Applications and Prospects of Polymers in Soft-Matter Electronic Devices

Introduction

Soft-matter electronic devices are a class of electronic devices based on flexible, stretchable, and low-modulus materials. In recent years, they have attracted considerable attention due to their potential in wearable devices, biomedical sensors, and flexible displays.

In these devices, polymers, as macromolecular structures, offer extensive application potential in soft-matter electronics through the diversity of their chain structures and condensed-phase characteristics. The repeating units and degree of polymerization along the polymer chain determine their physical and chemical properties, which in turn directly affect their performance in electronic devices. This article explores the current applications of polymers in functional materials and devices from the perspectives of polymer chain structure and condensed-phase characteristics, together with control strategies, and looks ahead to future directions.

Control Strategies

Polymer Chain Structure

The macromolecular chain structure of a polymer directly determines its physical, chemical, and electronic properties. In soft-matter electronic devices, the following structural features are particularly critical:

• Conjugated polymer chains: Polymeric materials with π–π conjugated structures (such as polythiophenes and polyfluorenes) exhibit excellent electrical conductivity and photoelectric characteristics, and are widely used in organic optoelectronic devices such as organic solar cells and organic light-emitting diodes (OLEDs). Through chemical modification of the conjugated backbone and side chains, the energy gap, charge-carrier mobility, and solubility of the materials can be tuned.

• Block copolymers: By combining monomers with different functions into blocks, polymers with multiple functionalities can be designed. For example, polystyrene–polydimethylsiloxane block copolymers demonstrate excellent mechanical and dielectric properties in the field of flexible electronics.

• Cross-linked network structures: Polymers that form three-dimensional network structures through cross-linking possess higher mechanical stability, making them suitable for electronic devices in high-strain environments.

Condensed-Phase Characteristics

The condensed-phase characteristics of polymer materials significantly affect their performance in devices. Through microphase separation and by controlling molecular weight, block composition, and processing conditions, nanoscale microphase-separated structures can be achieved, improving charge-transport efficiency and mechanical properties. In semiconducting polymers, appropriate crystallinity can be controlled to tune electronic transport performance; excessive crystallinity, however, may increase brittleness. During polymer-chain construction, methods such as stretching, coating, or electric-field-assisted alignment can be employed to achieve precise synthesis of polymer chains through precise electric-field regulation. In addition, electrodeposited conducting polymers can effectively suppress volume expansion of metal compounds and provide fast electron-transfer pathways for electrodes, thereby improving the cycling stability of electrode materials.

Practical Applications

Flexible Materials

In light-emitting devices, polymer light-emitting materials have become an important component of flexible displays thanks to their high electroluminescence efficiency and flexible processability—for example, organic electronic diodes with higher charge-carrier mobility facilitate charge injection and transport in devices. In display devices, polymer electrochromic materials can be used in flexible e-paper and smart windows. Moreover, to bond multiple functional layers in flexible screens, flexible adhesives also employ polymers to improve optical performance.

In flexible sensors, conducting polymers are widely used in strain, pressure, and temperature sensors because of their high sensitivity and mechanical flexibility—for example, PEDOT:PSS exhibits high fatigue resistance, flexibility, and stretchability. Ion-conducting polymers are used in wearable biomedical sensors to enable real-time monitoring of human physiological signals. Metal–organic frameworks (MOFs) are porous materials with periodic network structures self-assembled from metal ions and bridging organic ligands, featuring large surface areas and good thermal stability. Because noble-metal nanomaterials tend to aggregate, MOFs can serve as frameworks to protect enzymes and enhance their catalytic activity.

Energy Storage Materials

Polymer electrolytes provide excellent ionic conductivity and safety in flexible lithium-ion batteries, improving the cycling stability and electrochemical performance of electrode materials—for example, in supercapacitors. Lignin-based conductive hydrogels, cross-linked from lignin and its derivatives, maintain good electrochemical performance even at low temperatures, making them excellent matrices for supercapacitors.

Polymers can produce considerable deformation while maintaining stable properties. Furthermore, high-molecular-weight polymer films also exhibit a wide temperature span, making them promising as next-generation refrigerant materials.

Polymer solar cells show tremendous potential because of their light weight, flexibility, and large-area manufacturability. n-type polymer electron acceptors, with advantages such as tunable energy levels, high absorption coefficients, and excellent electrical and photoelectric properties, have significantly improved the power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs).

Medical Materials

Biocompatible polymers are used in flexible electronic skin and implantable medical devices. Microporous polyurethane piezoelectric materials have been synthesized by mixing ferroelectric ceramic particles into a rubber polymer matrix; simultaneously, gas is introduced into the system through a foaming process to form uniformly distributed spherical inclusions, effectively reducing the dielectric constant of the polymer and significantly improving piezoelectric voltage sensitivity.

Polymers with stimulus-responsive characteristics show unique advantages in drug release and biosensing. Nucleic-acid hydrogels possess good hydrophilicity, tunability, and biocompatibility, together with stimulus responsiveness, high sensitivity, and strong effectiveness, and allow visual judgment by the naked eye, overcoming to some extent the limitations of expensive analytical equipment and complex operation.

Future Outlook

In the transition from traditional fossil fuels to renewable energy, eco-friendly materials offer excellent sustainability and biodegradability. Applying sustainable materials in electronic devices can yield industrial benefits from waste biomass resources and play a role in environmental protection.

The integration of artificial intelligence with soft matter to predict structures has excellent prospects. By applying machine learning to the prediction of various properties and characteristics of polymers, resource and time costs can be effectively reduced, the R&D efficiency of new materials can be improved, and scientific guidance and theoretical support can be provided for related experiments.

Polymers are highly compatible with biomedicine. Medical polymer materials have broad application fields, covering everything from drug delivery to tissue engineering. In drug delivery, polymer materials are used to construct controlled-release systems to optimize therapeutic efficacy and reduce side effects. In tissue engineering, these materials serve as scaffolds to mimic the natural extracellular matrix, promoting cell adhesion, proliferation, and new tissue formation.

In summary, polymer materials demonstrate tremendous application potential and broad prospects in the field of soft-matter electronic devices. Through in-depth study of their molecular structures and condensed-phase characteristics, and by developing new control and processing strategies, future flexible electronic devices are expected to achieve more intelligent, multifunctional, and sustainable innovative breakthroughs, further expanding their application horizons.

References

1. M. J. Han and D. K. Yoon. Research Progress in Soft-Matter Materials for Sustainable Electronic Devices. Engineering, 7(5):50–84, 2021.

2. Wu, Liu, Shi, Wang, and Zhang. Preparation and Properties of PEDOT:PSS Flexible Electrodes and Their Light-Emitting Electrochemical Cells. Fine Chemicals, pages 1–13.

3. Wu, Gao, and Liu. Research and Application Progress of High-Sensitivity Flexible Electronic Skin. Transducer and Microsystem Technologies, 42(7):1–5+22, 2023.

4. Sun, Zhou, and Meng. Application of Electrodeposited Conducting Polymers in Flexible Supercapacitors. New Chemical Materials, 52(S2):356–359+364, 2024.

5. Zhang, Yu, Chen, Liu, Li, and Zhou. Lignin-Based Conductive Hydrogels and Their Application in Supercapacitor Electrolytes. Transactions of China Pulp and Paper, pages 1–9.

6. Fang. Preparation and Properties of Flexible Display Optical Transparent Pressure-Sensitive Adhesives Based on Different Chemical Cross-Linking Methods. Ph.D., South China University of Technology, 2023.

7. Du. Application of High-Molecular-Weight Polymers in Intelligent Medical Engineering—Frontier Exploration of Medical Polymer Materials. Modern Salt and Chemical Industry, 51(5):1–3, 2024.

8. Lin, Zhang, Guo, Wu, Cao, Chen, Shuai, and Wu. Structure, Properties, and Applications of Typical Soft-Matter Systems. Journal of Xiamen University (Natural Science), 60(3):520–533, 2021.

9. Duan, Lin, Ding, Wang, and Wang. Research Progress on Materials for Flexible Strain Sensors and Their Applications. New Chemical Materials, 52(S2):42–48, 2024.

10. Wang, Guo, Guo, Huang, Yi, and Zhang. Stimulus-Responsive Multifunctional Nucleic-Acid Hydrogels Based on Cell Capture and Release. Progress in Chemistry, 36(10):1567–1580, 2024.

11. Xiao. Preliminary Study of Functional Polymers and Their Application in Electronic Materials. Wireless Internet Technology, 15(2):108–109, 2018.

12. Hu. Application of Machine Learning and Its Mathematical Theory in Predicting Polymer Material Properties. M.S., Beijing University of Chemical Technology, 2024.

13. Zhao. Simulation Study of Belt-Scalable Electrothermal Refrigeration Structures. M.S., Zhengzhou University, 2024.

14. Du Zhanhong and Y. L. Zhanhong Du. Research Progress in Implantable Neural Electrode Array Devices and Materials. Acta Physico-Chimica Sinica, 36(12):2007004, Aug. 2020.