Metal-Free Photo-Curing of Polysiloxanes using Multifunctional Silirenes as Crosslinkers

Engineers constantly seeks innovative methods to enhance material properties, reduce costs, and improve sustainability. Polysiloxanes, commonly known as silicones, are a class of inorganic polymers with exceptional physical and mechanical properties, making them vital in a wide range of applications across various industries. The cured elastomers of silicones, in particular, have captured a significant share of the silicone market due to their versatile applications. Polysiloxanes come in various forms, including fluids, gels, rubbers, and resins, and they can be tailored to meet specific application requirements. They find use in a wide range of industries, including automotive, aerospace, construction, electronics, cosmetics, and healthcare, among others. The versatility of silicones stems from their unique combination of properties, making them valuable in both industrial and consumer products. However, conventional curing methods involve the use of metal catalysts, such as platinum or tin, which pose environmental and economic challenges. In this context, In a new study published in the peer-reviewed Journal ChemSesChem by Technical University of Munich scientists: Matthias Nobis, Jonas Futter, Dr. Maximilian Moxter, Prof. Dr. Shigeyoshi Inoue, Prof. Dr. Bernhard Rieger developed an innovative, metal-free photo-curing method for silicones using multifunctional silirenes as crosslinker scaffolds.

The authors addressed the need for alternative curing methods that are both efficient and environmentally friendly. They proposed a curing strategy based on silacyclopropenes (silirenes) as crosslinkers, demonstrating the potential of these structures to enable UV-light controlled curing at room temperature across various commonly used PDMS functionalities. The key concept involves utilizing silirenes, three-membered ring systems that can be opened under UV-light to generate transient silylenes. These highly reactive silicon species readily react with common silicone functionalities, such as Si−H, Si−OH, or Si−vinyl, enabling crosslinking of the silicone chains and the creation of elastomers. The study carefully analyzes the photoreactivity of different silirenes towards various silicone functionalities, seeking optimal conditions for efficient curing.

The authors presented a thorough investigation of the reactivity of silirenes with Si−H, Si−OH, and Si−vinyl groups, determining the appropriate silirene structures and reaction conditions for efficient curing. The study highlights the importance of silirene structure and activation wavelength in achieving the desired curing outcomes. Silirenes with specific substituents demonstrated enhanced reactivity, paving the way for the design of efficient crosslinking agents.

Furthermore, the research team discussed the synthesis and characterization of multifunctional silirenes that act as crosslinkers. The researchers developed a method to synthesize higher functional silirenes using a modular approach, achieving higher reactivity and enabling effective crosslinking. The multifunctional silirenes were successfully employed to cure different PDMS functionalities (Si−H, Si−OH, and Si−vinyl), demonstrating the versatility and potential for industrial applications.

The innovative metal-free photo-curing method utilizing multifunctional silirenes as crosslinkers presents a significant advancement in the field of materials engineering. The study successfully demonstrates the feasibility of curing silicones at room temperature using UV light, without the need for metal catalysts. The findings provide valuable insights into the reactivity of silirenes with various silicone functionalities and pave the way for developing efficient and environmentally friendly curing strategies. The new study has promising implications for the silicone industry, offering a more sustainable and cost-effective alternative to conventional curing methods. Further research and optimization of the proposed curing approach could potentially revolutionize the production of silicone elastomers, benefiting a wide range of industries.