NaCl and KCl phase diagrams of kappa/iota-hybrid carrageenans extracted from Mastocarpus stellatus

• Phase diagrams of kappa/iota-hybrid carrageenan (KI) are different from a mixture of kappa- and iota-carrageenan (K + I).
• KI forms gels in KCl with no water synaeresis, in contrast to K + I.
• KI and K + I gels show strain hardening and KI gels can accommodate more NaCl.
• Strain at break of KI gels does not show salt specificity in contrast to K + I gels.
• In NaCl, K + I gels are more brittle than KI gels.

The phase diagrams of kappa/iota-hybrid carrageenan (KI) in KCl and NaCl are reported for the first time, together with the large strain properties of obtained KI gels. KI shows salt specificity as phase diagrams in KCl and NaCl are different. These diagrams do not comply with those of a mixture of kappa- and iota-carrageenan (K + I). Concentrated KI solutions in NaCl up to 0.3 mol/L exhibit viscoelastic properties reminiscent from entangled neutral polymers with no aggregation. Both KI and K + I gels are strain hardening, and show a concentration scaling of the elasticity with exponents ranging from 1.2 to 3.2 depending on the type of salt and ionic strength. The strain at break of KI gels does not show salt specificity in contrast to K + I gels. In NaCl, KI gels are less brittle than K + I gels. In KCl, KI gels show the same level of strain at break as the corresponding carrageenan mixture.

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