Prearranged Luminescence

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Science  07 Jul 2006:
Vol. 313, Issue 5783, pp. 20
DOI: 10.1126/science.313.5783.20c

Conjugated organic polymers such as poly(p-phenylenevinylene) (PPV) have attracted interest for use in sensors, light-emitting diodes, and other electronic applications. One advantage of these materials is their facile processability; for example, films can be fabricated under mild conditions by spin-casting from solution.

Satrijo et al. show that a judicious choice of solvent for the spin-casting process can influence the structural and electronic properties of the resultant films. They studied the absorption and luminescence spectra of films prepared from a PPV derivative modified with chiral alkyl-substituted hydroquinone side chains. Films cast from chloroform, in which the polymer was highly soluble, were disordered but adopted an M-configured helical arrangement on annealing, as revealed from the circular dichroism spectrum and detection of right circularly polarized luminescence. When 1,2-dichloroethane (DCE) was used as the solvent, unannealed films emitted left circularly polarized luminescence, indicative of a kinetically stable, oppositely configured P helical structure. Spectra of the DCE solution before spin-casting supported self-assembly of helical aggregates that conserved their configuration during casting. By adding acetonitrile to the original chloroform solutions, the authors could induce complementary solution-phase aggregation, leading to right circularly polarized luminescence on irradiation. — JSY

J. Am. Chem. Soc. 128, 10.1021/ja063027c (2006).

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