Diffusing wave spectroscopy as an innovative tool to study gelation of bulk materials

 
Diffusing Wave Spectroscopy (DWS) is an optical, which is based on the time-resolved analysis of multiple backscattered light. The backscattered light forms so-called interferential images, which evolve in time in the same way as the particles move in the sample due to Brownian motion. Shortly, the faster the particles move, the faster evolve the images. By a mathematical processing of sets of images, the motion of the particles can be assessed. A thorough information of viscoelastic properties about the surrounding media is obtained. The higher viscosity or elasticity, the more slowly move the particles. DWS does not interfere mechanically with the sample, and is therefore perfectly adapted to study sol-gel processes, without disturbing the gel network formation. Moreover, a fully automated algorithm allows the determination of the gel point. This work will introduce the basics of DWS and how it can be used for the elaboration of mesoporous silica materials, ceramic inks for 3D printing and aerogels.