Phase diagram, gelation temperature

Figure 4. Experimental phase diagram showing temperature versus conversion. Key o, DPEDC-NFBN (15 wt%) , DCBA-NFBN (15 wt%) a, phase separation b, gelation (x 0.6) and c, vitrification (Tg) versus x.

Here, rheology is used to characterize the gel state, whose stability, as measured thermodynamically or kinetically, can be described by temperature-concentration phase diagrams or simply time. The structural features of gelator aggregates at nanoscopic scales are described via data from the complementary techniques of electron microscopy and scattering techniques. Finally, the optical properties, including absorption and luminescence, are detailed. 

FIG. 3 Phase diagram according to the CSK. statistical-mechanical model [33] showing the sol and gel domains and the coexistence curve. 7L is the critical temperature (corresponding to the volume fraction c), Tp is the temperature at which the gelation curve meets the coexistence curve, and 7Gs.max is the limiting temperature above which there is no gelation. (From Ref. 33.)... 

Fig. 13. TXT cure diagram temperature of cure vs. the times to phase separation (doud point), gelation and vitrification for a neat and two rubber-modified systems. of the neat system is also included. The systems studied were DER331/TMAB O, gelation , vitrificaticm modified with IS parts rubber per hundred parts epoxy 1) pr eacted carboxyl-terminated butadiene-acrylonitrile (CTBN) copolymer containing 17% acrylonitrile (K-293, Spencer Kellog Co.) A, phase separation , gelation , vitrification, and 2) polytetramethylene oxide terminated with anmiatic amine (ODA2000, Polaroid Corp.) A. phase separation O, gelation O, vitrification. (DER331/TMAB/ K-293 data from Ref. )...

Figure 5.13 Predicted phase diagrams for physical gels made from low-molecular-weight molecules with junctions of unrestricted functionality 4> is the total volume fraction of polymer, and Tr is here the reduced distance from the theta temperature, Tr = — Q/T. The parameter Aq controls the equilibrium constant among aggregates of various sizes. The outer solid lines are binodals, the inner solid lines are spinodals, and the dashed lines are gelation transitions. CP is a critical solution point, CEP is a critical end point, and TCP is a tricriti-cal point. (Reprinted with permission from Tanaka and Stockmayer, Macromolecules 27 3943. Copyright 1994 American Chemical Society.)...

Fig. 8. Temperature-conversion transformation diagram lowing phase separation, gelation and vitrification for a castor oil-modiiSed epoxy system (< > , = 0.176) at different temperatures (Reprinted from Polymer International, 30, R.A. Ruseckaite, L. Hu, C.C. Riccardi, RJ.J. Williams, Castor-oil-modified epoxy resins as model systems of rubber-modified thermosets. 2 Influence of cure conditions on morphologies generated, 287-295, Copyright (1993), with kind permission from the Society of Chemical Industry, London, UK)...

Fig. 9. Temperature-conversion transformation diagram showing phase separation, gelation and vitrification for a rubber (R) and a thermoplastic (TP)-modified cyanate ester system (15 wt% of modifier) (Reprinted from Chemistry and Technology of Cyanate Ester Resins (I. Hamerton, ed.), J.P. Pascault, J. Galy, F. Mechin, 112 ISO, Copyright (1994), with kind permission from Chapman Hall, London, UK)...

Rochas and Rinaudo [569] constructed a phase diagram, where the logarithm of the total ionic concentration is plotted vs the reciprocal transition temperature (see Fig. 221). It characterizes the conformation and gelation of kappa carrageenan in KCl solutions. In domain I (relatively low concentration and high temperatureX only polymer coils are present in domain II (relatively low concentration and low temperature), the kappa carrageenan molecules are in the ordered, helical conformation, whereas in domain in (relatively high concentration and low temperature the system is in the (helical) gel state the boundary between domains II and III is not sharply known and for that reason is indicated by a wavy line. 

Phase Separation and Gelation Studies. A phase diagram of linear poly(ethylene oxide) (LPEO) and divinyl benzene (DVB) cross-linked poly(methyl methacrylate) as a function of polymerization of the latter was also researched hy duPrez and co-workers (49) (Fig. 11). The temperature of measurement was also a variable, but the curve separating the one-phased system from the two-phased system did not change much in the narrow temperature range covered. 

For charged polysaccharides, the formation of double helices and gelation depends on the ionic concentration, nature of electrolyte, and temperature. A phase diagram relating the total ionic concentration and the inverse of the temperature for conformational change (Tm has been established for each of them. For (c-carrageenan, the ionic selectivity among monovalent cations is very important (179,180) the sequence is as follows ... 

Equivalent phase diagram for a gelating system in semi-dilute solutions with a good solvent, is the monomer concentration (and each monomer is polyfunctional). is an equivalent temperature, which decreases from infinity to low values when the chemical reaction progresses. The particular model used in the text assumes instant reaction between monomers which are in contact. But the qualitative features of the diagram are more general. 

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