Carboxylic membranes polymerization

Chapiro reported that semi-permeable membranes containing carboxylic groups and pyridine groups can be obtained by polymerization of 4-vinylpyridine onto polyterefluoroethylene films previously grafted by acrylic acid. The films after grafting were neutralized by KOH in order to convert grafted polymer to poly(potassium... 

Seki and Tirrell [436] studied the pH-dependent complexation of poly(acrylic acid) derivatives with phospholipid vesicle membranes. These authors found that polyfacrylic acid), poly(methacrylic arid) and poly(ethacrylic acid) modify the properties of a phospholipid vesicle membrane. At or below a critical pH the polymers complex with the membrane, resulting in broadening of the melting transition. The value of the critical pH depends on the chemical structure and tacticity of the polymer and increases with polymer hydro-phobicity from approximately 4.6 for poly(acrylic acid) to approximately 8 for poly(ethacrylic acid). Subsequent photophysical and calorimetric experiments [437] and kinetic studies [398] support the hypothesis that these transitions are caused by pH dependent adsorption of hydrophobic polymeric carboxylic acids... 

Figure 42.2 shows a hypothetical polymeric NF membrane with carboxylic groups attached to the surface of the membrane, which is brought in contact with an aqueous solution of electrolytes. The presence of dissociated carboxylic groups on the membrane surface causes the occurrence of membrane charge. 

Ultrafiltration membranes can be very efficient at removing colloidal particles of an emulsion but normally will not stop dissolved oil from permeating. Since most membranes are polymeric, they are more stable in the presence of water, so they are best suited for aqueous systems. Since they produce only one well-clarified phase (the permeate), they should be applied to processes with stable micelles where clear continuous phase is required and where losses of continuous phase with the micellar phase can be tolerated. The use of ultrafiltration membranes in an extractive ultrafiltration process for recovery of carboxylic acids is discussed by Rodriguez et al. [/. Membrane Sci., 274(1-2), pp. 209-218 (2006)]. 

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