Coordination Polymer: Synthesis, Spectral Characterization and Thermal Behaviour of Starch-Urea Based Biodegradable Polymer and Its Polymer Metal Complexes

Hindawi Publishing Corporation Bioinorganic Chemistry and Applications Volume 2010, Article ID 848130, 8 pages doi:10.1155/2010/848130 Research Article Coordination Polymer: Synthesis, Spectral Characterization and Thermal Behaviour of Starch-Urea Based Biodegradable Polymer and Its Polymer Metal Complexes Ashraf Malik,1 Shadma Parveen,1 Tansir Ahamad,2 Saad M. Alshehri,2 Prabal Kumar Singh,1 and Nahid Nishat2 1 Materials Research laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025, India 2 Department of Chemistry, King Saud University, Riyadh 1145, Saudi Arabia Correspondence should be addressed to Nahid Nishat, nishat Received 18 February 2009; Revised 19 July 2009; Accepted 30 March 2010 Academic Editor: Dimitris Kessisoglou Copyright © 2010 Ashraf Malik et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A starch-urea-based biodegradable coordination polymer modified by transition metal Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) was prepared by polycondensation of starch and urea. All the synthesized polymeric compounds were characterized by Fourier transform-infrared spectroscopy (FT-IR), 1 H-NMR spectroscopy, 13 C-NMR spectroscopy, UV-visible spectra, magnetic moment measurements, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). The results of electronic spectra and magnetic moment measurements indicate that Mn(II), Co(II), and Ni(II) complexes show octahedral geometry, while Cu(II) and Zn(II) complexes show square planar and tetrahedral geometry, respectively. The thermogravimetric analysis revealed that all the polymeric metal complexes are more thermally stable than the parental ligand. In addition, biodegradable studies of all the polymeric compounds were also carried out through ASTM standards of biodegradable polymers by CO2 evolution method. 1. Introduction Starch-based coordination polymers are known to be completely degradable in soil and water and can promote the degradation of nonbiodegradable material when blended or modified. Starch is one of the main natural polymers studied for the production of biodegradable materials [1]. Starch is a promising raw material because of its annual availability from many plants, its rather excessive production with regard to current need [2]. Because of environmental pollution problems caused by using synthetic polymers based on petrochemicals [3], the development of environment friendly polymeric material has attracted excessive interest [4]. A huge number of biodegradable polymers have been synthesized chemically or by microorganism and plants [5]. Depending on the origin, different categories of biodegradable polymers have been proposed. To list a few, there are agropolymers, such as starch or cellulose from agroresources, polymers obtained by microbial production, for example, polyhydroxyalkanoates, and chemically synthesized polymers from monomers derived from agroresources (e.g., polylactic acid). Chemically synthesized polymers from monomers obtained commercially by chemical synthesis. Among these, starch is potentially useful material for biodegradable material because of its natural abundance and low cost [6, 7]. Starch is the major carbohydrate in plant, tubes, and seed endosperm, where it is found as granule. Each granule contains several million amylopectin molecules accompanied by a much number of smaller amylase molecules. However, starch-based-materials have some drawbacks [8] including limited long-term stability caused by water absorption, aging caused by retrogradation, poor mechanical properties, and bad processability. To overcome these limitations, biodegradable polymers have been synthesized and modified. Our purpose of work was the modification of starch with urea for improving the properties and with some transition metals for enhancement in the characteristics and for synthesizing the coordination polymer. The applications of biodegradable polymers have been discussed on three major areas, namely, medical, agricultural and consumer goods packaging. Some of these have resulted in commercial products because of their specialized nature 2 and greater unit value. Medical device applications have developed faster than the other two and have been used as surgical implants in vascular and orthopedic surgery as implantable matrices for the controlled long-term release of drugs inside the body as absorbable surgical implants and for use in the eyes; some other applications are bone fixation devices and vascular grafts, adhesion prevention, artificial skin, drug delivery system, agricultural mulches controlled release of agricultural chemicals, agricultural planting containers, and packaging [9–12]. 2. Experimental 2.1. Materials. Starch, urea, ethanol MERCK (Mumbai), and sodium hydroxide were used without further purification. Solvents such as acetone, DMF, DMSO, and (s.d fine chemicals) methanol were purified by standard procedure before use. Manganese (II) acetate tetrahydrate [Mn(CH3 COO)2 · 4H2 O], copper (II) acetate monohydrate [Cu(CH3 COO)2 · H2 O], nickel (II) acetate tetrahydrate [Ni(CH3 COO)2 · 4H2 O], cobalt (II) acetate tetrahydrate [Co(CH3 COO)2 · 4H2 O], and zinc (II) acetate dihydrate [Zn(CH3 COO)2 · 2H2 O] were used without further purification. All the microorganisms were provided by C.S.A. Agricultural University, Kanpur. 2.2. Synthesis 2.2.1. Synthesis of Polymeric Resin. The polymeric resin was synthesized by polycondensation of urea and starch in alkaline medium in 1 : 1 molar ratio according to Scheme 1 [13, 14]. In a 250 mL three-necked round-bottomed flask, equipped with a stirrer and a condenser, 0.60 gm (0.01 mol) of urea and 1.62 gm (0.01 mol) of starch poured with 110 mL deionized water were placed, and then it was stirred with high speed (>1000 r/min) in a constant temperature water bath at 95◦ C for 3 h. The pH was adjusted to 8 with NaOH. The reaction was monitored by thin layer chromatography (TLC) using ethanol as an eluent. The resulting colorless viscous product was washed with ethanol and acetone and dried in a vacuum oven under reduced pressure at 50◦ C for 10 h. The white powder of starch-based polymer modified by urea (poly-SUr) was obtained in 70% yield. The synthesized product was found to be soluble in distilled water and DMSO and insoluble in some common organic solvents. 2.2.2. Synthesis of Metal Complexes. Metal complexes of polySUr were prepared by using molar ratio (1 : 1) of poly-SUr and metal salts. A typical procedure for the preparation of the Cu(II) complex is carried out as 2.22 gm (0.01 mol) of poly-SUr dissolved in a minimum quantity (∼25 mL) of hot DMSO and 1.99 gm (0.01 mol) of Cu(II) salt was dissolved in DMSO (∼20 mL) separately. Both solutions were filtered and mixed in hot condition with constant stirring. Then the (...truncated)