Conductive polymers have great application potential in frontier fields such as semiconductors and new energy due to the flexibility of polymers and the optoelectronic properties of metals or semiconductors, as well as the advantages of light weight, low cost and easy processing. However, the practical application of conductive polymers is seriously hindered by the distortion and entanglement of entropy-driven molecular chains during synthesis that can lead to poor material and device consistency. Although nano-spatially confined nanospace, interface-induced assembly, and epitaxial growth have been developed to synthesize two-dimensional conductive polymers to address these challenges, there is still a lack of large-scale synthesis methods for ordered conductive polymers.
In order to solve this problem, the Xue Mianqi team of the Institute of Physics and Chemistry of the Chinese Academy of Sciences has creatively developed an interfacial confined polymerization method for a kind of biomineralization, which can realize the preparation of large-area two-dimensional conductive polymer films on any substrate, which can easily adjust the thickness and transparency while having a high degree of order, and shows great application potential in the field of smart buildings and energy management. At the same time, the design mechanism of this method is applicable to other lightweight organic materials with similar synthesis paths, which provides a simple and effective large-scale fabrication method for the development of next-generation high-performance organic semiconductor devices, wearable devices, new optoelectronic devices, and intelligent sensing devices. The study was titled "A Universal Biomineralization-Like Interfacial-Confined Strategy Enables Practicable, Meter-Scale, Transmittance-Adjustable, Highly-Ordered, Photothermal-Capable, 2D." Conducting Polymers" was published in the latest issue of Advanced Functional Materials.
Based on the inspiration of the biomineralization process, the authors proposed a simple and universal method to construct highly stable and practical ordered two-dimensional conductive polymer films on different substrate surfaces. Taking the preparation of large-size ordered polypyrrole film on polyethylene terephthalate (PET) substrate as an example, a liquid-phase system with the coexistence of monomer pyrrole and oxidant was selected, and the PET substrate was placed on its surface to form an interface confinement environment with good contact. The oligomers formed in the liquid phase spontaneously complete the flotation process due to their own properties (hydrogen bonding makes the pyrrole monomer and water relatively stable, and when the oligomers such as dimers appear, the hydrogen bonding is partially destroyed, the oligomers or aggregates with larger molecular weight will sink due to gravity, and the dimers with smaller molecular weights will float to the solid-liquid interface), and are arranged regularly at the interface under the synergistic induction of water and substrate, and then polymerized into an orderly two-dimensional polypyrrole film. In this method, there is no need to construct a separate confined space or two-dimensional template, and the oligomers are only anchored at the interface in an orderly manner by relying on the interaction with water and substrate, simplifying the preparation process and directly using the target substrate for in-situ reactions.
Fig.1 Schematic diagram of the synthesis of polypyrrole by the confined polymerization method at the interface of quasi-mineralization. It should be noted that this method is highly universal, and conductive polymers can achieve two-dimensional growth of any size on any substrate. Taking polypyrrole as an example, the method achieves large-scale growth on polyethylene terephthalate, polymethyl methacrylate, graphite paper, glass, silica, polydimethylsiloxane, polypropylene, aluminum foil, copper foil, stainless steel foil and other material substrates. In addition, the size of the 2D polymer film obtained by this reaction is currently limited only by the size of the reaction vessel, which means that the size of the conductive polymer can be easily met for most practical applications (Figure 2).
Fig.2 Actual diagram of polypyrrole prepared on different substrates. 【Morphological characterization of ordered polypyrrole films】Figure 3a shows the ordered polypyrrole films synthesized with PET as substrates, with a size of up to 30 cm*65 cm (which is consistent with the size of the reaction vessel shown in Figure 2b), from top to bottom, which are single-layer, double-layer, and triple-layer polypyrrole films. It can be seen that the multilayer assembly of conductive polymers can be easily realized by this method, so as to realize the regulation of their thickness, light transmittance and conductivity, and provide further support for the practical application of conductive polymers. Figures 3b and c are scanning electron microscope images of an ordered polypyrrole film, where the folds are derived from the flexibility of the membrane during transfer. Atomic force microscopy images show that the thickness of the film is about 20-30 nanometers, and some areas are stacked due to the formation of folds, reaching a thickness of about 90 nanometers.
Fig.3 Optical image and morphological structure characterization of polypyrrole films. 【Characterization of the ordered structure of polypyrrole films】Figure 4 is the characterization of the structure and properties of polypyrrole films. In the high-resolution transmission electron microscopy images, some areas showed obvious lattice fringes (d=0.37 nm), indicating that the synthesized polypyrrole film was partially crystalline. After the Fast Fourier Transform (FFT), a distinct Bragg diffraction spot can be seen. The X-ray diffraction pattern shows four sharp diffraction peaks at 2θ = 9.2, 12.0, 23.8, and 35.9°, indicating that the synthesized polypyrrole sample has a high degree of order. According to the Bragg equation, the corresponding spacing is about 9.6, 7.4, 3.7 and 2.5 Å, indicating that the layer spacing of the synthesized polypyrrole film is about 3.7 Å, which is consistent with the FFT image. Raman tests and Fourier transform infrared spectroscopy further verified the order of the prepared films.
Fig.4 Order-based characterization of polypyrrole films. Summary: The authors have developed an interfacial confinement strategy for a kind of biomineralization to realize the construction of large-scale ordered two-dimensional conductive polymer systems, which provides the possibility for the practical application of conductive polymers in green buildings, energy management and other fields. At the same time, this general strategy can be applied to the large-scale orderly preparation of other light organic materials with similar synthetic routes, which provides a positive reference for solving the long-term stability and large-scale application of light organic or organic-inorganic composites based on conductive polymers. Original link:
https://doi.org/10.1002/adfm.202316255 Source: Frontiers of Polymer Science