Abstract :
As part of a continuing effort to effect the chemical modification of
fluorocarbon polymers, we have been engaged in the examination of
substitution reactions of poly(chlorotrifluoroethylene) (PCTFE).
Previous efforts by ourselves and others have shown that two electron
reduction processes generally proceed through elimination and on to
other side reactions, while one electron processes can sometimes be
trapped to afford a clean substitution of trapping agent for
chloride, often to rather large degrees of functionalization.
We were intrigued by the prospect of using oxidative addition
processes to effect substitution reactions on PCTFE. Examination of
the literature indicated that perfluorocarbon ligands bound to
transition metals were not particularly prone to elimination, but
that oxidative addition to a carbon-chlorine bond (rather than the
weaker bonds from carbon to iodine or bromine) was not well known. As
a result, we undertook a study of the reactions of metal carbonyl
complexes with PCTFE, in the forms of KelF 6061 (3M) and Neoflon
M400H (Daikin).
Reaction of PCTFE with anionic metal carbonyls (Na2Fe(CO)4, etc.) leads to extensive
elimination along the polymer backbone, as indicated by IR analysis
as well as discoloration of the bulk material. Reaction with Group 6
metal carbonyl species (chromium hexacarbonyl, as well as the
molybdenum and tungsten analogues) in DMF at 90C leads to formation
of the acyl metal species, with subsequent addition of an external
nucleophile and isolation of the acid derivative. PCTFE derivatized
by carboxylic acid and amide functional groups are isolated with
minimal side reaction.
All of the above species are characterized by FT-IR and elemental
analysis. The carboxylate is additionally characterized by
titrimetric analysis and scanning electron microscopy. A depth
profile is reported by means of ATR-FT-IR and examination of attempts
to trap the perfluoroalkyl metal species before carbonyl migration
are outlined.
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