Poliakrilik asit ve akrilidon anyonik polimerler-metal komplekslerinin spektrofotometrik yöntemle incelenmesi

Abstract

Poliakrilik asit (PAA) heterojen polimerizasyon yöntemi ile toluende dibenzoil peroksit başlatıcısı kullanılarak sentezlenmiştir. Sentezlenen PAA 'in molekül ağırlığı Mark-Houwink eşitliği ile belirlenmiştir. Son zamanlarda geçiş metal iyonlarının sentetik polimerlerle kompleks bileşimleri üzerinde yoğun çalışmalar yapılması sebebiyle bir polielektrolit olan PAA, akrilidon anyonik polimeri (AAP) ve polivinil pirolidonun (PVP K-30) metallerle ve proteinle kompleksleri farklı pH, konsantrasyon için incelenmiştir. PAA-Metal komplekslerinin n^/ncu molar oranlarının 2, 5, 8, 15 olacak şekilde oluşan kompleksleri ilk olarak UV-visible spektrofotometresinde incelenmiştir. Kompleks oluşumunda -COOH grubunun etkisini görebilmek için akrilik asit ve vinilpirolidon monomerinden oluşan ve akrilidon anyonik polimer olarak adlandırılan ticari kopolimerin VP:AA oranmm 25:75 (KOP75) (MA=250.000 gr/mol) 50:50 (KOP50) (MA=80.000 gr/mol), 75:25 (KOP25) (MA =250.000 gr/mol) ve PVP (K-30) polimerlerinin metal kompleksleri de benzer şekilde UV-visible spektrofotometrisinde incelenmiştir. İkili (polimer-metal, polimer- protein) ve üçlü (polimer-metal-protein) kompleksleri ayrıca FT-IR spektrofotomet- resi ile de incelenmiştir. Komplekse girme eğiliminin pH 3'te daha zayıf olduğu, -COOH grubu fazlalaştıkça kompleksleşmenin arttığı gözlenmiştir. PVP 'un kompleks yapma özelliğinin diğerlerine göre hemen hemen olmadığı ve FT-IR spektrofotometresinin kompleks oluşumunu incelemeye uygun bir yöntem olduğu belirlenmiştir. Ayrıca PAA-Cu(II) kompleksinin oluşumunun varlığı kondüktometrik ölçümlerle gösterilmiştir. Ancak titrasyon sırasında Cu2+ ve Na+ iyonların yer değiştirmesi söz konusu olduğundan mekanizma hakkında ayrıntılı açıklama yapabilmek güçtür.

In recent years, already several systems have been described in which binding of metal ions a polymer is of a cooperative character. It was shown that such binding must lead to an irregular distribution of the metal between the macromolecules. It is well known that intermacromolecular complexes play an important role in many biological functions. An investigation of mechanism and the factors affecting complexation using well-characterized synthetic polymer is of importance as these systems serve as models for complex biopolymer. A systematic study has also been recently carried out on the formation of water soluble and insoluble ternary complexes of proteins with synthetic polyelectrolytes is shown that when protein and polyelectrolyte are incapable of binding to one another metal ions can promote the formation of a stable ternary complex. These complexes revel high immogenecity and confer high levels of immunological protection. The physico-chemical properties of these systems have not yet been investigated and therefore, the mechanism of the formation of ternary polyelectrolyte-metal-protein complexes and their remain open. First, Polyacrylic acid (PAA)-Cu(II), Acrylidone Anionic Polymers (AAP)- Cu(II) and Polyvinylpyrrolidone (PVP-K-30)-Cu(H) complexes in aqueous solution were investigated comparatively with UV-visible, FT-IR spectrophotometric, and conductometric titration methods. The complex species in aqueous solution have been determined by spectrophotometry depending on the pH value and PAA, Cu(II) concentrations. Complex formation of PAA, AAP with bovine serum albumin (BSA) was also studied. The contact between proteins with PAA and AAP are achieved via chelate unit formation in which the copper ions are located at the center. Material and Methods PAA, was obtained by radical polymerization of vacuum distilled acrylic acid by using dibenzoyl peroxide as initiator, the distribution of these configurations -the tacticity- depends on the monomer, the temperature of polymerization and the solvent. vui Solubility, when poly (acrylic acid) is dried under conditions which is mild enough to prevent crosslinking these polymers are extremely soluble in water. PAA is soluble in water, dioxane, dimethlyformamide, ethanol, methanol, 2- propanol at 25 °C and insoluble in acetone, propylene carbonate, ethylene carbonate, ethyl ether, benzene and cyclohexane. In this study, molecular weight of polymer was found to be about 90,000 by using following equation. [ r, ] = 8,5 104 Mv05 AAP have been used in these studies were obtained from International Specialty Product (ISP). As Anionic Acrylidone Polymers, COP75 (VP:AA, 25:75), COP25 (75:25) and COP50 (VP:AA, 50:50) were used. AAP, dissolve readily when added to aqueous alkaline solutions maintained at pH 4,5 or higher. The unneutralized polymers are insoluble in water and many organic solvents, but soluble in blends of waters and water-misuble solvents e.g., ethanol, isopropanol (IP A), acetone, tetrahydrofuran, ethylene gylcol and methyl cellosolve. Acrylidone anionic polymers, linear, random copolymers of vinylpyrrolidone and acrylic acid. Sample Structure £=° CH - CH, CH - CH, COOH Solution Preparation Acrylidone anionic polymers have been dissolved in aqueous alkaline solution according to following equation: WB= AAM.Mw 72 IX AA = Percent acrylic acid in polymer N = Percent neutralization desired (minimum is 30%) MW = Molecular weight of base in grams 72 = Molecular weight of acrylic acid WB = Weight of base in grams PVP or PVP-K-30, Polyvinylamides are highly polar, amphoteric polymers, which have been known since 1930s. The polymers derived from cyclic structures are more important. Poly (N-vinyl-2-Pyrrolidone), also called polyvinylpyrrolidone, povidone or PVP, is the only one available in commercial quantities. PVP exhibits a unique combination of properties, including solubility in water and in organic solvents, very low toxicity, good film-farming characteristics and the ability to adhere to a number of substrates. Solubility, PVP is readily soluble in cold water and the concentration is limited only by viscosity. PVP is also freely soluble in many organic solvents including alcohols, some chalinted compounds. The other chemicals used in this work, Bovine Serum Albumin (BSA, Mw=70.000, Fluka 96%) Copper Sulphate (CuS04. 5H20, Merck) Hydrocholoric Acid (HC1, Merck) Sodium Hydroxide (NaOH, Merck) Potasium Bromide (KBr, IR Grade-Merck) UV-visible absorbtion spectra was obtained at room temperature with a Shimadzu UV-160 A, recording spectrophotometer. The FT-IR spectrum of the products were obtained acquired with, a Jasko 5300 spectrophotometer. The pH-measurements were carried out using a WTW pH 523 digital pH- meter coupled with a WTW Type E 50 pH electrode. For conductometric measurement a WTW LF 95 digital conductometer was used. Solubilities of Polymer-Metal and Polymer-Metal-Protein Complexes Addition of copper ions didn't affect the solubility of PAA within a certain range of n^/ric values at pH 7. The phase separation in the system PAA-Cu(II) occurred only at some critical metal concentrations (nAA/nCu=25). The mixtures of BSA-Cu(II)-PAA remain in a wide range of nAA/npr soluble The amount of precipitate increase in proportion with the increase in n^/n,^. The absence of free protein molecules in matrix solution indicated that all the added protein molecules are strongly bound by the PMC, resulting in the formation soluble and insoluble ternary complexes PAA-Cu(II)-protein. It can be said that, when the ratio n^/iy > 1, protein free fractions of PMC remain in matrix solution. Synthesis of Polymer-Metal Complexes (PMC) Polymer was dissolved in water pH 7 and solid CuS04.5H20 was directly added to polymer solution while stirring at 20 °C then pH of solution was adjusted to about 7 and 3.5 and spectrophotometric properties were determined. PAA and PVP were prepared in the same way. AAP were dissolved in aqueous alkaline solution and then CuS04.5H20 was added to polymer solution while stirring at 20°C. COP50 was prepared like PAA and PVP. This copolymers dissolve readily in water since AA:VP ratio is 1:1. Synthesis of Ternary Complexes of PE-Metal-Protein, AAP-Metal-Protein Polymer (PAA) and COP50 were dissolved in water at pH 7 and added firstly protein then CuS04.5H20 to solution, pH of solution was also adjusted to 7. AAP (COP75, COP25) were dissolved in aqueous alkaline solutions and added protein then CuS04.5H20 to solution pH of solution was also adjusted to 7. Results of UV- Visible and FT-IR Spectra of Polymer-CuOD and Polymer Cu(II)-BSA Ternary Complexes PAA-Cu(H) complex was characterized by UV-Visible spectroscopy, absorbtion at 750 nm and 245 nm increase and solution become more and more deeply blue with increasing neutralization so the absorbance values increase with increasing pH. The infrared spectra of, PMC and PE-Metal-Protein ternary complexes have been taken as compared with PE spectra. These results have been shown in Table 1. As metal and BSA involve in complex structure, characteristic peaks of PAA become different and new peak occurs at about 1 150 which indicate the complex formation. Similarly peak at about 1550 cm"1 blending BSA, disappeared as complex formes. AAP and PVP-Cu(II) complexes were also characterized by UV-visible spectrophotometry. For all AAP, the absorbance increase linearly with increasing concentration of the copper ions and pH. For PVP the absorbance doesn't increase with increasing concentration of the copper ions either pH 4 or pH 7. This implies that cupric ions do not form complexes with PVP molecules. XI Table 1. Results of FT-DR. spectrophotometry. b : broad The infrared spectrum of AAP have been taken for comparison with AAP- Metal and AAP-Metal-BSA complexes. Results have been shown in Table 2. Table 2. Results of FT-IR Spectrophotometry. b : broad The similar results were obtained as mentioned before for copolymers.