All Publications

  • Tuning the Mobility of Indacenodithiophene-Based Conjugated Polymers via Coplanar Backbone Engineering CHEMISTRY OF MATERIALS Ji, X., Cheng, H., Schuster, N. J., LeCroy, G. S., Zhang, S., Wu, Y., Michalek, L., Nguyen, B. T., Chiong, J. A., Schrock, M., Tomo, Y., Rech, J., Salleo, A., Gam, S., Lee, G., Tok, J., Bao, Z. 2023; 36 (1): 256-265
  • Degradable semiconducting polymers without long-range order for on-demand degradation of transient electronics JOURNAL OF MATERIALS CHEMISTRY C Chiong, J. A., Michalek, L., Pena-Alcantara, A. E., Ji, X., Schuster, N. J., Bao, Z. 2023

    View details for DOI 10.1039/d3tc03079b

    View details for Web of Science ID 001090295600001

  • Environmentally stable and stretchable polymer electronics enabled by surface-tethered nanostructured molecular-level protection. Nature nanotechnology Zheng, Y., Michalek, L., Liu, Q., Wu, Y., Kim, H., Sayavong, P., Yu, W., Zhong, D., Zhao, C., Yu, Z., Chiong, J. A., Gong, H., Ji, X., Liu, D., Zhang, S., Prine, N., Zhang, Z., Wang, W., Tok, J. B., Gu, X., Cui, Y., Kang, J., Bao, Z. 2023


    Stretchable polymer semiconductors (PSCs) are essential for soft stretchable electronics. However, their environmental stability remains a longstanding concern. Here we report a surface-tethered stretchable molecular protecting layer to realize stretchable polymer electronics that are stable in direct contact with physiological fluids, containing water, ions and biofluids. This is achieved through the covalent functionalization of fluoroalkyl chains onto a stretchable PSC film surface to form densely packed nanostructures. The nanostructured fluorinated molecular protection layer (FMPL) improves the PSC operational stability over an extended period of 82 days and maintains its protection under mechanical deformation. We attribute the ability of FMPL to block water absorption and diffusion to its hydrophobicity and high fluorination surface density. The protection effect of the FMPL (~6 nm thickness) outperforms various micrometre-thick stretchable polymer encapsulants, leading to a stable PSC charge carrier mobility of ~1 cm2 V-1 s-1 in harsh environments such as in 85-90%-humidity air for 56 days or in water or artificial sweat for 42 days (as a benchmark, the unprotected PSC mobility degraded to 10-6 cm2 V-1 s-1 in the same period). The FMPL also improved the PSC stability against photo-oxidative degradation in air. Overall, we believe that our surface tethering of the nanostructured FMPL is a promising approach to achieve highly environmentally stable and stretchable polymer electronics.

    View details for DOI 10.1038/s41565-023-01418-y

    View details for PubMedID 37322142

  • Realizing Intrinsically Stretchable Semiconducting Polymer Films by Nontoxic Additives ACS MATERIALS LETTERS Cheng, H., Zhang, S., Michalek, L., Ji, X., Luo, S., Cooper, C. B., Gong, H., Nikzad, S., Chiong, J. A., Wu, Y., Zheng, Y., Liu, Q., Zhong, D., Lei, Y., Tomo, Y., Wei, K., Zhou, D., Tok, J., Bao, Z. 2022; 4 (11): 2328-2336
  • Formation Mechanism of Flower-like Polyacrylonitrile Particles. Journal of the American Chemical Society Gong, H., Ilavsky, J., Kuzmenko, I., Chen, S., Yan, H., Cooper, C. B., Chen, G., Chen, Y., Chiong, J. A., Jiang, Y., Lai, J., Zheng, Y., Stone, K. H., Huelsenbeck, L., Giri, G., Tok, J. B., Bao, Z. 2022


    Flower-like polyacrylonitrile (PAN) particles have shown promising performance for numerous applications, including sensors, catalysis, and energy storage. However, the detailed formation process of these unique structures during polymerization has not been investigated. Here, we elucidate the formation process of flower-like PAN particles through a series of in situ and ex situ experiments. We have the following key findings. First, lamellar petals within the flower-like particles were predominantly orthorhombic PAN crystals. Second, branching of the lamellae during the particle formation arose from PAN's fast nucleation and growth on pre-existing PAN crystals, which was driven by the poor solubility of PAN in the reaction solvent. Third, the particles were formed to maintain a constant center-to-center distance during the reaction. The separation distance was attributed to strong electrostatic repulsion, which resulted in the final particles' spherical shape and uniform size. Lastly, we employed the understanding of the formation mechanism to tune the PAN particles' morphology using several experimental parameters including incorporating comonomers, changing temperature, adding nucleation seeds, and adjusting the monomer concentration. These findings provide important insights into the bottom-up design of advanced nanostructured PAN-based materials and controlled polymer nanostructure self-assemblies.

    View details for DOI 10.1021/jacs.2c07032

    View details for PubMedID 36102706

  • Tuning the Mechanical and Electric Properties of Conjugated Polymer Semiconductors: Side-Chain Design Based on Asymmetric Benzodithiophene Building Blocks ADVANCED FUNCTIONAL MATERIALS Liu, D., Lei, Y., Ji, X., Wu, Y., Lin, Y., Wang, Y., Zhang, S., Zheng, Y., Chen, Y., Lai, J., Zhong, D., Cheng, H., Chiong, J. A., Gu, X., Gam, S., Yun, Y., Tok, J., Bao, Z. 2022
  • Impact of Molecular Design on Degradation Lifetimes of Degradable Imine-Based Semiconducting Polymers. Journal of the American Chemical Society Chiong, J. A., Zheng, Y., Zhang, S., Ma, G., Wu, Y., Ngaruka, G., Lin, Y., Gu, X., Bao, Z. 2022


    Transient electronics are a rapidly emerging field due to their potential applications in the environment and human health. Recently, a few studies have incorporated acid-labile imine bonds into polymer semiconductors to impart transience; however, understanding of the structure-degradation property relationships of these polymers is limited. In this study, we systematically design and characterize a series of fully degradable diketopyrrolopyrrole-based polymers with engineered sidechains to investigate the impact of several molecular design parameters on the degradation lifetimes of these polymers. By monitoring degradation kinetics via ultraviolet-visible spectroscopy, we reveal that polymer degradation in solution is aggregation-dependent based on the branching point and Mn, with accelerated degradation rates facilitated by decreasing aggregation. Additionally, increasing the hydrophilicity of the polymers promotes water diffusion and therefore acid hydrolysis of the imine bonds along the polymer backbone. The aggregation properties and degradation lifetimes of these polymers rely heavily on solvent, with polymers in chlorobenzene taking six times as long to degrade as in chloroform. We develop a new method for quantifying the degradation of polymers in the thin film and observe that similar factors and considerations (e.g., interchain order, crystallite size, and hydrophilicity) used for designing high-performance semiconductors impact the degradation of imine-based polymer semiconductors. We found that terpolymerization serves as an attractive approach for achieving degradable semiconductors with both good charge transport and tuned degradation properties. This study provides crucial principles for the molecular design of degradable semiconducting polymers, and we anticipate that these findings will expedite progress toward transient electronics with controlled lifetimes.

    View details for DOI 10.1021/jacs.1c12845

    View details for PubMedID 35179880

  • Metal-hydrogen-pi-bonded organic frameworks DALTON TRANSACTIONS Zhu, J., Samperisi, L., Kalaj, M., Chiong, J. A., Bailey, J. B., Zhang, Z., Yu, C., Sikma, R., Zou, X., Cohen, S. M., Huang, Z., Tezcan, F. 2022; 51 (5): 1927-1935


    We report the synthesis and characterization of a new series of permanently porous, three-dimensional metal-organic frameworks (MOFs), M-HAF-2 (M = Fe, Ga, or In), constructed from tetratopic, hydroxamate-based, chelating linkers. The structure of M-HAF-2 was determined by three-dimensional electron diffraction (3D ED), revealing a unique interpenetrated hcb-a net topology. This unusual topology is enabled by the presence of free hydroxamic acid groups, which lead to the formation of a diverse network of cooperative interactions comprising metal-hydroxamate coordination interactions at single metal nodes, staggered π-π interactions between linkers, and H-bonding interactions between metal-coordinated and free hydroxamate groups. Such extensive, multimodal interconnectivity is reminiscent of the complex, noncovalent interaction networks of proteins and endows M-HAF-2 frameworks with high thermal and chemical stability and allows them to readily undergo postsynthetic metal ion exchange (PSE) between trivalent metal ions. We demonstrate that M-HAF-2 can serve as versatile porous materials for ionic separations, aided by one-dimensional channels lined by continuously π-stacked aromatic groups and H-bonding hydroxamate functionalities. As an addition to the small group of hydroxamic acid-based MOFs, M-HAF-2 represents a structural merger between MOFs and hydrogen-bonded organic frameworks (HOFs) and illustrates the utility of non-canonical metal-coordinating functionalities in the discovery of new bonding and topological patterns in reticular materials.

    View details for DOI 10.1039/d1dt04278e

    View details for Web of Science ID 000741628700001

    View details for PubMedID 35019931

  • Modular Synthesis of Fully Degradable Imine-Based Semiconducting p-Type and n-Type Polymers CHEMISTRY OF MATERIALS Tran, H., Nikzad, S., Chiong, J. A., Schuster, N. J., Pena-Alcantara, A. E., Feig, V. R., Zheng, Y., Bao, Z. 2021; 33 (18): 7465-7474
  • Integrating Emerging Polymer Chemistries for the Advancement of Recyclable, Biodegradable, and Biocompatible Electronics. Advanced science (Weinheim, Baden-Wurttemberg, Germany) Chiong, J. A., Tran, H., Lin, Y., Zheng, Y., Bao, Z. 2021: e2101233


    Through advances in molecular design, understanding of processing parameters, and development of non-traditional device fabrication techniques, the field of wearable and implantable skin-inspired devices is rapidly growing interest in the consumer market. Like previous technological advances, economic growth and efficiency is anticipated, as these devices will enable an augmented level of interaction between humans and the environment. However, the parallel growing electronic waste that is yet to be addressed has already left an adverse impact on the environment and human health. Looking forward, it is imperative to develop both human- and environmentally-friendly electronics, which are contingent on emerging recyclable, biodegradable, and biocompatible polymer technologies. This review provides definitions for recyclable, biodegradable, and biocompatible polymers based on reported literature, an overview of the analytical techniques used to characterize mechanical and chemical property changes, and standard policies for real-life applications. Then, various strategies in designing the next-generation of polymers to be recyclable, biodegradable, or biocompatible with enhanced functionalities relative to traditional or commercial polymers are discussed. Finally, electronics that exhibit an element of recyclability, biodegradability, or biocompatibility with new molecular design are highlighted with the anticipation of integrating emerging polymer chemistries into future electronic devices.

    View details for DOI 10.1002/advs.202101233

    View details for PubMedID 34014619