Photorefractivity in nematic liquid crystals doped with a conjugated polymer: Mechanisms for enhanced charge transport
- Argonne National Lab., IL (United States). Chemistry Div.
New organic materials that exhibit photorefractive effects are of wide interest for potential optical signal processing applications. The authors report on a photorefractive nematic liquid crystal composite containing the conjugated polymer poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene), BEH-PPV that exhibits a novel fringe spacing dependent inversion of the polarity of the space-charge field due to competition between the ionic diffusion and charge drift transport mechanisms. A eutectic mixture of 35% (wt %) 4{prime}-(n-octyloxy)-4-cyanobiphenyl, 8OCB, and 65% 4{prime}(n-pentyl)-4-cyanobiphenyl, 5CB, was doped with 10{sup {minus}5} M BEH-PPV (200 kD by GPC), as the electron donor. The molecular weight of the BEH-PPV polymer implies that 500 repeat units of the monomer are present with an extended chain length of 0.35 {micro}m. N,N{prime}-Dioctyl-1,4:5,8-naphthalenediimide, NI, 8 {times} 10{sup {minus}3} M, was added as the electron acceptor. The free energy change for the photoinduced electron-transfer reaction, (BEH-PPV) + NI {yields} (BEH-PPV){sup +} + NI{sup {minus}}, is {minus}1.0 eV. Two other liquid-crystal composites were also studied as controls.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Office of Naval Research, Washington, DC (United States)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 682127
- Journal Information:
- Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 6 Vol. 11; ISSN CMATEX; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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