Gel phase diagrams

The formed gels showed thermally reversible sol-to-gel transition due to the non-covalent interactions. The sol-to-gel phase diagram for C4mim/BF4 and C4py/BF4... 

Fig. 2.19 Sol-to-gel phase diagram the minimum gel concentration of 69 V5. temperature in tetrachloromethane ( ), in ethyl acetate (0) and in cyclohexane (A).

Fig. 1 The sol-gel phase diagram of compound 12 relationship between the minimum gelation concentration and temperature.

Taking into account the usual conditions of the hydrogel application, we shall limit our discussion to that part of the phase diagram which depicts the swollen gel and touch upon the collapse only in passing since a detailed analysis of this phenomenon is given by Tanaka [96, 97], Ilavsky [19, 98], and Khokhlov [99],... 

It was possible (16) to obtain gels from the crude pectins in presence of sucrose and at acidic pH. The phase diagrams of the pectin systems (Figure 4) have been first established. The gel state was simply observed by visual inspection of the products obtained after heating (100°C, 30 min) and cooling (to room temperature) solutions containing different quantities of pectins and sucrose at pH3 (citric acid). 

FIG. 4 Phase diagram of fully hydrated DPPC bilayers. Different phases found are also schematically shown Lp, gel P, rippled gel L I, interdigitated gel and L , liquid crystalline phases. (From Ref. 50. Copyright 1999 The Japan Society of High Pressure Science and Technology.)... 

The information available on aqueous polymer blends is qualitative in nature because of the lack of a suitable theory to interpret the experimental observations. Mixed gels can be comprised of an interpenetrating network, a coupled network (as discussed above), or a phase-separated network [2]. The latter is the most common as the blends have a tendency to form two phases during gelation. In such cases the miscibility and thermodynamic stability have to be empirically investigated and proper conditions for miscible blends identified. This involves a phase diagram study as is described in [3]. 

Figure 8. Binary phase diagram of Cj GE -water system. G gel phase, N neat phase, I isotropic solution, II two liquid phase...

Fig. 15.4 Schematic ternary-phase diagram of an oU-water-surfactant microemulsion system consisting of various associated microstructures. A, normal miceUes or O/W microemulsions B, reverse micelles or W/O microemulsions C, concentrated microemulsion domain D, liquid-crystal or gel phase. Shaded areas represent multiphase regions.

Figure 3.5. Phase diagrams obtained for two monodisperse water-in-oil emulsions stabi-hzed with SMO. (O) totally dispersed (O) flocculated (fluid-sohd) ( ) totally flocculated (gel). (Adapted from [11].)...

Evidence for the formation of gels from aPS systems is obtained from simple mechanical, (1.4.5) viscoelastic, (7.8) thermodynamic (1.6) and spectroscopic ( ) techniques. Simple tube tilting, falling ball methods and differential scanning calorimetry have been used to determine the phase diagrams for a number of systems. Viscoelastic measurements on the aPS-carbon disulfide system show that the low frequency response indicative of a... 

Gels are obtained for concentrations shown in the temperature-concentration phase diagram (Figure 1). Electron spin resonance (ESR) shows (10) that for a given temperature only a fraction (p) of the initial steroid concentration is transferred from the solution to the gel network. The picture of this gel is thus of a supersaturation gel there is a dynamic equilibrium between free molecules in solution and aggregated steroid molecules included in the long objects which constitute the gel network. The free steroid molecules concentration at a temperature where the gel state is stable is (1-p), while C p is the steroid concentration within the solid-iike gel aggregates. 

We can apply classical germination laws to this supersaturated system thus, the Avrami-Mempel laws confirm the unidimensional growth of the solid-like gel network. Induction times can also be studied in this framework 11). Here, we are interested first by the different kinetic behaviors which are dependent upon the location in the phase diagram of the initial solution defined by its supersaturation degree. 

The gel region of the phase diagram in Figure 1 is divided in two zones ... 

Note A ringing gel is often a hydrogel with a surfactant as a third component and has a composition within an isotropic, one-phase region of its ternary phase diagram... 

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