| As a kind of complex fluids,lyotropic liquid crystals have good biocompatibility,non toxicity and biodegradability due to their complex rheological properties.They are widely used in cell interaction,nerve stimulation transmission,fat absorption,intelligent drug transport,pharmaceutical engineering and liquid crystal display.Nematic lyotropic liquid crystal molecules form columnar through self-assembly in water,thus forming different phase states.The phase states will change with the temperature,concentration of nematic lyotropic liquid crystal solution,the type and content of dopants,thus affecting the physical parameters such as rotational viscosity and splay elastic coefficient.In this paper,the rotational viscosity and splay elastic coefficient of nematic lyotropic liquid crystals SSY and DSCG,as well as the nematic lyotropic liquid crystals doped with salt and alkali at different temperature and solution concentration were measured by experimental method.The variation of rotational viscosity and splay elastic coefficient of nematic lyotropic liquid crystals with temperature,solution concentration,type and content of dopants was analyzed theoretically.The coupling relationship between rotational viscosity and elastic coefficient of nematic lyotropic liquid crystals and nematic lyotropic liquid crystals doped with salt and alkali was clarified,and the influence of salt and alkali doping on the coupling relationship between rotational viscosity and elastic coefficient of nematic lyotropic liquid crystals was explored.The results show that the rotational viscosity of nematic liquid crystal increases in a quadratic parabola with the increase of solution concentration,and decreases exponentially with the increase of temperature.The influence of the length-to-breadth ratios of self-assembly on the physical parameters was studied by“one-step”measurement.The splay elastic coefficient of nematic lyotropic liquid crystal decreases with the increase of temperature.At the same temperature,the higher the concentration of nematic liquid crystal solution is,the greater the splay elastic coefficient is.The doping of Mg SO4and Na Cl increases the nematic temperature range and rotational viscosity,but the doping of Na OH narrows the nematic temperature range and reduces the rotational viscosity.The doping of Mg SO4 increases the splay elastic coefficient of nematic lyotropic liquid crystal,while the doping of Na OH decreases the splay elastic coefficient of nematic lyotropic liquid crystal.The experimental results of rotational viscosity of the nematic lyotropic liquid crystals doped with Mg SO4 and Na Cl are compared with the results calculated by the viscoelastic coupling equation.It is proved that the viscoelastic coupling equation of the nematic thermotropic liquid crystals is also suitable for the nematic lyotropic liquid crystals doped with salt and alkali. |
