Self-Healing Lamellar Silsesquioxane Thin Films

Abstract

Silsesquioxanes are widely used inorganic−organic hybrid materials because of their high thermal and chemical stability and diverse organic functions. Self-healing of cracks formed in polymeric siloxane networks of silsesquioxanes is crucial for many applications. In this study, we report the design of selfhealing silsesquioxane [(O 3/2 Si−R−SiO 3/2 ) n ] thin films by the selfassembly process. Lamellar-structured thin films were prepared by hydrolysis and polycondensation of bis-alkoxysilane precursors [(EtO) 3 Si−R−Si(OEt) 3 , where R = C 2 H 4 , C 2 H 2 , or C 6 H 4 ] in the presence of a surfactant, followed by spin-coating on substrates. These films exhibit spontaneous and rapid healing of micrometerscale cracks even under mild conditions (at room temperature and 50−60% relative humidity). Compared with the conventional silica-based lamellar thin films prepared using tetraethoxysilane and the surfactant, a significant enhancement of the crack-healing ability is evident. This can be attributed to the higher flexibility of the silsesquioxane networks and the higher swelling ratio of the lamellar silsesquioxane with moisture. Furthermore, the film hardness and adhesion to the substrate were greatly improved by adding a bis-alkoxysilane precursor with a long bridging organic group for interlamellar cross-linking. These results will lead to the development of self-healing silsesquioxane materials for practical applications.

Free‐Blockage Mesoporous Silica Nanoparticles Loaded with Cerium Oxide as ROS‐Responsive and ROS‐Scavenging Nanomedicine

“…b) Schematic representation of Q n structures for the siloxane units of the lattice and T n structures of the organosilane fragments ( n represents the number of associated oxygen bridges with silicon). [ 36a,37 ]…”

“…[ 29 ] Thus, both etching (as suggested by SEM) and partial depolymerization took place within the post‐methylation process of the thiol‐functionalized MSNs, leading to the size reduction and silanol groups accumulation of the target organosilica nanoparticles. It should be kept in mind that the alkaline conditions used in Routes #1 and #2 might affect not only the formation of SiOH groups or the depolymerization process [ 36 ] but also the reformation and/or rearrangement of the siloxane networks in general. [ 36,37 ]…”

“…It should be kept in mind that the alkaline conditions used in Routes #1 and #2 might affect not only the formation of SiOH groups or the depolymerization process [ 36 ] but also the reformation and/or rearrangement of the siloxane networks in general. [ 36,37 ]…”

Polyhedral oligomeric silsesquioxane‐based functional coatings: A review

“…[99] The introduction of self-healing properties into functional coating materials can maintain their integrity and allow them to restore their functionalities, thus extending their lifetime and achieving sustainability. [100,101] To achieve self-healing, noncovalent interaction or dynamic covalent bonds are involved, and the healing process is usually triggered and boosted with an external stimulus such as light, heat, and magnetic field. [101][102][103][104][105][106][107] However, the healing process requires the diffusion of polymer chains in the fractured area, which means that the polymer needs to have a low glass transition temperature and is, therefore, mechanically weak.…”

“…[100,101] To achieve self-healing, noncovalent interaction or dynamic covalent bonds are involved, and the healing process is usually triggered and boosted with an external stimulus such as light, heat, and magnetic field. [101][102][103][104][105][106][107] However, the healing process requires the diffusion of polymer chains in the fractured area, which means that the polymer needs to have a low glass transition temperature and is, therefore, mechanically weak. [108] It is challenging to simultaneously achieve self-healing and strong thermalmechanical properties (e.g., high hardness).…”