Polyelectrolytes homopolymers

The Adsorption (qv) of polyelectrolytes from solution onto solid, liquid, or gas interfaces defines a vast field, one that encompasses innumerable phenomena and many technologies. To simplify, only the grossest and most common issues are introduced here (268-270). Figure 20 displays pictorially how flexible polyelectrolyte homopolymers interact with a flat, charged surface (269). The left-hand side of this cartoon indicates behavior at low Cg, a condition typically dominated... 

The microphase separation of an amphiphilic polyelectrolyte is clearly reflected in the viscosity behavior of its aqueous solution. As a representative example, Fig. 5 shows the reduced viscosities of ASt-x with different styrene (St) content plotted against the polymer concentration in salt-free aqueous solution [29], The AMPS homopolymer and its copolymers with low St content exhibit negative slopes, which is the typical behavior of polyelectrolytes in the concentration range shown in Fig. 5. With increasing St content, however, the slope systematically decreases and eventually turns to be slightly positive, while reduced viscosity itself markedly decreases. These data indicate that, with increasing St content, the... 

Polyelectrolytes are polymers having a multiplicity of ionizable groups. In solution, they dissociate into polyions (or macroions) and small ions of the opposite charge, known as counterions. The polyelectrolytes of interest in this book are those where the polyion is an anion and the counterions are cations. Some typical anionic polyelectrolytes are depicted in Figure 4.1. Of principal interest are the homopolymers of acrylic acid and its copolymers with e.g. itaconic and maleic adds. These are used in the zinc polycarboxylate cement of Smith (1968) and the glass-ionomer cement of Wilson Kent (1971). More recently, Wilson Ellis (1989) and Ellis Wilson (1990) have described cements based on polyphosphonic adds. 

The chemistry of polyelectrolyte cement liquids has been studied using NMR. Watts (1979) used this technique to distinguish between the homopolymer of acrylic acid and its copolymer with itaconic acid in various commercial polyelectrolyte dental cements. This was readily achieved because of the ability of NMR to differentiate between carbon atoms in chemical environments that are only slightly different. 

Chatterjee SK, Chhabra M, Rajabi FH, Farahani BV (1992) Thermodynamic studies of some copolymer-homopolymer-polyelectrolyte interactions. Polymer 33 3762-3766... 

We consider simple polyelectrolytes, which we define as homopolymers In which each monomer unit carries an ionizable group. Such a group may be a strong acid or base, in which case its charge is virtually independent of pH (strong poly electrolyte]. On the other hand, weak polyelectrolytes carry weakly acidic (for example carboxyl) or weakly basic (for example amino) groups their solution behaviour depends on pH. 

Scheme 14. Methods to modify p4VP homopolymers to produce cationic polyelectrolytes [160]...

Polymeric polyelectrolytes have also found applications as alternative builder ingredients [96,97], High-molecular-weight polyacrylate homopolymers and acrylic-maleic copolymers can be very effective in tying up calcium ions in the... 

This has some consequences for the behavior of these molecules, which will be discussed further on. Quite in general, the presence of charged groups causes greater heterogeneity of the polymer, and polyelectrolytes are virtually never true homopolymers. 

Cha JN et al (2003) Spontaneous formation of nanoparticle vesicles from homopolymer polyelectrolytes. J Am Chem Soc 125 8285... 

Insoluble polyelectrolyte complex may be formed when dissolved acidic and basic polyelectrolyte polymers are brought into intimate contact (131). Complex formation is generally agreed to be driven by the increase in entropy associated with the loss of small counterions into the bulk of the solution (132). Polyelectrolyte complex from concentrated solutions of strongly acidic and basic homopolymers has been shown to form sufficiently rapidly to produce a 20-30 nm thick membrane at the solution interface, as was found through reaction of dissolved poly(vinylbenzyl trimethylammonium chloride) with sodium poly (styrene sulfonate) (132). 

---