Synthesis of alpha,omega-bis epoxy oligo (1 ' H,1 ' H,2 ' H,2 ' H-perfluoroalkyl siloxane)s and properties of their photo-acid cross-linked films
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Low-viscosity oligomers 1,9-bis[2 -(4-cyclohexenyl-1,2-epoxy)ethyl]-1,1,3,5,7,9,9-heptamethyl-3,5, 7-tris(1H,1H,2H,2H-perfluorooctyl)pentasiloxane (VII), 1,9-bis[2 -(4-cyclohexenyl-1,2-epoxy)ethyl]-1,1,3,5,7,9,9-heptamethyl-3,5,7-tris(3, 3,3-trifluoropropyl)pentasiloxane (VIII), and 1,9-bis[2 -(4-cyclohexenyl-1,2-epoxy)ethyl]decamethylpentasiloxane (IX) have been prepared by Pt-catalyzed hydrosilylation reactions of 4-vinylcyclohexene-1,2-epoxide with 1,9-dihydrido-1,1,3,5,7,9,9-heptamethyl-3,5,7-tris(1H,1H, 2H,2H-perfluorooctyl)pentasiloxane (IV), 1,9-dihydrido-1,1,3,5,7,9,9-heptamethyl-3,5,7-tris(3,3, 3-trifluoropropyl)pentasiloxane (V), and 1,9-dihydridodecamethylpentasiloxane (VI), respectively. IV-VI were prepared by the triflic-acid-catalyzed ring-opening of 1,3,5-trimethyl-1,3,5-tris(1H, 1H,2H,2H-perfluorooctyl)cyclotrisiloxane (I), 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl) cyclotrisiloxane (II), and hexamethylcyclotrisiloxane (D3) (III), respectively, in 1,1,3,3-tetramethyldisiloxane (TMDS). Solutions of a UV-sensitive diaryliodonium salt (0.5 wt %) and oligomers VII-IX were cast as uniform layers onto clean glass microscope slides and steel coupons. UV irradiation of these liquid layers rapidly converted them to cross-linked films (X-XII). Thermal stability of these films was determined by thermogravimetric analysis (TGA). Glass transition temperatures (Tgs) were measured by dynamic mechanical thermal analysis (DMTA). Static contact angles of distilled water on the air-film interfaces of X-XII have been determined with a goniometer. Dynamic contact angle (DCA) measurements have also been carried out on free-standing films. Corrosion protection of steel coupons by X-XII was evaluated by electrochemical impedance spectroscopy (EIS) during exposure to 0. 5 N NaCl. Antifoul and foul-release properties of X-XII were studied by settlement and removal tests with the barnacle Balanus amphitrite and with spores and sporelings of the green alga Enteromorpha.