Degradation Kinetics of Some Coordination Biopolymers of Transition Metal Complexes of Alginates: Influence of Geometrical Structure and Strength of Chelation on the Thermal Stability

¹Department of Chemistry, Faculty of Science, Assiut University, Assiut, Egypt
 ²Chemistry Department, School of Science, Research Center of Materials Science, Nagoya, Japan

*Corresponding author: Refat M Hassan, Department of Chemistry, Faculty of Science, Assiut University, Assiut 71516 Egypt. 

Received: November 21, 2019
Published: December 18, 2019

ABSTRACT

Non isothermal  (TG) and (DTG)  thermal techniques have been applied for studying degradation  kinetics of some coordination biopolymers of transition metal complexes such as Mn(II)-, Co(II)-, Ni(II)-, Cu(II)- and Zn(II)-metal-ions coordinated with the carboxylate and hydroxyl functional groups of alginate  as a natural polymer.  Three stages of degradation for such complexes have been observed. The first one was corresponding to the dehydration of two coordinated water molecules, followed by degradation of the formed dehydrated derivatives in the two following stages, respectively. Metal oxalates were formed as intermediate fragments.  Sets of different models applied to compute the kinetic parameters of degradation. The kinetic results of degradation revealed that the stability was increased in the order Zn < Mn ≤ Co < Ni < Cu–alginates. A tentative degradation mechanism in terms of the complexes thermal stability, model structure, geometrical configuration and strength of chelation is discussed.

Keywords: Degradation; Transition Metals; Complexes; Kinetics; Thermal Stability