Uniaxial alignment of liquid-crystalline conjugated polymers by nanoconfinement.
We demonstrate the uniaxial alignment of a liquid-crystalline conjugated polymer, poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) by means of nanoconfinement during nanoimprinting. The orientation of the conjugated backbones was parallel to the nanolines imprinted into the polymer film. Polarized UV-vis absorption and photoluminescence spectra were measured to quantify the degree of alignment, showing that the polarization ratio and uniaxial molecular order parameter were as high as 66 and 0.97, respectively. The aligned F8BT film was used as the active layer in a PLED, which resulted in polarized electroluminescence with a polarization ratio of 11. Ambipolar PFET in a top-gate configuration with aligned F8BT as the active semiconducting layer showed mobility enhancement when the chains were aligned parallel to the transport direction. Mobility anisotropies for hole and electron transport were 10-15 and 5-7, respectively, for current flow parallel and perpendicular to the alignment direction.
Zheng
Zijian
Z
Melville Laboratory for Polymer Synthesis, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Yim
Keng-Hoong
KH
Saifullah
Mohammad S M
MS
Welland
Mark E
ME
Friend
Richard H
RH
Kim
Ji-Seon
JS
Huck
Wilhelm T S
WT
D016880:Anisotropy; D052160:Benzothiazoles / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D004553:Electric Conductivity; D005449:Fluorenes / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D012666:Semiconductors; D013499:Surface Properties
D052160:Benzothiazoles; D005449:Fluorenes; D046911:Macromolecular Substances; D011108:Polymers; C505505:poly(9,9-di-n-octylfluorene-alt-benzothiadiazole)