In this study,a novel series of chiral 1,2-propanediol derivatives with different electron-donating and electron-withdrawing groups were synthesized and characterized by FT-IR and ~1H NMR.The helical twisting properties of all the chiral dopants were investigated by doping the chiral dopants into a nematic liquid crystal host（SLC-1717）.The results indicate that the donor-acceptor electron effect have a prominent influence on helical twisting property of the chiral nematic phase induced by the chiral dopants. Introducing electron-withdrawing groups into the terminal ends of chiral 1,2-propanediol can decrease the absolute values of the helical twisting power.In addition,the helix inversion temperatures of the induced chiral nematic phase are variational with the change of terminal groups.
Based on an analysis of the 1H NMR,FT-IR,UV-vis spectra,a chiral trimeric phenylene vinylene derivative（ChTPV） synthesized by a Wittig reaction was determined to have a trans-cis configuration, and it could be isomerized to the trans-trans isomer when treated with iodine.The melting point of ChTPV with a trans-trans configuration increased by 162.1℃compared to the trans-cis isomer,and the ChTPV with trans-trans configuration exhibited the typical liquid-crystalline texture of the smectic A in the heating process.The results indicated that the molecular configuration can influence the formation of the liquid crystalline phase of ChTPV.
This paper deals with the relationships between the structure of poly（p-phenylene vinylene）（PPV） film and treatment temperature and their mechanical properties.The chemical structures and aggregated structures of PPV precursor（PPVpre） and PPV treated at three node temperatures（125,155 and 230 ℃） were investigated by FTIR spectrometry and X-ray diffraction.The results show that the content of trans-conformation and the size of the crystalline domains increased with the increase of treatment temperature.The mechanical performances of the corresponding polymers were studied by nanoindentation.The elastic modulus and hardness of PPV films decreased with the increases of the content of trans-conformation and the size of the crystalline domains.These results suggest that the conformation and the size of the crystalline domains are able to induce the elastic modulus and hardness variation of PPV films.
