NOVELTY - A composition comprises an organic material which is susceptible to oxidative, thermal or light-induced degradation; and a S-perfluoroalkyl substituted hydroxybenzylthioether derivative (I) (excluding 2,4-dimethyl-6-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octylsulfanylmethyl)-phenol, and 2,4-dimethyl-6-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octane-1-sulfinylmethyl)-phenol), where the composition does not contain a compound with a perfluorinated substituent other than that of compound (I).    USE - For reducing the surface energy of organic materials; and for imparting oil and water repellency to the organic material (claimed); in preparation of: floating devices, marine applications, pontoons, buoys, plastic lumber for decks, piers, boats, kayaks, oars, and beach reinforcements; automotive applications e.g. bumpers, dashboards, battery, hat shelf, air bag covers, headlamp glass, door panels, and fuel pumps; road traffic devices e.g. sign postings, posts for road marking, warning triangles, helmets and tires; devices for plane, railway, motor car including furnishings; devices for space applications, e.g. rockets and satellites; devices for architecture and design, mining applications, acoustic quietized systems, street refuges, and shelters; appliances, cases and coverings in general and electric/electronic devices (e.g. personal computer), and flower pots; jacketing for e.g. steel or textiles; devices for the electronic industry, e.g. insulation for plugs, cases for electric and electronic parts, and materials for electronic data storage; electric appliances e.g. washing machines, ovens and irons; covers for lights; applications in wire and cable (semi-conductor, insulation and cable-jacketing); foils for e.g. condensers, refrigerators, air conditioners; technical articles e.g. cogwheel (gear), slide fittings; rotor blades, ventilators and windmill vanes, solar devices and swimming pool covers; sanitary articles e.g. sinks; hygienic articles e.g. diapers, feminine hygiene articles, brushes, mobile toilets; pipes; profiles of any geometry (window panes) and siding; glass substitutes e.g. extruded plates, glazing for buildings, aircraft, train and transportation; plates, extrusion-coating; Cement-, concrete-, composite-applications and covers, siding and cladding; woven fabrics; membranes, insulation, covers and seals for e.g. roofs, tunnels, dumps, and walls roofing membranes; films (packaging, dump, laminating, agriculture and horticulture, greenhouse, mulch, tunnel, silage); food packing and wrapping; storage systems such as boxes and luggage; cartridges, syringes, medical applications; Support devices e.g. sports and fitness devices; furniture in general e.g. foamed articles; materials for optical and magnetic data storage; kitchen ware; boxes for e.g. cassettes and video tapes; footwear; and devices of filled polymers and wollastonite.    ADVANTAGE - The composition does not contain a compound with a perfluorinated substituent other than that of the compound (I).    DETAILED DESCRIPTION - A composition comprises an organic material which is susceptible to oxidative, thermal or light-induced degradation; and a S-perfluoroalkyl substituted hydroxybenzylthioether derivative of formula (I) (excluding 2,4-dimethyl-6-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octylsulfanylmethyl)-phenol, and 2,4-dimethyl-6-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octane-1-sulfinylmethyl)-phenol), where the composition does not contain a compound with a perfluorinated substituent other than that of compound (I).    R1=G1, G2, or G3;    G1=H, 1-25C alkyl, 2-25C alkenyl, -CO-R5, -CH(R10)CO-R5, -C(R10)2CO-R5, -CO-N(R6)-R7, -CH(R10)CO-N(R6)-R7, -C(R10)2CO-N(R6)-R7, or -CH(R10)COOR5;    G2=1-24C alkylene (optionally substituted by 1-4C alkyl, benzyl or phenyl), 2-24C alkylene, (optionally interrupted by oxygen or sulfur), -CO-R8-CO-, -CH(R10)CO-R8-CO-CH(R10)-, -C(R10)2CO-R8-CO-C(R10)2-, -CO-N(R6)-R9-N(R6)-CO-, -CH(R10)CO-N(R6)-R9-N(R6)-CO-CH(R10)-, -C(R10)2CO-N(R6)-R9-N(R6)-CO-C(R10)2-, -CH(R10)CO-O-R9-O-CO-CH(R10)- or -C(R10)2CO-O-R9-O-CO-C(R10)2-;    G3=1-(3,5-diacetyl-phenyl)-ethanone;    R2-R4=H, 1-25C alkyl, 2-25C alkenyl, -CH(R11)-S(O)p-R12, group of formulae (i)-(iii);    R5=phenyl (optionally substituted by 1-4C alkyl or halo), 1-25C alkyl, 2-25C alkenyl, or 7-12C phenylalkyl;    R6=H or 1-4C alkyl;    R7=phenyl (optionally substituted by 1-4C alkyl or halo), H, or 1-25C alkyl;    R8=1-24C alkylene (optionally substituted by 1-4C alkyl, benzyl or phenyl), phenylene, or 2-24C alkylene (optionally interrupted by oxygen or sulfur);    R9=direct bond, 2-24C alkylene (optionally substituted by 1-4C alkyl, benzyl or phenyl), 2-24C alkylene (optionally interrupted by oxygen or sulfur);    R10=H or 1-8C alkyl;    R11=H, 1-8C alkyl, or phenyl (optionally substituted by 1-4C alkyl);    R12=monovalent linear or branched organic radical containing perfluorinated alkyl having 6 fully fluorinated carbon atoms;    R13=H, 1-25c alkyl, 2-25C alkenyl, -CO-R5, -CO-N(R6)-R7 or -CH2-CO-N(R6)-R7;    R14 and R15=H, 1-25C alkyl, 2-25C alkenyl or -CH(R11)-S(O )p-R12;    R16=methylene (optionally substituted by 1-4C alkyl), -S-, -S(O)-, -S(O)2- or -CO-;    R17=1-4C alkyl;    n=1-3;    p=0-2.    Provided that:    (1) when n is 1, then R1 is G1;    (2) when n is 2, then R1 is G2;    (3) when n is 3, then R1 is G3;    (4) at least one of the radicals R2-R4 is -CH(R11)-S(O)p-R12.