Qicong Ying

A modified centrifugal apparatus for coexistence curve measurements―Polystyrene in methylcyclohexane

A modified centrifuge has been developed. There are four advantages to this apparatus: (i) The presence of centrifugal acceleration permits the formation of the boundary between the two phases of a fluid system more quickly after phase separation, especially for viscous fluids such as polymer blends. (ii) The rotor is able to accommodate three samples. (iii) The formation of homogeneous solutions in the one phase region can be achieved within the constant temperature rotor which can be controlled to ±0.003 °C up to ≊300 °C. (iv) The phase separation temperature can be measured as a function of centrifugal acceleration up to 1500 gravity. By using the centrifugal apparatus, the coexistence curves of polystyrene in methylcyclohexane were measured. The results in terms of critical exponents and preexponential factors were in excellent agreement with the best literature values and thus confirmed the reliability of our apparatus.

A fiber‐optic light‐scattering spectrometer for dark‐colored solutions of macromolecules

A fiber‐optic light‐scattering spectrometer with simultaneous operation at wavelengths of 488 and 790 nm is described. The spectrometer can perform both static and dynamic light‐scattering measurements, down to a scattering angle of 8°, from dark‐colored solutions of macromolecules.