POLYMER SOLUBILITY AND SOLUTIONS

Most people associate polymers with solid materials—from rubber bands to car tires to Tupperware — but what about acrylic and latex paints or ketchup and salad dressing or oil-drilling fluids The thermodynamics and statistics of polymer solutions is an interesting and important branch of physical chemistry, and is the subject of many good books and large sections of books in itself. It is far beyond the scope of this chapter to attempt to cover the subject in detail. Instead, we will concentrate on topics of practical interest and try to indicate, at least qualitatively, their fundamental bases. Three factors are of general interest  

What solvents will dissolve what polymers  

How do the interactions between polymer and solvent influence the properties of the solution  

To what applications do the interesting properties of polymer solutions lead  

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In this chapto, we have illustrated the effects of molecular architecture of polysulfobetaines on solution behavior under specilBc environmental conditions of pH, added electrolytes, and polymer concentration. The nature of the comonomer and amount of incorporation of the sulfobetaine within the polymer chain dictate the polymer solubility and solution behavior. Polyampholyte behavior is realized for acrylamide-based systems containing the sulfobetaine moiety. Polyelectrolyte behavior is coupled with polyampholyte behavior for cyclopolymers containing >40mol% sulfobetaine. Incorporation of the sulfobetaine monomer hinders hydrophobic association for the pH responsive copolymers of series TV at low degrees of ionization. 

Solubility and Solution Properties. Poly(vinyhdene chloride), like many high melting polymers, does not dissolve in most common solvents at ambient temperatures. Copolymers, particularly those of low crystallinity, are much more soluble. However, one of the outstanding characteristics of vinyUdene chloride polymers is resistance to a wide range of solvents and chemical reagents. The insolubiUty of PVDC results less from its... 

Buccal dosage forms can be of the reservoir or the matrix type. Formulations of the reservoir type are surrounded by a polymeric membrane, which controls the release rate. Reservoir systems present a constant release profile provided (1) that the polymeric membrane is rate limiting, and (2) that an excess amoimt of drug is present in the reservoir. Condition (1) may be achieved with a thicker membrane (i.e., rate controlling) and lower diffusivity in which case the rate of drug release is directly proportional to the polymer solubility and membrane diffusivity, and inversely proportional to membrane thickness. Condition (2) may be achieved, if the intrinsic thermodynamic activity of the drug is very low and the device has a thick hydrodynamic diffusion layer. In this case the release rate of the drug is directly proportional to solution solubility and solution diffusivity, and inversely proportional to the thickness of the hydrodynamic diffusion layer. 

The suggested rod like structure of the pendant-type FVP-Co(III) complex is supported by the viscosity behavior of the polymer-complex solution (Fig. 3)2 The PVP-Co(III) complexes have higher viscosity than PVP this suggests that the polymer complex has a linear structure and that intra-polymer chelation does not occur. The dependence of the reduced viscosity on dilution and the effect of ionic strength further show that Co(en)2(PVP)Cl] Cl2 is a poly(electrolyte). The polymer complexes with higher x values have a rodlike structure due to electrostatic repulsion or the steric bulkiness of the Co(III) chelate. On the other hand, the solubility and solution behavior of the polymer complex with a lower x value is similar to that of the polymer ligand itself. 

This means that Increased surfactant content was always accompanied by a minimum Increase of water content according to Equation 3. Plotting the solubility of the polymer In the pentanol/styrene solution when pentanol Is gradually replaced by the surfactant/water combination according to Equation 3 shows the reflection between polymer solubility and the amount of surfactant/water aggregate present (21). In fact, a linear reduction of polymer solubility was found with Increase surfactant/water content. Figure 5. A surfactant concentration of 9.5% accompanied by water to 2.46% would result In zero solubility of the polystyrene. This means that a composition of pentanol/styrene 25/75 dissolves 42% polystyrene but that the polystyrene Is completely Insoluble In a composition 75% styrene, 13% pentanol, 9.5% surfactant and 2.5% water. Or, expressed In a different manner 1 molecule of polymer Is removed for 1.3 molecules of surfactant and 3.3 molecules of water added. 

The nature of hydrophobic interactions and their effects on the structure and properties of water have been extensively studied, particularly for small molecules (i 3). In contrast, the introduction of hydrophobic associations into synthetic water-soluble polymers to control solution rheology has received rather limited and recent study (4-7). To better understand the relationships between polymer structure and solution properties, we have synthesized and characterized a series of copolymers of acrylamide and N-substituted alkylacrylamides and terpolymers containing anionically charged carboxyl groups. Solution properties of these systems have been obtained in both the dilute and semidilute concentration regime, to probe the influence of intra- and intermolecular interactions. In addition, the influence of the shear field and solvent quality on the associations was studied. 

TSY Tsypina, N.A., Kizhnyaev, V.N., and Adamova, L.V., Triazole-containing polymers Solubility and thermodynamic behavior in solutions (Russ.), Vysokomol. Soedin., Ser. A, 45, 1718, 2003. 

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