Coacervates hydration

There is evidence that random mixing of partially charge-neutralized hydrated polyelectrolyte complexes inside the coacervate phase imparts higher configurational entropy to these less stiff polyelectrolyte molecules as compared to those in the pre-coacervation phase (Kaibara et al.,... 

Processing variables, as well as polymer composition, not only will affect the mechanical properties of a coat but also may alter the hydration time of the coating. Processing variables during the microencapsulation (coacervation) process that may affect releases properties include initial pH, initial temperature, ratio of solid to encapsulating materials, and final pH.5... 

Salts and Stabilizers Effects. Electrolytes, specifically mineral salts, have a definite effect on coacervates since they carry a charge and are therefore capable of changing the charge of the coacervate. If an added salt has a greater affinity for water than the coacervate, it dehydrates the coacervate drop, and thus breaks it down and converts it to a precipitate. The more hydrated the coacervate, the harder it is for it to hold water and the less salt is required for its precipitation. 

Already Ostwald (6 ) distinguished primary hydration spheres around organic solutes and a second diffuse hydrate sphere. Bungenberg de Jong assumed coacervate formation as combination of... 

An important inherent feature of IPECs comprising branched HPEs is the intramolecular segregation of its branches a certain fraction of the branches whose charge is compensated by chains of the linear GPE is nearly completely embedded into the complex coacervate domains, whereas other branches that are virtually free of linear GPE chains form the hydrated corona. 

Coacervation and flocculation are thus very closely related phenomena and therefore it seemed natural that coacervation could in principle also be explained by an application of the " Stability Theory previously developed by them. According to this theory hydrophilic sols are characterised by two stability factors capillary electric charge and hydration. 

Examples of typical coacervation are to be found among the "linear macromolecular colloids especially among those which belong to the highly viscous type This is an indication that it will be important for the theory of a typical coacervation to associate it with the skein shape of the macromolecule. With this disappears all serviceability of the scheme of Fig. 7 for an explanation of a typical coacervation in view of the fact that it is not only incorrect as regards the symbolisation of the hydration but also as regards the conception of the colloidal particles as solid spheres. 

Only the "amorphous flocculation of corpuscular proteins could still be represented by Fig. 7 in so far as the separated highly dispersed colloid-rich phase is not microcrystalline or paracrystalline, if at any rate one replaces the very great hydration by a suitably smaller one, similarly the spheres by appropriately shaped corpuscles and thinks of these as placed in the "coacervate at short distances from each other but in such a way that there is still no question of a rigorous order... 

Further the coacervate is to be regarded as an association of macromolecules, in which the points of contact must not be thought of as static but dynamic, since it is still a typical liquid, though a viscous one. These conceptions, at which we have thus now arrived, stand diametrically opposed to the original ideas, in which it was still believed that the particles were permanently separated by a very considerable layer of hydration water. In the new ideas there is no longer any place for the view that the water present in the coacervate is bound as a whole by hydration forces. 

In the ideas concerning the internal state of the coacervate (set out in 4 p. 248) we have shown that the water (and possibly other micro-units present) must in no case be regarded in its whole as hydration (solvation) but for the greater part as occlusion liquid. 

The analytical results then show that complex coacervation may certainly not be considered as the separation of a gelatin-arabinate hydrate of constant composition (one could indeed imagine that this salt comprises such a weakly constituted lattice that it practically possesses the propertiesof a liquid). If this latter were correct the complex coacervate would have to have always the same composition (G content, A content, W content) independently of the chosen mixing proportion of the iso-hydric sols and thus must be depicted always by one and the same point in the triangle (for example point c in Fig. 18). 

Although the analytical results give therefore no support for the conception of complex coacervation as simple formation of a gelatin-arabinate hydrate of constant composition, it will nevertheless be seen from the following subsections... 

In the crystalline hydrated salt the salt ions and the water are arranged in a lattice, in the amorphous coacervates (I—III and the microionic analogue IV) there is no question of a strictly ordered arrangement over larger distances. The fact that coacervates vary continuously in composition under the influence of all sorts of variables (mixing proportion of the colloids, pH, added salts etc.) can be attributed to this. 

There is strong evidence in favour of the point of view 1. in the variants colloid anion + micro cation or colloid cation -f micro anion in the specific ion sequences for reversal of charge or for coacervation or flocculation. We remind the reader for example of the sequences Cs < Rb < K < Na < Li which occur with sulphate colloids and carboxyl colloids (p. 289). Here polarisation phenomena are still in the background and here the largest ion, that is to say, the least hydrated ion, is most suitable for reversal of charge or coacervation. This points strongly therefore to a direct contact between cation and ionised group of the colloid. 

Encapsulated flavorings currently made generally use water as a manufacturing vehicle, and thus water (hydration) is the release mechanism. However, coacervation (when cross-linked) produces an insoluble wall, and thus release is via diffusion as opposed to dissolution. In high moisture systems, this slows release but does not stop it. The extrusion process also may provide some controlled release properties in that one may use less soluble matrices thereby reducing release rates. 

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