Water-soluble hydroxypropyl curdlan derivatives with thermosensitive properties.

Area of Science:

• Polymer Chemistry
• Biomaterials Science

Background:

• Curdlan, a bacterial polysaccharide, is poorly soluble in common solvents.
• Developing soluble and functional curdlan derivatives is essential for broader applications.

Purpose of the Study:

• To synthesize hydroxypropyl curdlan (HPCD) derivatives.
• To investigate the structure-property relationships, focusing on water solubility and thermo-responsive behavior.

Main Methods:

• Homogeneous etherification of curdlan with propylene oxide.
• Characterization using NMR spectroscopy (¹H, ¹³C, DEPT135, 2D HSQC).
• Thermal behavior analysis via rheology, turbidimetry, and ATR-FTIR spectroscopy.

Main Results:

• HPCD derivatives exhibit water solubility above a substitution degree of 1.
• Thermo-responsive characteristics were observed due to the balance of hydrophilic-hydrophobic groups.
• Rheological studies showed phase separation behavior similar to cellulose derivatives.
• ATR-FTIR revealed selective dehydration of side chains preceding main chain dehydration during heating.

Conclusions:

• Hydroxypropylation effectively enhances curdlan's water solubility and introduces thermo-responsiveness.
• HPCD exhibits unique thermal phase transition behavior driven by selective dehydration processes.
• These findings open avenues for novel applications of modified bacterial polysaccharides.