Polycations and Anions

Toutianoush A, Tieke B. 1998. Photoinduced switching in self assembled multilayers of azobenzene containing ionene polycations and anionic polyelectrolytes. Macromol Rapid Commun 19(11) 591 595. 

Reference has already been made to the unusual behavior, e.g., lowering of surface tension (57,58,75), development of surface viscosity (74), and so forth, observed in mixed solutions of polycations and anionic surfactants. Buckingham et al. (75) arrived at the following form of the Gibbs adsorption equation for their system (poly-L-lysine/SDS) ... 

Modification of the release rate of the loaded mesoporous silica can for instance be achieved by surface functionalization of the mesoporous silica (Song et al. 2005). This can be achieved either by applying polyelectrolyte multilayer coatings (Zhu et al. 2005), or by ionic interaction of oppositely charged polycations and anionic SBA-15 (Yang et al. 2005) or by anchoring suitable polyamines on the external surface to obtain a pH and anion-controlled nano-supramolecular gate-like ensemble (Bernardos et al. 2008). 

In 1997, Decher reported a fundamental concept regarding the multilayer nanoassemblies composed of polycations and polyanions [24]. The polymer assemblies were prepared by an alternate adsorption process, as shown in Figure 6.5. If a substrate has an anionic charge on its surface then polycation could adsorb onto the surface as a first layer. Polyanion could subsequently adsorb onto the surface by immersing in a... 

In a follow-on experiment, we formed a LbL shell on halloysite consisting of multilayers of the polycation PEI and anionic silica of 7 and 10 nm diameters (realizing by this positive/negative component alternation). Figure 14.11 shows the... 

Curiously, the effect of polyelectrolytes cm the alkali hydrolysis has not been studied until fairly recently. Polycations can bind natively charged spedes as counteranions, thus functioning as base catafysts. Morawetz and others examined tte effect of a podhvely charged pol3don, poly(l-vinyl-3-metlyliinidazolium iodide) (Mlm ) 11 on the solvol3Ttic rates of neutral and anionic esters 12,13 (22). 

Over the past 15-20 years, there has been a renewed and growing interest in the use of clay minerals as catalysts or catalyst supports. Most of this interest has focused on the pillaring of smectite clays, such as montmorillonite, with various types of cations, such as hydrated metal cations, alkylammonium cations and polycations, and polynuclear hydroxy metal cations (1-17). By changing the size of the cation used to separate the anionic sheets in the clay structure, molecular sieve-like materials can be made with pore sizes much larger than those of conventional zeolites. 

Newer 2-diethylaminoethyl ethers, such as 0-( 2-diethylaminoethyl )-agarose gels," are useful as media for electrophoresis and immunoelec-trophoresis, and the 2-diethylaminoethyl derivative of O-(2-hydroxy-propyl ) cross-linked dextran (Sephadex LH20) is an effective, lipophilic anion-exchanger. The relative stiffness of the molecular chain of 0-(2-diethylaminoethyl) dextran has been estimated from measurements of viscosity at various ionic strengths, and compared with that of other polysaccharide polycations and polyanions. 0-(2-Diethylaminoethyl) dextran itself is claimed to be toxic." ... 

Figure 2 (a) A schematk representation of a diamond-like network formed from tetrahedral tetracations and linear dianions. The volume of the polycation and the length of the dianion will play a crucial role in determining the size of the nanometersized voids present in the network, (b) A schematic representation of electrostatic enforcement of anion networks by polycations. For convenience, the concept is portrayed in two-dimensional space. The topology of each cation is defined by the spatial arrangement of the individual cationic centers... 

The main goal of this work is monitoring of the QDs optical properties during the formation of complexes with molecular templates. We have prepared CdSe/ZnS QDs with different ionic shells, which ensure cationic and anionic properties of QDs in aqueous solutions. These cationic and anionic CdSe/ZnS QDs were incubated with polyanions and polycations. 

In complex coacervation (20 pm to 1 nun), for example, aqueous solutions of active component (AC), polyanion (-) and polycation (+) are mixed. The two polymers with opposite charges (electrostatic interactions) will interact to form a deposit of coacervate at the surface of AC (i.e., acacia gum, alginate CMC with gelatine proteins and anionic polysaccharides) (De Kruif et al., 2004). Reticulation may be provoked by dilution, and modification of pH, tanperature (Figure 39.10). Gelatine and acacia gum (opposite charge at low pH) were used to encapsulate flavor lipophilic oil to be used in frozen foods and released upon heating (Yeo et aL, 2005), with liquid or solid core (Leclercq et al., 2009). 

Besides investigating nonequilibrium complexes, it is equally challenging to direct electrostatically driven complex formation into equilibrium. One vision was to obtain anisotropic complexes by mixing rod-like polycations and polyanions, such as anionic and cationic cylindrical brushes or cationic cylindrical brushes and DNA. In aqueous solution scrambled egg structures were always obtained by mixing cylindrical brush polymers with polystyrene sulfonate and with PVP side chains as well as by mixing cylindrical brushes with PVP or PLL side chains with... 

Figure 15 Conditions in bulk and surface containing a polycation (fixed concentration) and anionic surfactant. Full line is hypothetical surface tension/concentration curve of the surfactant alone dotted line is that of mixture with polycation. Simple countercations are depicted only in surface... 

Clean hair has high luster, and deposition of compounds on the hair surface usually reduces luster. This is clearly shown in Figure 37, which compares the effects of washing with various shampoos (83). Shampoo B1 contains Polyquatemium-10, a poly cationic compound known to be substantive to hair. A subsequent rinse with a shampoo containing sodium myristate produces a large decrease in luster, possibly due to complex formation between the polycation and the myristate anion. A rinse with 20% sodium lauryl sulfate, on the other hand, removes the polycation and restores the original luster of the fiber. 

If it is possible to create mesostructured phases from an anionic metal oxide/cationic surfactant system, as in the case of MCM-41, it should also be feasible using the reversed system the combination of metal oxide polycations with anionic surfactants should lead to similar materials. In both systems the ionic interactions of the metal oxide and the surfactant should be comparable and the mechanism in the reversed system should be analogous to the synthesis of MCM-41. 

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