Modification of Pea Starch and Dextrin Polymers with Isocyanate Functional Groups

Area of Science:

• Polymer Chemistry
• Materials Science
• Carbohydrate Chemistry

Background:

• Starch and dextrin are abundant biopolymers with diverse applications.
• Chemical modification can enhance the functional properties of starch and dextrin.
• Isophorone diisocyanate (IPDI) offers unique reactivity for polymer modification.

Purpose of the Study:

• To chemically modify pea starch and dextrin using IPDI.
• To characterize the modified polymers' chemical structure and thermal properties.
• To evaluate the impact of modification on moisture sorption behavior.

Main Methods:

• Modification of pea starch and dextrin with isophorone diisocyanate (IPDI).
• Confirmation of urethane and isocyanate functionalities using Fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance (13C NMR).
• Determination of the degree of substitution (DS) via elemental analysis.
• Thermal analysis including thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to assess thermal degradation and glass transition temperatures (Tg).
• Dynamic water vapor sorption analysis.

Main Results:

• Successful modification of starch and dextrin confirmed by FTIR and 13C NMR, indicating urethane and residual isocyanate groups.
• Higher degree of substitution (DS) observed in modified dextrin compared to modified starch.
• Improved thermal stability, evidenced by higher onset degradation temperatures and temperatures at maximum mass loss for both modified polymers.
• Reduced glass transition temperatures (Tg) in modified starch and dextrin, particularly noticeable in modified dextrin at high IPDI ratios.
• Significant reduction in moisture sorption for modified dextrin and a slight reduction for modified starch compared to their unmodified counterparts.

Conclusions:

• Isophorone diisocyanate (IPDI) effectively modifies pea starch and dextrin, introducing urethane linkages.
• The modification enhances thermal stability and alters glass transition temperatures.
• Modified dextrin demonstrates a more pronounced reduction in moisture sorption than modified starch, indicating potential for hydrophobic applications.