The phase diagrams and the critical point of poly(methylmethacrylate) / methyl ethyl ketone / methanol systems were determined by measuring turbidities and viscosities, and microstructures near the phase separation regions and at the plait point were also observed by the electron microscope of the samples prepared from rapid freeze-drying.
The turbidity measurements titrating precipitant (methanol) were performed on the polymer solutions with three different molecular weights of 42000, 96000 and 416000. Thus the concentrations of the phase separations and the extent of turbidity were determined.
At the concentrations of a strongly turbid condition for each titration path, the maximum turbidity was observed near the plait point and the approximated linear behaviour of the relative intensity was shown in a log-log plot with the scaling exponent.
In the single phase region of the phase diagram at 40℃, the viscosities of dilute solutions were also determined for the polymer with molecular weight of 96000 and the maximum viscosities along the paths of fixed polymer concentrations were obtained.
For the rapid freeze-dried samples near the phase separation regions, electron micrographs show the large interspatial microstructures near critical solution but very different in regions far from plait point and it is responsible for the divergence of turbidities and viscosities.
