Water and oil repellency of polysiloxanes with highly fluorinated alkyl side chains

A series of fluorinated polysiloxanes (FLSs) with the 3,3,4,4,5,5,6,6,6-nonafluorohexyl group (C4F9C2H4), 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecyl group (C8F17C3H6), 3-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanamido) propyl group [HDFNAG; C8F17(CO)NHC3H6], and 3-(N-methyl-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanamido) propyl group [C8F17(CO)N(CH3)C3H6] were synthesized. Their homopolymers (homo-FLSs) and copolymers with dimethylsiloxane (co-FLSs) were included. The polyester fabrics were treated with these FLSs, and their water and oil repellency was evaluated. These fabrics showed a moderate to good level of water repellency but a poor to zero level of oil repellency, except for those fabrics treated with homo-FLSs with HDFNAG. The characterization of the surface chemical composition by X-ray photoelectron spectroscopy showed that the concentration of fluorine at the surface was not particularly high for poly(ethylene terephthalate) films treated with homo-FLSs with HDFNAG. Differential scanning calorimetry measurements of these FLSs revealed that only homo-FLSs with HDFNAG had a high melting temperature of 75.7°C. These two measurements suggested that the reason the fabrics treated with homo-FLSs with HDFNAG showed good oil repellency was not because the concentration of fluorine at the surface was much higher than for the others but because the reorientation of HDFNAG did not take place for its packing after contact with oil. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1085–1091, 2003