Optically active conjugated polymer from solvent chirality transfer polymerization in monoterpenes.
Disubstituted acetylene monomers [1,2-diphenylacetylenes (DPAs: DPA-pC1, DPA-mC1, DPA-pC8); 1-phenyl-2-hexylacetylene (PHA-pC1)] are tested for asymmetric polymerization in chiral monoterpenes used as solvents and compared with the corresponding monosubstituted acetylene monomer [1-phenylacetylene (PA-pC1)]. DPA-pC1 containing a trimethylsilyl group in the para-position of the phenyl ring produces an optically active polymer with a large Cotton effect, despite the absence of a stereogenic center. The polymer sample obtained by polymerization in 87% ee (-)-α-pinene shows the strongest CD signal (gCD value at 385 nm: ∼3.2 × 10⁻³). The Cotton bands of the polymers obtained in (-)- and (+)-α-pinenes show the opposite sign in the CD signals. Theoretical calculations show that only the cis-cisoid model adopts a helical conformation. A time-correlated single photon counting experiment shows that the emission of the chiral polymer originates from a virtually single excited species with a 98% component fraction. This polymer solution does not show any significant decrease in gCD value over a wide temperature range of 20 to 80 °C. No noticeable decrease in the gCD value is detected when the polymer solution is kept at relatively low temperatures for a prolonged period (35 d). In contrast, the other polymers show no CD signal.
Department of Polymer Science, Kyungpook National University, 1370 Sankyuk-dong, Buk-ku, Daegu, 702-701, Korea; Daegu Technopark Nano Convergence Practical Application Center, 891-5 Daecheon-dong, Dalseo-ku, Daegu, 704-801, Korea.
Hyojin
H
Kim
Daehoon
D
Lee
Seul
S
Lee
Nozomu
N
Suzuki
Michiya
M
Fujiki
Chang-Lyoul
CL
Lee
Giseop
G
Kwak
D000114:Acetylene / Q000031:analogs & derivatives; D002942:Circular Dichroism; D008968:Molecular Conformation; D039821:Monoterpenes / Q000737:chemistry*; D058105:Polymerization; D011108:Polymers / Q000737:chemistry*; D012997:Solvents; D013237:Stereoisomerism
D039821:Monoterpenes; D011108:Polymers; D012997:Solvents; C044736:phenylacetylene; D000114:Acetylene
chirality transfer; conjugated polymer; monoterpene; optical activity; stack structure