Tuning structures and properties of self-healing silsesquioxane films using block copolymers

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Designing self-healing materials is critical for extending product lifespans and reducing waste.
• Siloxane-based materials offer unique properties but often lack inherent repair mechanisms.
• Developing robust, self-healing thin films remains a significant challenge in materials science.

Purpose of the Study:

• To synthesize and characterize organosiloxane-based thin films with intrinsic crack-healing properties.
• To investigate the influence of amphiphilic block copolymers on film morphology and self-healing performance.
• To evaluate the mechanical properties, humidity-induced swelling, and solvent resistance of the developed films.

Main Methods:

• Preparation of organosiloxane thin films using 1,2-bis(triethoxysilyl)ethane and PEO-PPO-PEO block copolymers.
• Evaporation-induced self-assembly to form a lamellar mesostructure.
• Characterization of the mesostructure using techniques to determine periodicity.
• Assessment of crack-healing capability under varying humidity conditions.
• Evaluation of mechanical properties via nanoindentation and solvent resistance through ethanol immersion.

Main Results:

• Formation of a lamellar mesostructure (periodicity 9.56 nm) with alternating polymer and silsesquioxane layers.
• Demonstrated reversible swelling behavior in response to humidity changes.
• Complete crack disappearance observed under 90% relative humidity at room temperature.
• Enhanced nanoindentation hardness and elastic modulus compared to conventional films.
• Maintained mesostructure and crack-healing abilities after ethanol immersion, indicating improved solvent resistance.

Conclusions:

• Polymeric surfactants effectively enhance the mechanical properties and chemical stability of mesostructured siloxane composites.
• The developed organosiloxane films exhibit significant self-healing capabilities, particularly under humid conditions.
• These findings pave the way for self-healing siloxane-based coatings in diverse applications.
• The humidity-responsive swelling is key to the observed crack-healing mechanism.