Anionic polymers polyanions

The polymers used in DDSs may be classified using different criteria. According to the charge they bear, they may be divided into neutral polymers, anionic polymers (polyanions) and cationic polymers (polycations). This chapter is devoted to the DDSs containing cationic polymers of pharmaceutical interest. 

Since multiple electrical and optical functionality must be combined in the fabrication of an OLED, many workers have turned to the techniques of molecular self-assembly in order to optimize the microstructure of the materials used. In turn, such approaches necessitate the incorporation of additional chemical functionality into the molecules. For example, the successive dipping of a substrate into solutions of polyanion and polycation leads to the deposition of poly-ionic bilayers [59, 60]. Since the precursor form of PPV is cationic, this is a very appealing way to tailor its properties. Anionic polymers that have been studied include sulfonatcd polystyrene [59] and sulfonatcd polyanilinc 159, 60]. Thermal conversion of the precursor PPV then results in an electroluminescent blended polymer film. 

Structural units of binary polycompounds with main group elements consist of one-, two- and three-dimensional polymers, as well as cage-like polycyclic anions. These polyanions can be converted into molecular compounds by appropriate chemical reactions. 

The toxicity of polycarboxylic acid polymers is more sensitive to polymer structure and molecular weight than antitumor activity. The acute toxicity is markedly decreased with decreasing molecular weight (Table VI and XI). Further,polyanion polymers have been shown to highly sensitize mice to bacterial endotoxin (39)> this activity is strikingly molecular weight dependent as shown in Tables VII and XI as well as dose dependent ( 3. The enhanced sensitivity to endotoxin by synthetic anionic polymers has been extensively studied, but the mechanism of action is still not understood (39)-... 

These data point to basic differences between the cellular response and pharmacologic efficacy between the structurally modified anionic polymers and pyran. These data give precedence for the synthesis and evaluation of other polyanionic polymers. 

Kanekiyo explored linear polymer imprinting (1-D), the formation of a 1 1 dimer between anionic polymers and cationic polymers was utilised. The polyanion fragment contains boronic acid units to complex with AMP (Scheme 49). On removal of AMP from the precipitated polyion complex a cleft that has the memory for the AMP template is created." It was demonstrated that this cleft shows high affinity with AMP and the precipitate (gel) displays reversible swelling-shrinking in response to the binding of AMP. When this gel is deposited on a QCM resonator, it responds to small changes in the concentration of AMP." ... 

CMC hydrates rapidly and forms clear solutions. Viscosity buUding is the single most important property of CMC. DUute solutions of CMC exhibit stable viscosity because each polymer chain is hydrated, extended, and independent. The sodium carboxylate groups are highly hydrated, and the ceUulose molecule itself is hydrated. The ceUulose molecule is linear, and conversion of it into a polyanion (polycarboxylate) tends to keep it in an extended form by reason of coulombic repulsion. This same coulombic repulsion between the carboxylate anions prevents aggregation of the polymer chains. Solutions of CMC are either pseudoplastic or thixotropic, depending on the type. 

Ladenheim and Morawetz [23] also showed that the reactivity of the carboxylate units in partially ionized poly(methacrylic acid) (PMA) toward BrCH2COO in the bromine displacement reaction was greatly diminished, while the reaction proceeded at an appreciable rate with uncharged p-bromoacetamide [23]. This inhibition of the reaction of the polyanion with a small anionic reagent can be attributed to the electrostatic repulsion between the polymer and the reagent. 

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... 

The poor response of the synthetic polymers in the cytotoxicity tests with insulinoma cells (Table 4) provides further support for the utilization of polyanions as the inner cell suspending fluids. Given the rigid nature of the moderate molecular weight anionic polysaccharides, it seems reasonable that low molecular weight polycations can be effective in membrane formation, due to their high diffusivity. This will be elaborated upon in the discussion. 

The deliberate introduction of multifunctional branching into anionically prepared polydiene and poly (diene-co-styrene) polymers produces materials with unique morphological and viscoelastic properties (1-3). Work has included synthesis of symmetric star polymers produced by reaction of living polyanionic "arms" with multi-functional chlorosilane (4-9),... 

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