Effect of silicone surfactant on the CO₂ bubble nucleation in polyol

Polyol based foams are widely sought-after materials for manufacturing thermal insulators, high resilience foam seating, adhesives, hard plastics for electronic instruments, etc. The polyol foams are produced by the reaction of di-isocyanate with polyol to form polyurethane and water. Some amount of isocyanate reacts with water to produce CO₂. The generated CO₂ nucleates into bubbles within the polymer matrix, forming a foam. Silicone surfactants, made of poly dimethyl-siloxane backbone and polyether branches, are commonly used to stabilize the foam formulation. The silicone surfactants reduce interfacial tension between polyol-CO₂ interface_, promotes bubble generation and impacts the foam cell size. It is also known that the composition of silicone surfactant significantly influences its role in stabilizing the foam formulation as well. However, the physical mechanism of how these silicone surfactants affect the nucleation and stability of the bubbles is not well understood. In this talk, using classical density functional theory models, we propose design principles for silicone surfactants and elucidate the mechanism through which they lead to foams with improved physical properties.