SURFACE PROPERTIES OF PARTIALLY FLUORINATED EPOXY-BASED NETWORKS

ELISABETH PENOFF; ALEJANDRO MICCIO; ROCIO LIAÑO; CRISTINA HOPPE; P.E. MONTEMARTINI; P.A. OYANGUREN

San José

Congreso; X Congreso Iberoamericano de Polímeros; 2010

Functionalizacion of epoxy-based networks to achieve materials with high hydrophobicity is described by employing two strategies: a) preferential surface enrichment of perfluorinated tails linked the network precursors [1], and b) incorporation of fluorocarbon-coated silver nanoparticles. The selected fluorinated epoxies (FE) were: 2,2, 3,3,4,4,5,5,6,6,7,7,8,9,9,9-hexadecafluoro-8-trifluoro methyl nonyloxirane (FED3) and 2,2,3,3,4,4,5,5, 6,6,7,7-dodecafluoroheptyl ether (FES3). Several series of crosslinked fluorinated epoxy-based materials containing variable fluorine contents (from 0 to 6 wt % F) were prepared using formulations based on partially fluorinated diamine, epoxy monomer and a curing agent. The epoxy monomer was based on diglycidyl ether of bisphenol A (DGEBA) while the curing agents were either propyleneoxide diamine (Jeffamine), 4,4'-Methylenebis(2,6-diethylaniline) (MCDEA) or 4,4´-methylene bis(3-chloro 2,6-diethylaniline) (MDEA). Silver nanoparticles were synthesized at room temperature from an aqueous/acetone silver ion solution using (C8H17)4NBr as phase transfer catalyst [2]. A thiolated fluorocarbon molecule, 1H,1H,2H,2H-perfluoro decanethiol was used as the stabilizing ligand. After stirring overnight, the capped silver nanoparticles flocculated in the water/acetone solution. They were separated by centrifugation and redispersed in pure acetone. The influence on thermal and surface properties of the architecture of FE, and the molecular structure of the unit building blocks was analyzed and discussed. It was found that all the series showed high hydrophobicity and oleophobicity, independently of the crosslink density, bulk composition, and curing conditions. The homogeneity of final materials depends on the curing agent employed. Samples cured with Jeffamine are homogeneous while the ones cured with MCDEA show phase separation process during polymerization. The surface properties and composition of the samples were analyzed using static contact angle measurements and XPS. As an example, figure 1 shows the experimental results of the air side corresponding to the series prepared with Jeffamine and MCDEA with variable fluorine concentration. XPS measurements showed a surface composition much richer in fluorinated segments than expected from bulk composition. Fluorine enrichment was also manifested at the polymer/aluminum interface. This observation is discussed in terms of the molecular weight dependence of surface tension and configurational entropy of the thermosetting matrix.