FUNCTIONALIZATION AND METALLIZATION OF FLUOROPOLYMER SURFACES THROUGHREDUCTION

Fluoropolymer films, such as Teflon(TM)-TFE [poly(tetrafluoroethylene) ], Teflon(TM)-FEP [copolymer of tetrafluoroethylene and hexafluoroprop ylene], Teflon(TM)-PFA [copolymer of tetrafluoroethylene and perfluoro (propyl vinyl ether)], and PCTFE [poly(chlorotrifluoroethylene)], are reduced by the mild reducing agent benzoin dianion/DMSO, while Teflon( TM)-AF [copolymer of tetrafluoroethylene and perfluoro-2,2-dimethyl-1, 3-dioxole] is unreactive. The reduction makes the films adherable towa rd epoxy resins, the adhesive strength decreasing in the order PCTFE > PFA greater than or equal to FEP > PTFE. Surprisingly, Teflon(TM)-AF films are totally inert except when the TFE content is high, and in th ese cases, the adhesive strength of Teflon(TM)-AF is close to that of PTFE. The surfaces of PTFE, FEP and PFA films are further modified by first treating these films with the benzoin dianion/DMSO reagent and t hen with an excess of sodium salts of mercaptans. Reactive PTFE films that are light colored with a metallic luster are formed rather than t he dark, metallic color typical of PTFE surface reduction without merc aptan treatment. These films have poor adhesion toward epoxy resins bu t good adhesion toward gold applied by sputtering. FEP and PFA films b ehaved similarly. These results are attributed to the incorporation of sulfur onto the reduced surface. Unreduced fluoropolymer films reacte d with only sodium mercaptan fail to show C-S bond incorporation. This newly developed method can be used to selectively metallize the fluor opolymer film surface with gold layers and affords very high conductiv ity of the metallized regions. (C) 1995 John Wiley and Sons, Inc.