Structural Studies of Semifluorinated n-Alkanes. 3. Synthesis and Characterization of F(CF₂)_n(CH₂)_m(CF₂)_nF

A series of semifluorinated triblock oligomers of the form F(CF2)n(CH2)m(CF2)nF(FnHmFninour notation) have been synthesized and characterized by thermal analysis and low-frequency Raman measurements. Only a single endothermis observed for the series of F12HmF12 (6 ≤ m ≤ 22) molecules corresponding to the crystalline melting point. In the limit of vanishing m, the melting point of F(CF2)24F has been predicted by extrapolation and compared with that which recently appeared in the literature. Low-frequency (30-330 cm-1) Raman measurements revealed the presence of two bands attributable to the longitudinal acoustical mode oscillations (LAM) of the extended molecule. © 1988, American Chemical Society. All rights reserved.