Investigation of the General Properties of Some Polyelectrolyte Complexes PDF Download

Author: Nermin Acar
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Languages : en
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Book Description
Polyelectrolyte complexes, also called interpolymer complexes, are new class of chemically distinct and identifiable compounds. They are formed by polyelectrolytes that are macromolecules carrying a relatively large number of functional groups, orunder suitable conditions can become charged. Polyelectrolytes interact with various low and high molecular weight substances and form interpolymer complexes. These complexes are either separated from the solution as solids (polycomplex salt) or may settle as a polyelectrolyte complex gel, and they can be soluble in solution by controlling experimental factors. They are, in general, obtained in either case, by mixing polyelectrolytes solution, and by matrix polymerization. Significant differences might exist between the chemical, thermal and mechanical properties ofinterpolymer complexes with respect to their components and experimental conditions. All biological macromolecules, proteins, nucleic acids, and polysaccharides are polyelectrolytes and interact with each other and small ions during their biological function. Their electrostatic interactions contribute a significant part of the structural stabilization of biological molecules and they are major determinants for the kinetics of biological process. Considering all these vital processes research on the polyelectrolyte complexes obtained by synthetic polyelectrolytes might be a simple model system for the complicated biopolymer reactions. Studying the special properties of polycomplex formation between synthetic polyelectrolytes and low molecular weight compounds can be useful for understanding the nature of protein-lipid interaction in biomembranes or in the mechanism of protein denaturation. On the other hand, polyelectrolyte complexes are very promising materials for semi-permeable membranes for the industrial applications such as desalting of sea water, ultrafiltration and purification of aqueous solution and also for ultrafiltration of biological liquids.With all the above given respects, numerous studies have been made successively onvarious polyelectrolyte complexes in the last two decades. However very few studies have been reported on the interaction between some certain polyphosphates andvinylpyridine polymers. One of a few studies with poly(phosphate) has been given by N.Acar and T.Tulun on the interaction of poly(sodiumphosphate) (PSP) andpoly(4-vinylpyridiniumchloride) (P4VPHCl). The present study was aimed to investigate the interaction between poly(sodiumphosphate) and poly(4-vinylpyridiniumchloride) with 4-amino benzoic acid (low molecular weight compound) individually as well as the detailed continuation of the previous work which dealt with the polyelectrolyte complex formed by PSP and P4VPHCl.Poly(sodium phosphate) is interesting because it is an inorganic polymer and, rather unusually it is one of the few anionic polymers of the integral type. Actually polyphosphates are somewhat analogous to the nucleic acids. Vinylpyridine polymers have particular importance as polyelectrolytes and have great ability to develop interpolymer complexes with polyacids.The present study aims to form polyelectrolyte model complexes similar to or mimicking biologically active compounds and, thus, to understand the operating mechanism of biopolymers in living organisms through the investigation of the structure and various features of these model complexes. In the experimental part of the study, insoluble polyelectrolyte complexes were obtained from the both, concentrated and dilute solutions of PSP and P4VPHCl. Stoichiometry of the isolated complexes were found to be 1:1 as a result of analysis of the supernatant liquid in conjunction with concentration of the initial components.In the dilute aqueous solution, occurrence of polyelectrolyte complex was proved by UV spectroscopy. Salt effect of NaCl, the effect of NaCl on complex formation andthermal properties of complexes were investigated.Regarding the reaction of PSP with 4-amino benzoic acid, hydrochloride (PABCl),the stoichiometry of complex was found as 1:1.2 using viscometric and volumetricanalysis of the supernatant. Besides, spectroscopic and conductometric methods were used for the complex stoichiometry. The experimental factors such as pH,ionic strength and temperature that affect the stoichiometry of complex were investigated.In the case of the poly(4-vinylpyridine) (P4VP) with 4-aminobenzoic acid, IR spectroscopy , potentiometry and DSC were used and the nature of binding between the components was identified as hydrogen bonding.It is known that transition metals take part in the biochemical process. In the present study, interaction of copper (II) with P4VP- PABA complex system is of interest. Potentiometric method was used to follow the above stated interaction in aqueousethanol solution for P4VP-PABA system. Protonation and the stability constants ofP4VP-PABA system were determined.Swelling properties of polyelectrolyte systems have been studied largely due to their industrial uses. In order to investigate the swelling properties of P4VPHCl-PSP system, PSP and P4VP that is the initial component of polycation were subjected to irradiation for six different radiation doses to obtain cross linked structure. It is found that radiation has no affect on PSP.After irradiation the insoluble, the gel, parts were determined by soxhlet extraction and UV spectroscopy. Up to certain dose the gelpercent of P4VP samples increased, and thereafter remained unchanged. From the relation between gel fraction and radiation dose, the efficiency of crosslinking and of scission were determined. Irradiated P4VP that contained only gel part was quaternized to obtain waterswellable P4VPHCl gel. The interaction of P4VPHCl gel with the aqueous solution of PSP was investigated considering ionic strength and pH.