further emphasizing the importance of the π interactions in the formation of aggregates. Finally, we investigated the thermal properties of the ionic liquids, revealing complex phase transitions for the iodide-containing species. These phase transitions are further rationalized via the analysis of the data gathered from the structures of the other crystallized salts. 

   more » « less
5. The Critical Role of Electron‐Donating Thiophene Groups on the Mechanical and Thermal Properties of Donor–Acceptor Semiconducting Polymers

   https://doi.org/10.1002/aelm.201800899  

   Zhang, Song; Ocheje, Michael_U; Huang, Lifeng; Galuska, Luke; Cao, Zhiqiang; Luo, Shaochuan; Cheng, Yu‐Hsuan; Ehlenberg, Dakota; Goodman, Renée_B; Zhou, Dongshan; et al (March 2019, Advanced Electronic Materials)

   Abstract Organic semiconducting donor–acceptor polymers are promising candidates for stretchable electronics owing to their mechanical compliance. However, the effect of the electron‐donating thiophene group on the thermomechanical properties of conjugated polymers has not been carefully studied. Here, thin‐film mechanical properties are investigated for diketopyrrolopyrrole (DPP)‐based conjugated polymers with varying numbers of isolated thiophene moieties and sizes of fused thiophene rings in the polymer backbone. Interestingly, it is found that these thiophene units act as an antiplasticizer, where more isolated thiophene rings or bigger fused rings result in an increased glass transition temperature (T_g) of the polymer backbone, and consequently elastic modulus of the respective DPP polymers. Detailed morphological studies suggests that all samples show similar semicrystalline morphology. This antiplasticization effect also exists inpara‐azaquinodimethane‐based conjugated polymers, indicating that this can be a general trend for various conjugated polymer systems. Using the knowledge gained above, a new DPP‐based polymer with increased alkyl side chain density through attaching alky chains to the thiophene unit is engineered. The new DPP polymer demonstrates a record lowT_g, and 50% lower elastic modulus than a reference polymer without side‐chain decorated on the thiophene unit. This work provides a general design rule for making low‐T_gconjugated polymers for stretchable electronics. 

   more » « less