Solvent-induced phase separation SIPS

The phase-separation method was developed at Kent State University in the late 1980s. It consists of in sitn segregation of liqnid crystalline microdroplets from a homogeneous mixture of liquid crystal and polymer/prepolymer, indnced by a factor that gave the techniqne its name, as follows (a) polymerization-induced phase separation (PIPS) (b) solvent-induced phase separation (SIPS) and (c) thermally induced phase separation (TIPS). 

Liquid crystal and polymer dispersions are fabricated using thermally-induced phase separation (TIPS), solvent-induced phase separation (SIPS), or Polymerization-induced phase separation (PIPSX/I)- For TIPS, a homogeneous mixture of a low-molecular weight liquid crystal and thermoplastic polymer is cooled below the critical phase separation temperature to induce phase separation into liquid crystal rich and polymer rich domains. The morphological properties (domain size, number of domains per unit volume, and the composition of the domains) depend primarily on the choice of liquid crystal and thermoplastic polymer, the initial weight fraction of liquid crystal in die initial mixture, and the rate of cooling. 

Among these various phase separation techniques, pressure-induced phase separation is particularly important since pressure changes can be brought about uniformly and very fast throughout the bulk of a solution. This would not be so in other techniques due to for example heat (in TIPS) and mass transfer (in SIPS) limitations. The technique therefore opens up new opportunities for formation of microstructured materials with potentially more uniform morphologies. It is also important to recognize temperature, solvent, reaction, or field-induced phase separation may all be carried out at elevated pressures if so desired, as such all modes of phase separation methods are of interest when working with near-critical or supercritical fluid systems. 

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