To investigate the vacuum-deposited films of the banana-shaped mesogens, we prepared a three-ring bent-core (that is, banana-shaped) compound m-bis(4-p- octoxysryrenyl)benzene (m-OSB) and used it as a prototype for st...To investigate the vacuum-deposited films of the banana-shaped mesogens, we prepared a three-ring bent-core (that is, banana-shaped) compound m-bis(4-p- octoxysryrenyl)benzene (m-OSB) and used it as a prototype for studying the related film physics. Herein the synthesis and the structural characterization of m-OSB are reported. 13C and 1H NMR spectra and IR spectrum confirm that m-OSB has a symmetric and all-trans conformation. The results of differential scanning calorimetry, polarizing optical microscopy and X-ray diffractometry indicate that no liquid crystalline phase but two crystalline phases are present in this material: phase I (T<66℃) and phase II (66℃<T<157℃); an isotropic state is observed at above 157℃. Combining the X-ray diffraction and the electronic diffraction, we assign the room-temperature crystalline phase I to orthorhombic sys-tem and P212121 space group with cell parameters of a = 7.43 ?, b = 6.34 ?, c = 72.07 ?, and α = β = γ = 90°. Molecular modeling reveals that the molecules in the unit cell adopt a layered structure with an antiferro-electric alignment. The structure of phase II is very similar to that of phase I. Nonlinear optical measurement shows that m-OSB is active for the second harmonic generation (SHG). Such characteri-zation of the bulk material is necessary for the understand-ing of the growth and microstructures in the films.展开更多
基金This work was supported by the Special Funds for Major State Basic Research Projects(Grant No.2002CB6 13400)the National Natural Science Foundation of China(Grant Nos.90301008and 20025413).
文摘To investigate the vacuum-deposited films of the banana-shaped mesogens, we prepared a three-ring bent-core (that is, banana-shaped) compound m-bis(4-p- octoxysryrenyl)benzene (m-OSB) and used it as a prototype for studying the related film physics. Herein the synthesis and the structural characterization of m-OSB are reported. 13C and 1H NMR spectra and IR spectrum confirm that m-OSB has a symmetric and all-trans conformation. The results of differential scanning calorimetry, polarizing optical microscopy and X-ray diffractometry indicate that no liquid crystalline phase but two crystalline phases are present in this material: phase I (T<66℃) and phase II (66℃<T<157℃); an isotropic state is observed at above 157℃. Combining the X-ray diffraction and the electronic diffraction, we assign the room-temperature crystalline phase I to orthorhombic sys-tem and P212121 space group with cell parameters of a = 7.43 ?, b = 6.34 ?, c = 72.07 ?, and α = β = γ = 90°. Molecular modeling reveals that the molecules in the unit cell adopt a layered structure with an antiferro-electric alignment. The structure of phase II is very similar to that of phase I. Nonlinear optical measurement shows that m-OSB is active for the second harmonic generation (SHG). Such characteri-zation of the bulk material is necessary for the understand-ing of the growth and microstructures in the films.
