Plant-derived phytoglycogen nanoparticles are composed of highly branched chains of glucose, resulting in soft and compact nanoparticles with a highly porous, dendritic structure and rich hydroxyl surface character. The significant hydrophilicity of this material, coupled with hydrophobic surface functionalization, should allow for embedding of hydrophilic micronutrients within the internal pores, attachment to a hydrophobic leaf surface, and controlled release of these nutrients as a foliar fertilizer. Foliar feeding is an efficient method of nutrient delivery which mitigates nutrient loss to soil and leaching into aqueous environments. To this end, a series of hydrophobically-modified phytoglycogen nanoparticles have been prepared by a gas-phase reaction with hexanoyl chloride, creating esterified nanoparticles. A combination of XPS and elemental analysis has shown that initial functionalization occurs at the surface, while the bulk functionalizes only after longer reaction times. These results also show a fine degree of control over the degree of substitution by modulating the reaction time. Studies have also shown significant changes in solubility, size, and zeta-potential with functionalization. One-dimensional and two-dimensional NMR spectra of modified and unmodified phytoglycogen have also been collected. Additionally, the adsorption of Rose Bengal, a hydrophobic dye, has been used to compare the surface hydrophobicity of these modified nanoparticles with standard nanoparticles, such as fullerols and oxidized multi-walled carbon nanotubes. Results will also be presented on similar modification of cellulosic nanomaterials which show that hydrophobic surface functionalization can modulate release of embedded plant macronutrients.

Hydrophobic functionalization of glucose polymers for nutrient release

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ACS Fall 2022

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