Synthesis and characterization of carboxymethyl derivatives of kappa-carrageenan

Carboxymethyl derivatives of kappa-carrageenan (KC) with varying degrees of substitution were obtained by multi-step carboxymethylation process. The structural and chemical profiles of the derivatives were determined by FT-IR, 13C NMR, gel permeation chromatography (GPC), elemental analysis, potentiometric titration and visual estimation of gelation temperature. The derivatives exhibited high degrees of substitution (DS) and acidity. However, sulfur content, molecular weight (Mw) and gelation temperature were lower compared to the parent KC polymer. FT-IR confirmed the presence of carboxymethyl (CM) groups in the polymer backbone while 13C NMR revealed that functionalization occurred at the three hydroxyl groups in kappa-carrageenan disaccharide unit.