A homologous series of shape-persistent V-shaped molecules has been designed to form the biaxial nematic phase. Phenyleneethynylene moieties are attached to a bent fluorenone unit to create an apex angle of about 90°, which is determined from the single crystal structure. Two mesogens, one symmetric and another unsymmetric, have been synthesized by attaching a cyano group to one or both of the peripheral phenyl units, respectively. These groups introduce local dipoles essential for the formation of the nematic phases. The tendency to form a crystalline phase is reduced by laterally substituted hexyloxy chains which allow the nematic phase to be supercooled to a glassy state. Two of the three fluorenone derivatives exhibit a transition from the uniaxial nematic to the biaxial nematic phase. This transition has an undetectably small transition enthalpy, but the X-ray diffraction, polarizing optical microscopy, and conoscopy reveal the presence of the biaxial order in the low temperature nematic phase.
Three new topology-varied rod-coilblockcopolymers, comprising the same oligo(p-phenyleneethynylene) (OPE) rod components and the same coil components, were synthesized by atom-transfer radical polymerization. Their photophysical properties were systematically studied and compared in consideration of their solid-state structures and self-assembly abilities. These copolymers have similar intrinsic photophysical
A series of biaxial V-shaped, shape-persistent molecules has been synthesised by stepwise coupling of phenylene ethynylene arms to an oxadiazole bending unit. Studies of their thermotropic nematic phases point to phase biaxiality.
Synthesis of linear and V-shaped oligo(phenylene ethynylene) derivatives: Geometric effects on photophysical properties
作者:Si Chun Yuan、Shu Liang Han、Xing Ge、Hui Chuan Wang
DOI:10.1016/j.cclet.2009.08.013
日期:2010.1
A series of linear and V-shaped oligo(phenylene ethynylene) derivatives 1–3 were synthesized through sequent Sonogashira coupling and propargyl alcohol deprotection reaction in high yields. The alkoxy chains (i.e., n-hexyloxy groups) were introduced to assure good solubility of compounds 1–3 in common solvents. The photophysical properties of 1–3 in solution depend strongly on the geometries of these
Oligo(<i>p</i>-phenyleneethynylene)-functionalized Perylenebisimidetriad: Synthesis, Photophysical Properties, and Self-assembly
作者:Weiqi Tong、Wei Wei、Haibo Chen、Hongyu Wang
DOI:10.1002/cjoc.201200858
日期:2013.2
The rod‐like oligo(p‐phenylene ethynylene)‐functionalizedperylenebisimide triad was synthesized and characterized. Aggregation behavior in solvents of different polarity was investigated by absorption and fluorescent spectroscopy. The results showed that stronger aggregations took place in low‐polarity slovent. The experiments also indicated that the energy and electron transfer might takeplace between