Hydrophobic polyelectrolyte systems

Many hydrolytic studies have been reported utilizing both micellar and synthetic pol3nneric systems. Cordes (7 ) and co-workers, and Ocubo and Ise ( ) have reported on systems which incorporate both the novel features of micelles and polyelectrolytes, i.e., catalyst systems which have binding sites available for both strong hydrophobic and electrostatic interaction with suitable substrates. Such hydrophobic polyelectrolyte systems have been prepared and have been termed "polysoaps" (9,10). The catalytic properties of these polysoaps has remained largely unexplored. 

Aside from their potential therapeutic applications, these hydrophobic polyelectrolyte gels have proved to be interesting in their own right. We have made a rather extensive study of their equilibrium and kinetic swelling properties in response to various chemical stimuli. We have found that their behavior cannot always be explained by theories that have been put forth for more hydrophilic systems. 

In this article we review our experience with hydrophobic polyelectrolyte gel systems. In Sect. 2 we summarize the essentials of the synthesis procedure. In Sect. 3 swelling equilibrium measurements are summarized, and in Sect. 4 these measurements are used to evaluate a simple theoretical model of gel swelling. Significant quantitative discrepancies are found, the putative sources of which are discussed. Swelling and deswelling kinetics results are discussed in Sects. 5 and 6. Section 7 summarizes the article, and suggests some implications of the reported results. 

It is of interest to consider the existence of similar effects in other polyelectrolyte systems. A polyelectrolyte for which a similar behavior may be expected is poly(vinylsulphonic) acid (HPVS). Like HPSS, it is a strong acid, but it has a less hydrophobic backbone. However, studies of the effect... 

In this chapter, approaches to estimates of (1) the polyelectrolyte (electrostatic) effect, (2) the hydrophobicity/hydrophilicity effect, and (3) the multicoordination effect, specified for metal ion/polyelectrolyte systems are described. As weak acidic polyelectrolytes, polyacrylic acid, PAA, as well as polymethacrylic acid, PMA, are exemplified as an example of weak basic polyelectrolyte, poI y(/V-vinyI i m idazoIc), PVIm, is chosen all the chemical structures of the polymer ligands are illustrated in Figure 1. Precise poten-tiometric titration studies by the use of a glass electrode as well as respective metal ion selective electrodes have been performed for the complexation equilibrium analyses. All the equilibrium constants reported in this chapter were obtained at 298 K unless otherwise stated. 

Pink MR, Greer CS, Ramesh M (1993) Hydrophobic polyelectrolyte coagulants for the control of pitch in pulp and paper systems. US Patent 5,246,547... 

We have used molecular simulation to examine configurational properties of isolated polyelectrolytes In solution. Studies on hydrophilic polyelectrolytes indicate that existing polyelectrolyte-expansion theories are inconsistent with the physical model on which they are based. Studies on hydrophobic polyelectrolytes are useful for examining the factors which Influence and induce structural transitions in these systems. 

The molecular-simulation studies discussed here consider the relatively simple case of a single polymer at infinite-dilution on an infinite lattice. Many interesting features of polymer solutions result from interchain interactions (e.g., aggregations in hydrophobic polyelectrolytes) and from interactions of polymers with interfaces (e.g., adsorption and adhesion properties). Computer simulation may also prove useful for studying such polyelectrolyte systems. 

With the advent of computers with a reasonable calculation capacity could address the application of Monte Carlo method to study of polyelectrolyte systems. The firsts article appears in the 80s [101], and the amount of papers has growing to become a voluminous literature. A comprehensive review of this literature is beyond the reach of this chapter. However, we have been greatly influenced by the work of enormous number of author, in particular a series of articles of Per Linse et al. [102]. This is possible because the species interact via several types of molecular interactions with different length and time scales. Among those involved are hydrogen bonds, electrostatic, hydrophobic. Van der Waals, hydrogen bonds interactions [103]. In order to theoretically understand the Monte Carlo... 

As has been described in Chapter 4, random copolymers of styrene (St) and 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS) form a micelle-like microphase structure in aqueous solution [29]. The intramolecular hydrophobic aggregation of the St residues occurs when the St content in the copolymer is higher than ca. 50 mol%. When a small mole fraction of the phenanthrene (Phen) residues is covalently incorporated into such an amphiphilic polyelectrolyte, the Phen residues are hydrophobically encapsulated in the aggregate of the St residues. This kind of polymer system (poly(A/St/Phen), 29) can be prepared by free radical ter-polymerization of AMPS, St, and a small mole fraction of 9-vinylphenanthrene [119]. 

In many biological systems the biological membrane is a type of surface on which hydrophilic molecules can be attached. Then a microenvironment is created in which the ionic composition can be tuned in a controlled way. Such a fluffy polymer layer is sometimes called a slimy layer. Here we report on the first attempt to generate a realistic slimy layer around the bilayer. This is done by grafting a polyelectrolyte chain on the end of a PC lipid molecule. When doing so, it was found that the density in which one can pack such a polyelectrolyte layer depends on the size of the hydrophobic anchor. For this reason, we used stearoyl Ci8 tails. The results of such a calculation are given in Figure 26. 

Responsive polyelectrolyte hydrogels that have been used for controlled release systems include gels which are hydrophobic in their neutral state... 

The design of artificial self-organizing systems is based on the ability of some molecules which contain simultaneously hydrophobic and hydrophilic groups to form molecular assemblies of definite structure in solution. Examples of the assemblies that can be used to suppress undesirable recombination processes are polyelectrolytes, micelles, microemulsions, planar lipid membranes covering an orifice in a film separating two aqueous solutions, unilamellar vesicles, multilamel-lar vesicles and colloids of various inorganic substances (see reviews [8-18] and references therein). 

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