Chain dimensions Polyacrylics

The present review deals mainly with two examples of polyelectrolyte phase behavior as discussed above. As an example for an H-type precipitation, the solution properties of polyvinylpyridinium chains are monitored as function of added inert salt. Here, we focus on the determination of the effective charge density and of the solvent quality parameter which are supposed to play a central role for the understanding of polyelectrolyte solution without specific counterion interactions. The second system under investigation comprises the interaction of polyacrylic acid with alkaline earth cations which exhibit very specific interactions, thus representing an example for type L-precipitation. Here the coil dimensions close to the phase boundary are compared to those close to type H-precipitation with inert added salt. 

As early as 1951, Flory and Osterheld [18] could show that partially ionized polyacrylic acid in aqueous solution of an inert salt shrinks in size if the concentration of the inert salt is increased. This shrinking process can be pushed towards the unperturbed dimensions of the NaPA chains. Known from neutral polymers as 0-state, it is reached for fully ionized NaPA [50] at T=15 °C and 1.5 M KBr. In several papers, the dependence of the intrinsic viscosity was investigated as a function of the molar mass [51]. Data were... 

The unperturbed average dimensions of polyacrylate chains would thus be only slightly dependent upon ionic strength, the characteristic ratio, value at 15° ranging from about 11 to 13 going from... 

Drag reduction is shown by polysaccharides, which are linear in nature. Highly branched materials such as gum arabic and dextran do not seem to reduce drag (17). Polyelectrolytes, such as partially hydrolyzed polyacrylamide (64,106), polyacrylic acid (118), acrylamide sodium acrylate copolymer (119), and sodium alginate (120), show higher drag reduction when the chain is extended or there is increment in coil dimensions. The coil expansion takes place because of coulom-bian repulsion and solvent steric hindrance of side group and main chain (119). 

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