Self-assembly of curdlan molecules for the formation of thermally induced gels

The differences in the self-assembly process between cold-set (CCS) and heat -set (CHS) curdlan gels were investigated using micro-differential scanning calorimetry, atomic force microscopy, and small-angle X-ray diffraction. The results indicate that the triple-helix structure of curdlan dissociated into single helices in its suspension state (C-SUS) at 65 degrees C. Upon cooling to around 38 degrees C, these single helices assembled into long, thick fibers with a height of up to 11.50 nm, contributing to the gel structure of CCS. Heating C-SUS from 65 degrees C to 90 degrees C caused the single helices to transform into triple helices due to hydrophobic interactions. Subsequent cooling to 25 degrees C, led to the formation of short, thick bundles with a height of up to 8.78 nm, forming the network structure of CHS gel. As a consequence, CHS gels exhibited higher hardness and elasticity but lower fatigue resistance. This is attributed to an increased degree of physical cross-linking, as evidenced by a reduction in the size ( Xi) and spacing ( xi) of high-density domains within the gel structure, and a simpler mechanism of energy dissipation through alignment of the molecular chain segment. These findings are valuable for the design and development of curdlan-based gels with tailored mechanical properties.