Tuning the rheological properties of sols for low-density aerogel coating applications
Coating of cylindrical and spherical surfaces with thin and homogeneous low-density aerogel films requires precise control over viscosity and gel time. If the viscosity is too low, shear forces can damage the growing gel network and prevent the formation of uniform coatings. Using the example of dicyclopentadiene-based polymer gels, we demonstrate that the gelation behaviour can be manipulated by reducing the amount of cross-linking through co-polymerization with a monomer that can only form linear chains. Even small additions of a linear co-polymer (1–10 wt. %) increase the viscosity at the sol–gel transition by several orders of magnitude, and drastically improve the uniformity of gel films formed under the influence of shear. These results are discussed in the context of the classical gel theory.