Synthesis and Characterization of Diastereoisomeric Polyesters Derived from Bisphenols Bearing Vicinal Trifluoromethyl Groups

Several
diastereoisomeric polyesters bearing vicinal stereogenic
centers in the backbone were synthesized to investigate the influence
of diastereoisomerism on the properties of polymers. To hamper the
free rotation of the Csp3–Csp3 single bond between the stereogenic centers, bisphenol
monomers containing vicinal CF3 moieties were designed
and synthesized, wherein the CF3 group acts not only as
a conformational stabilizer but also as a probe to provide information
on stereoconfiguration. X-ray single-crystal structure and density
functional theory (DFT) calculations indicate that the antimonomer
tends to adopt a linear and extended configuration, whereas the most
stable conformation for its diastereoisomer is kinked. These geometries
resemble those possessed by the E and Z 1,2-disubstituted alkenes. The polymers based on these isomeric
monomers display distinct glass transition state temperature (Tg), crystallinities, mesoscopic morphology,
and hydrophobicity, which can be attributed to the different polymer
chain arrangement in the solid state. These observations support our
hypothesis to utilize aliphatic moieties bearing vicinal stereogenic
centers to mimic the geometry of the E and Z olefinic units, which serves as a new strategy to finely
tune the polymer performance.