Experimental realization of optically transparent, mechanically robust and flexible aerogels has been a longstanding challenge, which limits their practical applications in energy-saving devices, such as thermally insulating films for enhancing energy efficiency of windows. The poor transparency precluded even hypothetical consideration of the possibility of birefringent aerogels. We develop birefringent and optically isotropic aerogels that combine properties of thermal super-insulation, mechanical robustness and flexibility, and transparency to visible-spectrum light. This unusual combination of physical properties is achieved by combining liquid crystalline self-organization of cellulose nanofibers with polysiloxane cross-linking and control of the nanoscale porosity to form hybrid organic-inorganic mesostructured aerogels. Potential applications of these inexpensive materials range from single pane window retrofitting to smart fabrics.

光学透明，机械坚固和柔性气凝胶的实验实现一直是一项长期的挑战，这限制了它们在节能设备（例如用于提高窗户能量效率的隔热膜）中的实际应用。较差的透明度甚至排除了双折射气凝胶可能性的假设性考虑。我们开发了双折射和光学各向同性的气凝胶，这些气凝胶结合了超级隔热，机械强度和柔韧性以及对可见光的透明性。这种不寻常的物理性能组合是通过将纤维素纳米纤维的液晶自组织与聚硅氧烷交联和控制纳米级孔隙率相结合而形成的，从而形成混合的有机-无机介孔结构气凝胶。