Partially fluorinated polymer networks: Synthesis and structural characterization

Abstract

Functionalizacion of epoxy-based networks by the preferential surface enrichment of perfluorinated tails to achieve hydrophobic surface is described. The selected fluorinated epoxies (FE) were: 2,2,3,3,4,4,5,5,6,6,7,7,8,9,9,9-hexadecafluoro-8-trifluoromethyl nonyloxirane (FED3) and 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluoro nonyloxirane (FES3). Two series of crosslinked fluorinated epoxy-based materials containing variable fluorine contents (from 0 to 5 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) or 4,4′-methylenebis(3-chloro 2,6-diethylaniline) (MCDEA). It was found that depending on the curing agent employed, homogeneous distribution of fluorine or phase separation distinguishable at micrometer or nanometer scale was obtained when curing blends initially homogeneous. The morphology and composition of partially fluorinated networks were investigated on a micrometer scale combining scanning electron microscopy and X-ray analysis. When curing with JEFFAMINE, samples were homogeneous for all fluorine proportions. In contrast, MCDEA-cured blends showed fluorine-rich zones dispersed in a continuous epoxy-rich phase. A completely different morphology, characterized by a distribution of irregular fluorine-rich domains dispersed in an epoxy-rich phase, was obtained when curing blends initially immiscible.