Macromolecules, Vol.32, No.24, 8173-8182, 1999
Networks from alpha,omega-dihydroxypoly(dimethylsiloxane) and (tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane: Surface microstructures and surface characterization
The dibutyltin diacetate-catalyzed reaction of (tridecafluoro-1,1,2, 2-tetrahydrooctyl)triethoxysilane (FTEOS) with dihydroxy-terminated poly(dimethylsiloxane), HO(Me2SiO)(n)H, has been used to prepare surface-modified siloxane networks. Surface characterization of these elastomers was carried out with electron spectroscopy for chemical analysis (ESCA) and optical and atomic force microscopy (AFM). Surface phase separation occurs as a function of FTEOS concentration. For example, FTEOS-6x compositions (where 6x is the initial SiOEt/SiOH ratio) exhibited micron scale "islands" of fluorinated siliceous phase (FSP) surrounded by a siloxane-rich "sea". In FTEOS-12x, the FSP formed a continuous layer on the elastomeric network. Differing dynamic contact angle (DCA) analysis protocols with water as the interrogating fluid showed that water contamination affects force vs distance curve (fdc) data on samples up to FTEOS-10Ox. Intrinsic wetting behavior is reproduced only with a protocol where clean mater is used for each DCA cycle. For FTEOS-12x, an FSP monodomain exists characterized by high theta(adv) (135-6 degrees) and low theta(rec) (55-56 degrees), similar to previously reported values for fluoroalkyl side chain polymers. Long-term testing showed that the coatings undergo slow chemical degradation by water, with the rate depending on composition. FTEOS-12x is chemically stable in water due to the continuous FSP overlayer.
Keywords:INORGANIC HYBRID MATERIALS;DYNAMIC CONTACT ANGLES;BLOCK-COPOLYMERS;SIDE-CHAINS;POLYMERS;POLY(DIMETHYLSILOXANE);POLYDIMETHYLSILOXANE;BEHAVIOR;PROPERTY;ESCA