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April 1, 2025 This article has been reviewed according to Science X's editorial process and policies . Editors have highlightedthe following attributes while ensuring the content's credibility: fact-checked peer-reviewed publication trusted source proofread by Waseda University Polysiloxane materials, such as polydimethylsiloxane (PDMS)-based elastomers, exhibit a self-healing capability by the introduction of silanolate (Si–O – ) groups. This ability stems from their dynamic siloxane (Si–O–Si) bonds, which can break and reform to repair damage.
Their self-healing properties could make them valuable in applications like protective coatings for use in various fields, such as optics, electronics, and aerospace. To improve the properties of PDMS-based materials, they have been combined with inorganic fillers such as nanoparticles or nanosheets. Generally, the introduction of nanosheets into polymers leads to the formation of a layered structure that exhibits superior thermal, mechanical, and gas barrier properties.
Furthermore, an improved crack-healing ability of oriented films has been reported. This improvement is attributed to polymer diffusion concentrated in the in-plane direction. Researchers at Waseda University, Japan, have made significant progress in enhancing self-healing siloxane materials by developing a more efficient method for fabricating multilayered films .
In a study published 6 January 2025, in the journal Chemical Communications , a team led by Professor Atsushi Shimojima, with Research Associate Yoshiaki Miyamoto and Assistant Professor Takamichi Matsuno, fabricated a composite film comprising highly cross-linked organosiloxane (silsesquioxane) and grafted PDMS layers using a self-assembly process. "Replacing traditional materials with our self-healing material, which is less susceptible to deterioration and has high hardness, would be in high demand for maintenance-free and durable applications," says Miyamoto, the lead author of the study. The researchers began by depositing a solution containing 1,2-bis(triethoxysilyl)ethane, Pluronic P123 (a PEO–PPO–PEO triblock copolymer, where PEO stands for poly( ethylene oxide ) and PPO stands for poly(propylene oxide)), and a PEO–PDMS–PEO block copolymer onto a silicon or glass substrate using spin-coating or drop-casting techniques.
This process formed a thin film with a lamellar (layered) structure. The film was then calcinated in air at 170 °C for 4 hours, resulting in the removal of the PEO and PPO blocks. This process left behind a multilayered structure composed of silsesquioxane and PDMS layers.
To impart self-healing properties to the film, Si–O – groups were introduced. These groups promote rearrangement and reconnection of the siloxane (Si–O–Si) networks. To achieve this, the film was immersed in a solution of tetrahydrofuran, water, and potassium hydroxide (KOH).
In this process, hydroxide ions (OH – ) from KOH removed protons (H + ) from silanol (Si–OH) groups, converting them into Si–O – ions. The final film could repair micrometer-scale cracks when heated to 80 °C at 40% relative humidity for 24 hours. The film showed superior properties compared to conventional PDMS-based materials.
The cross-linked organosiloxane layers provided greater rigidity and served as a barrier against the volatilization of cyclic siloxanes, addressing the limitations of traditional PDMS materials. While conventional self-healing PDMS elastomers have a hardness of 49 MPa, the final self-healing film exhibited a hardness of 1.50 GPa.
"This innovative multilayered design allows our material to be both harder and more heat-resistant than existing self-healing siloxane-based materials, paving the way for more durable and reliable applications," says Miyamoto. With its high hardness and self-healing properties, this material is well-suited for protective coatings, flexible electronics, and other applications that require long-lasting performance. More information: Yoshiaki Miyamoto et al, Multilayered organosiloxane films with self-healing ability converted from block copolymer nanocomposites, Chemical Communications (2025).
DOI: 10.1039/D4CC05804F Journal information: Chemical Communications Provided by Waseda University.
