Author(s): Gonçalves, Maria Gabriela Afonso ; Faria, Bruno Miguel Silva ; Moraes, Izabel Cristina Freitas ; Hilliou, L.
Date: 2025
Persistent ID: https://hdl.handle.net/1822/95074
Origin: RepositóriUM - Universidade do Minho
Subject(s): Carrageenan; Hydrogel; Molecular mass; Shear storage modulus
A set of carrageenans produced in the potassium form and with chemical structures varying from pure iota-carrageenans to nearly pure kappa-carrageenans is submitted to ultrasonication to reduce their molecular masses Mw while maintaining a constant chemical structure and a polydispersity index around 2. The kinetics of ultrasound-induced chain scission are found to be slower for polysaccharides richer in kappa-carrageenan disaccharide units. From the elasticity of samples directly gelled in a rheometer at 1 w/v% in 0.1 M potassium chloride, a critical molecular mass Mc is identified as the mass below which no gel can be formed. Mc is found to be smaller for kappa- and kappa-2-carrageenans of the order of 0.13-0.21 MDa. The presence of more sulphated disaccharide units significantly increases Mc up to 0.28 MDa for iota-carrageenan and 0.57 MDa for a highly sulphated hybrid carrageenan. For the set of Mw and carrageenans tested, no plateau in the Mw dependence of the gels' elasticities is found.
