Hits:

Date of Publication:2008-01-01

Journal:高分子学报

Issue:9

Page Number:874-879

ISSN No.:1000-3304

Abstract:Fluorinated organic-Inorganic hybrid materials were prepared using fluorine-containing monomers, silicone-containing monomers and tetraethyl orthosilicate by free-radical random copolymerization and sol-gel process, and applied as functional coatings onto aluminium alloy substrates. The fluorine-containing monomer used was dodecafluoroheptyl methyl acrylate (FA), and silicone-containing monomer used was vinyltriethoxy silane (VTES). Tetraethyl orthosilicate (TEOS) was added to pre-polymerized FA-co-VTES (PFAS) solution to cohydrolyze and co-condense with different addition values. The influence of inorganic component content (TEOS) on the physical properties of the coating films were characterized by FTIR, TGA, GPC, SEM, and XPS. The surface free energies of fluorinated organic-inorganic hybrid materials prepared were estimated from the contact angle data measured by sessile-drop method. Transparent coating films with smooth surface and uniform thickness could be obtained by the dip coating technique. FTIR and XPS results indicated that, owing to the strong electronegativity of the fluorine atoms, hydrophobic perfluoroalkyl groups were preferentially enriched to the outermost layer at the coating film-air interface, and three layers probably existed in the coating film. The upper layer oriented toward the air was composed of mainly perfluoroalkyl groups originating from FA, the intermediate layer was composed of hydrocarbon backbone chain originating from vinyl polymerization, and the bottom layer was composed of mainly -O-Si-O- network originating from TEOS. The fluorinated organic-inorganic hybrid materials prepared were very hydrophobic and exhibited excellent water repellency. It was demonstrated that the water repellency properties of PFAS/SiO2 hybrid materials was governed by hydrophobic perfluoroalkyl groups of the outermost layer. The contact angles of the coating films for water and methylene iodide were extremely high, at 120. 9 degrees and 93 degrees, respectively, for TEOS/FA mole ratios at 1 : 1, and their surface free energies were about 11.48 mJ/m(2). An important role of tetraethyl orthosilicate (TEOS) was to increase the density of the reaction sites of the -OH groups with the surface area and the thickness of fluorinated organic-inorganic hybrid coatings. It has been confirmed by FTIR and GPC results that the increase of TEOS amounts could enhance hydrolysis and condensation of alkoxide precursors to improve the adhesion between hybrid coating and aluminum substrates by the formation of Si-O-Al bonds. It was also testified that the increase of inorganic silica content had a significant effect oil the improvement of thickness of the bottom SiO2 layer, while it had a slight influence on the surface wettability of the hybrid coatings. The useful properties of fluorinated organic-inorganic hybrid coatings like better thermal stability and improved corrosion resistance,could be significantly enhanced by the improvement of thickness of the bottom SiO2 layer and bonding between SiO2 layer and aluminum substrates. Morphology analysis by SEM showed that the introduction of flexible organic phase could relax the stress and reduce the microcracks caused by the volume shrinkage of silicon network during heat treatment process. The thermal stability of fluorinated organic-inorganic hybrid materials studied by using TGA technique could be improved with TEOS amounts.
   The burning temperature should be less than 290 degrees C because the perfluoroalkyl groups begin to decompose from this temerature.

Note:新增回溯数据