Combinations of fluorinated and silicone based elastomers were elaborated through the in situ synthesis of interpenetrating polymer networks (IPNs). The PDMS network was formed by dibutyltindilaurate catalyzed addition between the hydroxy end groups of alpha,omega-(3-hydroxypropyl)polydimethylsiloxane (PDMS) and a pluriisocyanate cross-linker. The poly(fluorinated acrylate) (polyAcRf6) network was obtained from free-radical copolymerization of a fluorinated acrylate with ethylene glycol dimethacrylate in the presence of dicyclohexyl peroxydicarbonate as the initiator. IPNs with different relative weight proportions of the fluorinated vs silicone partners were characterized by DMTA and DSC. Density refractive index and contact angle measurements reveal a satisfactory interpenetration degree of PDMS and polyAcRf6 networks. In addition, these materials present an unusual variation of density values and of the surface properties as a function of the relative weight composition. (c) 2006 Elsevier Ltd. All rights reserved.