Unsaturated perfluoroalkyl esters derived from undecylenic acid : CH2=CH-(CH2)8-COO-CH2-CH2-R(F) (with R(F) = C6F13, 2a and R(F) = C8F17, 2b) and C8F17-(CH2)10-COO-CH2-CH=CH2, 2c were prepared with excellent yields. Their hydrosilylation by methylhydrodimethylsiloxane copolymers of various Si - H contents gives new fluorinated polysiloxanes which were examined by H-1- and C-13-NMR, GPC, differential scanning calorimetry, and optical polarizing microscopy. Polymers derived from compounds 2a and 2b exhibit mesomorphic structures.