Cyclotetrasiloxane, 2,4,6,8-tetramethyl-2-[3-[2,3,3,3-tetrafluoro-2-[1,1,2,3,3,3-hexafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)propoxy]propoxy]propyl]-, Si-[3-(2-oxiranylmethoxy)propyl] derivs.