Scrambled-egg model

Figure 9.9. Polycomplex formation from two high molecular weight polymers. Scrambled eggs model.

The ladderlike structure, where complex formation takes place on a molecular level via conformational adaptation The scrambled egg model, where a high number of chains are incorporated into a particle... 

FIGURE 56.3 PEC models (a) ladder model and (b) scrambled egg model. (With kind permission from Springer Science+Business Media Polyelectrolytes in Polyelectrolytes and Nanoparticles, 2007, pp. 5-45, Koetz, J., Kosmella, S., Howard, G., Barth, D., and Harald, P., Springer, Berlin, Germany.)... 

Scheme 5 Representation of ladder and scrambled egg structures. Black lines represent large polyions (negative), while gray lines with squares represent poly ions of opposite charge (positive), (a) Ladder representation, where insuffieient ion pairing occurs under certain stoichiometric conditions leading to macromolecular aggregates, insoluble, and soluble PECs, (b) Scrambled egg model, where polymers of comparable size complex to yield insoluble PECs under certain conditions. Reprinted with permission from [65]. Copyright 2007 Springer...

FIG. 2 Structure models ladder and scrambled egg structure. (From Ref. 23.)... 

Two structural models are discussed in the literature for polyelectrolyte complex (PEC) formation, depending on the components (weak or strong polyelectrolyte, stoichiometry, molecular weight) and the external conditions (presence of salts, etc.) ladder-like (complex formation takes place on a molecular level via conformational adaptation) or scrambled egg structure (large number of chains in a particle) (Scheme 5) [65]. 

The determination of the tertiary structure of the hens egg white lysozyme, and the subsequent proposal that the side-chain carboxyhc acid group of Glu 35 act as a general acid, and the ionised side chain of Asp 52 acted to electrostatically stabilise an oxocarbonium ion intermediate, led to a search for a manifestation of these phenomena in model systems [6]. In the scramble electrostatic stabilisation was invoked where there was no compelling reason to distinguish it from ordinary nucleophilic participation. Thus, 3,5-dichlorophenolate departs from compound XXXII 100 times faster than from its p-isomer [94] a similar 22-fold acceleration of the ortho compared to the para isomer was observed with compound XXXIII. The rate acceleration in both cases was attributed to electrostatic stabihsation, but since the 3-methoxyphthalide was in both cases the product, it is not clear why humdrum neighbouring group participation was not invoked. 

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