Study of the surfactant role in latex–aerogel systems by scanning transmission electron microscopy on aqueous suspensions

Summary For insulation applications, boards thinner than 2 cm are under design with specific thermal conductivities lower than 15 mW m−1 K−1. This requires binding slightly hydrophobic aerogels which are highly nanoporous granular materials. To reach this step and ensure insulation board durability at the building scale, it is compulsory to design, characterise and analyse the microstructure at the nanoscale. It is indeed necessary to understand how the solid material is formed from a liquid suspension. This issue is addressed in this paper through wet‐STEM experiments carried out in an Environmental Scanning Electron Microscope (ESEM). Latex–surfactant binary blends and latex–surfactant–aerogel ternary systems are studied, with two different surfactants of very different chemical structures. Image analysis is used to distinguish the different components and get quantitative morphological parameters which describe the sample architecture. The evolution of such morphological parameters during water evaporation permits a good understanding of the role of the surfactant. Lay description Global warming and climate change due to the combustion of fossil fuels are global issues. The accepted political solution is to decrease our CO2 emissions. This implies to develop renewable energies but also to reduce the energy demand. As buildings are the world's leading source of energy consumption, many efforts are being focused on thermal insulating when renovating buildings. Several solutions are currently proposed, such as adding a thicker layer of a classical material on the walls, or a multilayer product including insulating materials. Because a large thickness is required to reach a sufficiently high thermal resistance, these systems lead to either complex façades in the case of external insulation, or to a considerable loss of habitable space in the case of internal insulation. To overcome these issues, the main goal is to reduce the intrinsic thermal conductivity of the insulating layer to reach higher thermal resistance with lower thickness. Nanostructured silica is an excellent base product candidate for manufacturing efficient/durable thermal superinsulation products with low production costs. However, in order to design insulation products with nanostructured silica grains inside, one has to ensure simultaneously some thermal properties and other functional properties. The protection against moisture is ensured by a hydrophobic treatment of nanostructured sili