Measurement of cloud point temperature in polymer solutions

A temperature-controlled turbidity measurement apparatus for the characterization of polymer solutions has been instrumented and set up. The main features are the coupled temperature-light transmittance measurement and the accurate temperature control, achieved by means of peltier cells. The apparatus allows to measure cloud point temperatures by adopting different cooling protocols: low rate for quasi-equilibrium measurements and high rate for detect kinetic effects. A ternary polymeric solution was adopted as case study system showing that cooling rate affects the measured cloud point temperature.

Nucleation-controlled multiphase transitions

Thermodynamics and kinetics of phase transitions in multiphase systems have been discussed. Thermodynamically admissible transitions have been identified and transition kinetics described in terms of the extended Kolmogoroff-Avrami-Evans model. Different combinations of transitions have been described as directed graphs. Graph nodes represented individual phases, graph edges--transitions. Superposition of parallel transitions in various mother phases, simultaneous transition of the same mother phase into different target phases, and successive (chain) transitions have been analyzed. Detailed solutions for a three-phase system consisting of one liquid phase and two polymorphic solid phases have been presented.