END GROUP CHEMISTRY OF FLUORO-OLIGOMERS - HIGHLY SELECTIVE SYNTHESES OF DIEPOXY, DIALLYL, AND TETRAOL DERIVATIVES

Different synthetic methods for the preparation of polyfunctional fluo rinated oligomers were explored and the results compared. Fluoropolyet her macromonomers bearing epoxy, allyl, and polyhydroxy end groups wer e synthesized and spectroscopically characterized. For obtaining a pol yol (namely tetraol) functionality, a highly selective route was the r eaction of the fluoropolyether macrodiol ZDOL with allylic halides and subsequent oxidation reaction at the C=C double bond by means of pero xyacids. This approach made it possible to obtain a segmented structur e RH-RF-RH in which the molecular body RF consisted of a perfluoropoly ether block endcapped by two hydrogenated segments RH, where RH = - CH 2OCH2CH(OH)CH2OH. Unlike other more conventional syntheses, which alwa ys produce byproducts and higher molecular weight species such as RH-( RF-RH)(n)-RF-RH or RH-RF-(RH)(n)-, the described method offers high yi elds and selectivity. The fluoropolyether polyfunctional derivatives o ffer the possibility to prepare a variety of highly crosslinked fluori nated materials and, owing to their well defined regularly segmented s tructures, they also constitute interesting models for the understandi ng of basic structure-property relations of fluoro-oligomers and their copolymers. (C) 1996 John Wiley & Sons, Inc.