By Panagiotis N. Manoudis, Dafni Gemenetzis and Ioannis Karapanagiotis
ABSTRACT
Polysiloxane materials have been used in conservation and protection of stone monuments and other
outdoor objects of the cultural heritage for decades. Enhancing the inherent hydrophobic character of the
siloxane materials is highly desirable as it can promote their protection efficacy against the degradation
effects which are induced by rain water and/or humidity. We show that mixing a solution of a polysiloxane
material with a small amount (1% w/w) of silica nanoparticles leads to the formation of a structured surface
which has superhydrophobic properties i.e. the contact angle (CA) of a water droplet on the surface of the
polysiloxane+nanoparticle film is >150°.
We monitor the evaporation process of the water droplet on the surface of the composite
(polysiloxane+nanoparticle) film and show that it follows the same evaporation mode reported for a water
droplet resting on the surface of a natural rose petal. In particular, the evaporation of droplets on both
composite and natural surfaces follows the constant contact radius (CCR) mode: the contact area between
water and surface remains constant with time and the contact angle decreases. Moreover, we report that in
the course of evaporation the relationship of the volume of the droplet to the 2/3 power (V2/3) with time (t)
is linear.
