The liquid crystal zone for a nonionic surfactant (C12～ 14EO7) /water system was determined by using polarized light microscope. The stress sweep curves were tested (frequency= 0.0316 Hz) for several samples with RS-75 rheostress meter. The ratio of loss modulus (G") and storage modulus (G'), i.e. thδ, was quite sensitive to the change of microstructure caused by a phase transition in linear viscoelasticity range. This property could be used to define the phase transition. The results of rheology were consistent with those of 2^H NMR. The data of the macro-rheologyical measurements reflected the rules of microstructure during the phase transition. The test results could be explained by the spring and dashpot model used in liquid crystal structure.

Key words: NON IONIC SURFACTANTS, LIQUID CRYSTAL, PHASE DIAGRAM, VISCOELASTICITY, POLYETHENOXY ETHER, POLARIZING MICROSCOPES