Polymerization-Induced Phase Separation. 1. Conversion−Phase Diagrams

Abstract

A thermodynamic model is given for phase separation induced by the increase of network elasticity during free-radical cross-linking polymerization. The importance of network elasticity in the field of polymer dispersed liquid crystals is stressed. The concept of a conversion-phase diagram is introduced as an attractive way to visualize the onset of phase separation in all situations where the phase separation is induced by polymerization. The results of the model are presented in conversionphase diagrams.

Model phase diagrams of binary nematic mixtures. A comparative study between linear and crosslinked polymers

“…The constant a is usually given the value 1 while the constant b is model dependent; u S is the volume fraction of the polymer when the network is formed or the volume fraction of the reference state [21][22][23] . In the numerical applications below, we adopt the values a = 1, b = 1/2 and u s = 1/2.…”

“…To our knowledge, such a comparative study has not been performed before and although it is known that both polymeric constituents lead to different phase properties, it was not known to what extent these properties are modified by the presence of crosslinks under similar conditions. Beside few exceptions 21) , experimental data are usually analyzed using the models developed for linear chains. The present study gives an indication of the conditions where the phase properties of these two systems could be considered similar and those where the architecture of the polymer matrix should be taken into account.…”

Theoretical Modeling of the Phase Separation Dynamics in Blends of Reactive Monomers

“…where i ¼ 1, 2, 3 considering all of the components are network-forming constituents, and r c,i is the segment length between cross-linked points, which may be expressed in terms of monomer conversion a as: [28] …”

“…Following the procedure of Bauer and Briber, [22] and Boots et al, [28] F 0 ¼ f 1 , f 2 , or f 3 assuming that the networks are not swollen during the progression of the cross-linking reactions.…”

Phase separation kinetics of an SA liquid crystal in a reactive epoxy-amine PDLC system: an X-ray diffraction study

“…decomposition can be found for isotropic isomolecular thermoplastic polymer blends 16) or examples of experimental studies by SAXS for reactive isotropic thermoset/ elastomer blends 17,18) . When initially miscible monomers/LC isotropic solutions polymerize isothermally, phase separation is induced by the evolution of free energy of mixing, DG m , with the extent of reaction, x. DG m depends upon enthalpic, entropic, anisotropic (nematic or smectic) and elastic energy terms after gelation [19][20][21] . The conversion at phase separation, usually named cloud point conversion x CP , depends on the dominance of each of these terms as well as on the concentration and temperature chosen 14,19) ; it also governs the subsequent development of morphology.…”