Molecularly Designed and Nanoconfined Polymer Electronic Materials for Skin-like Electronics

Abstract

Stretchable electronics have seen substantial development in skin-like mechanical properties and functionality thanks to the advancements made in intrinsically stretchable polymer electronic materials. Nanoscale phase separation of polymer materials within an elastic matrix to form one-dimensional nanostructures, namely nanoconfinement, effectively reduces conformational disorders that have long impeded charge transport properties of conjugated polymers. Nanoconfinement results in enhanced charge transport and the addition of skin-like properties. In this Outlook, we highlight the current understanding of structure-property relationships for intrinsically stretchable electronic materials with a focus on the nanoconfinement strategy as a promising approach to incorporate skin-like properties and other functionalities without compromising charge transport. We outline emerging directions and challenges for intrinsically stretchable electronic materials with the aim of constructing skin-like electronic systems.

Figure 1

Key time points along the development path of stretchable electronic materials. Purple text boxes denote significant advances in studies prior to the development of chemically engineered stretchable electronic materials. Yellow text boxes highlight key breakthroughs in intrinsically stretchable electronic materials.

Figure 2

Schematic examples of molecular design strategies to realize both high carrier mobilities and high stretchability. (a) Schematic illustration of the microstructure of conjugated polymer tie chains connecting small aggregates. This type of morphology may be realized with high MW polymers. (b) Schematic of the impact of microstructure on conjugated polymer thin film stretchability. Reproduced from ref (). Available under a CC-BY (Creative Commons Attribution 4.0 International license) license. Copyright 2023 H.-C. Wu et al. (c) Average charge carrier mobilities of polymers from (b) with different MWs under various biaxial strains. Reproduced from ref (). Available under a CC-BY (Creative Commons Attribution 4.0 International license) license. Copyright 2023 H.-C. Wu et al. (d) Photograph of a high MW polymer film under 100% biaxial strain. Reproduced from ref (). Available under a CC-BY (Creative Commons Attribution 4.0 International license) license. Copyright 2023 H.-C. Wu et al. (e) Schematic illustration of adding dynamic interactions. (f) Chemical structures of conjugated polymers with dynamic bonding units. Reprinted with permission from ref (). Copyright 2016 Springer Nature. (g) Charge carrier mobilities of polymers with or without dynamic bonding units under various strains. Reprinted with permission from ref (). Copyright 2016 Springer Nature. (h) Schematic illustration of microstructure of terpolymer. (i) Chemical structures of terpolymers. Reproduced from ref (). Available under a CC-BY (Creative Commons Attribution 4.0 International license) license. Copyright 2021 J. Mun et al. (j) Crack onset strain of the terpolymers. Reproduced from ref (). Available under a CC-BY (Creative Commons Attribution 4.0 International license) license. Copyright 2021 J. Mun et al. (k) Schematic illustration of the microstructure of conjugated polymers with bulky side groups. (l) Chemical structures of conjugated polymers with bulky side chains. Reprinted with permission from ref (). Copyright 2021 American Chemical Society. (m) Optical microscopy images of conjugated polymers with and without bulky side groups under strain. Reprinted with permission from ref (). Copyright 2021 American Chemical Society.

Figure 3

Examples of nanoconfined polymer systems. (a) Schematic illustration of the nanoconfinement strategy. Nanoconfined fibrils are formed directly and are interconnected inside a deformable matrix. Nanoconfinement is important for enhanced charge transport through reducing conformational disorder while an interconnected network is important to both achieve and maintain good charge transport in the strained thin film. (b) Representative functional polymers that produce nanoconfined elastic semiconductors. (c) Representative matrix materials used to induce nanoconfinement in conjugated polymers. The colors of the chemical structures are chosen to match the corresponding conjugated polymers used in nanoconfinement.

Figure 4

Examples of multifunctional stretchable polymer films based on the nanoconfinement strategy. (a) Schematics of the nanoconfinement strategy to realize biodegradability, self-healing ability, photopatterning ability, and surface functionalization/encapsulation in skin-like polymer electronic materials. (b) Chemical structures of the biodegradable elastomer and the degradable semiconducting polymer, and degradability of the nanoconfined film exemplified by the decrease of UV–vis absorption. Reproduced from ref (). Available under a CC-BY license. Copyright 2019 H. Tran et al. (c) Chemical structures of dynamic bonding moieties introduced into the semiconducting polymer and matrix polymer and the self-healing ability of these nanoconfinement systems. Reproduced from ref (). Available under a CC BY-NC (Creative Commons Attribution NonCommercial License 4.0) license. Copyright 2019 American Association for the Advancement of Science. (d) Chemical structures of photo-cross-linkable matrix molecules for PEDOT:PSS and optical microscope image of photo-patterned nanoconfined PEDOT:PSS. Reprinted with permission from ref (). Copyright 2022 American Association for the Advancement of Science. (e) Mechanism of photopatterning ability of semiconducting polymer by selective cross-linking of perfluorophenyl azide end-capped polybutadiene matrix. Reprinted with permission from ref (). Available under a Creative Commons CC BY license. Copyright 2021 Y. Zheng et al. (f) Schematic and long-term sweat stability of environmentally robust nanoconfined semiconducting film achieved by covalently bonded fluorinated molecules onto the nonconjugated C=C bond of the rubber matrix. Reprinted with permission from ref (). Copyright 2023 Springer Nature.