Dual modification of starch nanocrystals via crosslinking and esterification for enhancing their hydrophobicity

• Starch nanocrystals (SNCs) were modified by crosslinking and followed esterification.
• The dual modification led to much higher DS than single esterification modification.
• SNCs showed lower polarity and stronger hydrophobicity after the dual modifications.
• Crystalline structure of SNCs survived after the dual modifications.
• The dual modification will broaden applications of SNCs.

The aim of this study was to enhance the hydrophobicity of starch nanocrystals (SNCs) and improve their dispersibility in non-polar solvents through dual modifications. The dual modifications were carried out by crosslinking first and then followed esterification. The results of characterizations showed that the dual modifications resulted in a higher degree of substitution of SNCs than single esterification modification. The SNCs with the dual modifications possessed lower polarity and showed stronger hydrophobicity than the SNCs with single crosslinking or esterification modification and therefore could be dispersed in non-polar solvents such as chloroform, dichloromethane and toluene. In addition, the crosslinking protected the crystalline structure of SNCs being disrupted in the followed esterifications. The modified SNCs can be used as reinforcements for nanocomposites with hydrophobic polymer matrices or emulsion stabilizers and rheology modifiers.

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