Synthesis and surface characterization of novel perfluorooctyl-functionalized polymers with well-defined architectures

We have successfully synthesized two kinds of novel well-defined chain-end-functionalized polystyrenes with one, two, three, and four perfluorooctyl (C₈F₁₇) groups and structurally analogous block copolymers, poly[styrene-b-4-(3-perfluoroocyl)propoxystyrene], by means of living anionic polymerization, followed by the Williamson reaction with C₈F₁₇(CH₂)₃Br. The surface properties and compositions of the films prepared from both C₈F₁₇-functionalized polymers have been characterized by contact angles using water and dodecane droplets and angle-dependent XPS measurement. It was observed that C₈F₁₇ groups were segregated and preferentially enriched at their topmost surfaces and the extent of the enrichment increased with the number of C₈F₁₇ group. The dependence of extent of C₈F₁₇ group enrichment on fluorine content however appears to be different between chain-end-functionalized polymer and block copolymer.     

Intramolecular ring opening of a 2,3-epoxy alcohol by a xanthate anionic center; stereospecific preparation of 2-mercapto-1,3-diol units

Stereospecific ring openings of optically active 2,3-epoxy alcohols were performed by the reaction of 1 , 3 , 5 , and 7 with carbon disulfide and sodium hydride to give the five-membered xanthates 2 , 4 , 6 , and 8 . Both enantiomers of 2-mercapto-1,3-diol triacetates, 11 and 14 , were derived from 4 and 6 , respectively. The ring opening reaction proceeded at −78°C to −30°C, and the yields were around 80%. However, at a higher temperature between 0°C to room temperature, a complicated reaction took place and led to the formation of two isomers of the cyclic thiol carbonates 15 and 16 from 1 or 5 . These processes were also stereospecific, and mechanisms have been proposed. In the case of the 3,4-epoxy alcohol 20 , the epoxide ring opening gave the six-membered xanthate 21 stereospecifically.