Pa. Wells et al., PRESSURE PULSED INDUCED CRITICAL SCATTERING - SPINODAL AND BINODAL CURVES FOR THE SYSTEM POLYSTYRENE PLUS METHYLCYLCOHEXANE, Fluid phase equilibria, 83, 1993, pp. 383-390
An experimental apparatus has been constructed that enables both spino
dal and binodal points to be determined in pressure-temperature-compos
ition space. Known as the PPICS (Pressure Pulse Induced Critical Scatt
ering) unit, it enables the user to monitor the intensities of light s
cattered from polymer-solvent systems at temperatures ranging between
-20 and 150-degrees-C and pressures up to 1000 bar. The changes in the
scattered light levels are recorded as the system approaches the two
phase region. After various corrections are made, the theory of Debye-
Scholte is used to determine the location of the spinodal surface. Exp
erimental results are presented for the system polystyrene (Mw=22,000)
/methylcyclohexane at three polymer concentrations. An interesting tre
nd in both the binodal and spinodal temperatures with increasing press
ure is observed. At pressures less than 400 bar increasing pressure de
creases both the spinodal and binodal temperatures, however at pressur
es greater than 500 bar the opposite trend is observed.