Coacervates functionality

Figure 8.5 illustrates the sort of separation this approach predicts. Curve A in Fig. 8.5 shows the weight fraction of various n-mers plotted as a function of n. Comparison with Fig. 6.7 shows that the distribution is typical of those obtained in random polymerization. Curve B shows the distribution of molecular weights in the more dilute phase-the coacervate extract-calculated for the volumes of the two phases in the proportion 100 1. The distribution in the concentrated phase is shown as curve C it is given by the difference between curves A and B. 

Today, Oparin s coacervates are not as favoured as Fox s microspheres or Wachtershausers s vesicles, and RNA replicators are preferred to Haldane s viroids, but these differences have not changed the substance of the original opposition. Between the two fundamental functions of life - metabolism and replication - Oparin gave an evolutionary priority to metabolism, while Haldane gave it to replication, and the choice between these two alternatives is still the key point that divides the origin-of-life theories in two contrasting camps. 

Figure 2. Formation of coacervates at various pH values as a function of the ratio of protein and carbohydrate solutions (1)...

The viscosity is influenced by the pH of the medium and the concentration and relative amounts of the initial solutions from which the coacervate is formed. The relationship between these factors is illustrated in Figure 3. The formation of coacervates is shown as a function of viscosity and concentrations of gelatin and gum arabic solutions at various pH values. 

A very frequently described family of polymers subjected to simple coacervation are cellulose derivatives, particularly ethyl cellulose (EC). ° While most cellulose ethers are soluble in water, EC and the cellulose esters are insoluble or only partly soluble in water, e.g., as a function of pH. For coacervation of EC, toluene is a preferred good solvent and cyclohexane a poor solvent. Gradual addition of cyclohexane to a solution of EC desolvates the polymer. Alternatively, EC can be dissolved in hot cyclohexane cooling to room temperature induces polymer phase separation. In both these cases, the coacervate film or droplets can be hardened by exposing the coacervate to a large volume of cyclohexane, whereby physical cross-links are formed. 

In coacervation by Polymer 2-Polymer 3 repulsion, the addition of Polymer 3 causes phase separation between the two polymer species dissolved in a common solvent 1. This phase separation produces a viscous, liquid phase of Polymer 2, i.e., the coacervate, and a low-viscous phase of Polymer 3, often called continuous or polymer-poor phase. Under stirring, coacervate droplets are formed and dispersed in the continuous phase. The solubility of Polymer 3 in solvent 1 should be superior to that of Polymer 2 in this common solvent. For particle production, the Polymer 3 should also function as stabilizer for the coacervate droplets to prevent their aggregation. Further, for the entrapment of a biologically active material, the coacervate must have a certain degree of fluidity and a high affinity to the core material, whereas the affinity between core material and continuous phase should be low... 

The critical concentration of FBLG in dioxan has been measured as a function of the number of residues 28). However, since no replication and mutation processes are involved in coacervation, it seems more natural to seek the origin of life in the DNA structures and the RNA activities. 

Formation and Structure of Middle Phase Microemulsion. The 1 - m - u transitions of the microemulsion phase as a function of various parameters are shown in Figure 4. Chan and Shah (31) compared the phenomenon of the formation of middle phase microemulsion with that of the coacervation of micelles from the aqueous phase. They concluded that the repulsive forces between the micelles decreases due to the neutralization of surface charge of micelles by counterions. The reduction in repulsive forces enhances the aggregation of micelles as the attractive forces between the micelles become predominant. This theory was verified by measuring the surface charge density of the equilibrated oil droplets in the middle phase (9). 

All of the above quantities were plotted as a function of system pH for each complex coacervation system studied. Only a few of the many plots obtained are included in this paper. An effort was made to present results in terms of 0. In addition, several plots... 

Since the first commercial application to carbonless copy paper in the 1950s, microencapsulation with coacervation technology has been successfully applied to many other areas, such as food, pharmaceuticals, cosmetics, biotechnology, and agrochemicals. The capsules provide such functions as controlled release, taste masking, improved heat and oxidative stability, reduced volatility/ flammability/toxicity, separation of reactive incompatibles, improved shelf-life, conversion of liquids to solids, and improved flowability as well as material handling. Among various coacervation processes, complex coacervation is most prevalent. 

Proteins are a class of biomaterials, more used in bioencapsulation, in association with their functional and nutritional properties. Proteins may act not only as matrices but also as emulsifiers, favoring the simple or complex coacervation as bioencapsulation technique. 

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