Viscoelastic behaviors were obtained using a controlled-stress Gemini HRnano rheometer (Malvern Instruments Ltd., UK), which was able to operate at the nano-torque levels enabling to probe weak or sensitive structure. The instrument was equipped with 55 mm or 25 mm diameter stainless steel plate geometry depending on the sample viscosity, and 1 mm gap size. To prevent the slip of the sample during measurement, sand-papers were attached to the upper and lower plates of the fixture. A solvent-trap system was equipped to prevent water evaporation during measurement. The operating temperature was controlled by a peltier plate. Linear viscoelastic region, where storage (G0 ) and loss (G00) moduli are independent of the stress amplitude, was determined by performing dynamic stress sweep experiment from 0.01 to 100 Pa at a fixed frequency of 1 Hz. Dynamic frequency sweep experiment was carried out at a fixed stress within the linear viscoelastic range.