Preparation and characterization of active polymers

A novel biodegradable sodium carboxymethyl cellulose (NaCMC)-based hydrogel was synthesized by using fumaric acid (FA) as a crosslinking agent at various ratios. Hydrogels which were crosslinked by fumaric acid as crosslinking agent (CMCF) were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differantial Scanning Calorimetry (DSC), X-Ray Diffraction Analysis (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Swelling behaviours of hydrogels were investigated in distilled water, various salt concentrations in water and pH solutions. The FTIR results indicated the crosslinking via ester formation between carboxyl groups of FA and hydroxyl group of NaCMC. The effect of FA concentration on roughness, swelling, degradation temperature, crystallinity of hydrogel structure and surface morphology of films were investigated. AFM analyses show that roughness of hydrogel surface was decreased with increasing crosslinking concentration. Crosslinking of CMC with FA leads to slightly increase in the maximum degradation temperature. Crystallinity of NaCMC was increased with crosslinking but slightly decreased with increasing crosslinker concentration. SEM images of hydrogels don?t give explicit information about surface morphology of hydrogels. Swelling studies in distilled water show that swelling degree of hydrogel was decreased with increasing crosslinking concentration. Swelling behavior of hydrogels was investigated in different salt and pH solutions as well. Besides, reversible pH-responsiveness of CMCF hydrogels were achieved but temperature not. From swelling studies in different salt solutions it was understood that the swelling capacity was decreased with an increase in charge of the metal cation [Al (3+) < Ca (2+) < Na (+)]. CMCF hydrogels containing the greatest ratio of FA exhibited the longest biodegradation time with a half life of 21 h using cellulase.