Main‐Chain Liquid Crystalline Polymers Based on Bis‐Etherified 9,9‐Dihexyl‐2,7‐bis(4′‐hydroxy‐1,1′‐biphen‐4‐yl)fluorenes

Abstract

A series of liquid crystalline compounds based on 2,7‐bis(biphenyl)fluorenes was synthesised by a Suzuki cross‐coupling reaction and subsequent etherification with different bromoalkenes. By simple variations of the chain lengths the temperature range in which the nematic mesophase is present could be tuned. The described approach offers the possibility of covalent incorporation of the mesogens into polymers via olefin metathesis techniques, resulting in enlarged stability of the mesophase. Monomers and polymers could be easily aligned on rubbed polyimide substrates as revealed by polarised absorption spectroscopy.

ADMET: Metathesis polycondensation

“…Multiple areas beyond those mentioned thus far include ADMET‐derived liquid crystalline and conjugated systems 110. Most recently, main‐chain ADMET liquid crystalline structures have been of interest in designing materials for electromechanical actuators111 and nonlinear optic in display technologies 112–114. Further research in display technologies has been accomplished in conjugated systems.…”

Phosphorescent Organic Light-Emitting Devices: Working Principle and Iridium Based Emitter Materials

“…the generation of light by electrical excitation of an organic material) in the 1960s by applying hundreds of volts to an anthracene single crystal [ 1 ], in the recent decades the field of organic electronics has progressed enormously [ 2 ]. Boosted by the pioneering work of Tang and VanSlyke and the resulting worldwide activity in numerous research groups [ 3 ], the advances in the fields of device science, device fabrication as well as chemistry, physics and materials science have evolved organic light-emitting device (OLED) technology to a point where it is now an important competitor to liquid crystals and liquid crystal displays (LCDs) [ 4 – 8 ]. Consequently, the interest in OLED technology has been impressive and first commercial products based on small molecules and conducting polymer films are already available.…”

Defect chemistry of polyfluorenes: identification of the origin of “interface defects” in polyfluorene based light-emitting devices

“…Among the wide variety of conjugated polymers suitable for application in polymeric light-emitting devices (PLEDs), polyfluorenes (PFs) have undoubtedly emerged as one of the most promising candidates for realizing blue electroluminescent devices. [1][2][3][4][5] However, investigations on the electroluminescent properties of polyfluorenes identified degradation processes during device operation (accompanied by the occurrence of a green emission band at 2.2 to 2.3 eV) as a critical drawback for practical applications. [6][7][8][9] Not surprisingly, numerous research activities focused on this topic controversially discussing aggregates and excimers [10][11][12][13][14] as well as chemical defects (i.e., ketonic defect sites) [8][9]15 as the potential origin of the low-energy emission band.…”

“…Scheme 1b). 22 Furthermore, 9,9-dihexyl-2,7-bis(4 0 -hydroxy-1,1 0 -biphen-4-yl)fluorene (2) and its monoetherified analogue (3) were synthesized following the procedure of Sovic´et al 4 to investigate deprotonation effects on simplified model compounds (cf. Scheme 1b).…”