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Phthalates are the most prevalent plasticizers in poly(vinyl chloride) (PVC), the most commonly used polymer for drinking water distribution pipes. Though typically considered inert to the free chlorine necessary for drinking water disinfection, we found that certain commercially relevant phthalates leach from PVC and transform in the presence of free chlorine. The extent of aqueous phthalate leaching was alkyl chain length-dependent; the greatest leaching was observed for the most soluble 1-carbon chain phthalate, which was unaffected by free chlorine. In contrast, 2- and 4-carbon chain phthalates leached significantly less, and their concentrations decreased further in the presence of free chlorine. These observations were rationalized by experiments showing increased chlorine consumption with increasing phthalate alkyl chain length, indicative of structure-dependent chemical transformations of the parent phthalate with free chlorine. Using gas and liquid chromatography, high-resolution mass spectrometry, and nuclear magnetic resonance spectroscopy, we identified 13 disinfection byproducts of diisobutyl phthalate, 2 of which were confirmed using reference materials. The presence of both chlorinated and hydroxylated transformation products suggests reactions with both free chlorine and chlorine-derived reactive intermediates. This study underscores the need for consideration of chemical structure in predicting phthalate reactivity and highlights potential exposure risks in drinking water infrastructure. 

A suite of acyl chloride structural isomers (C6H11OCl) was used to effect gas-phase esterification of starch-based phytoglycogen nanoparticles (PhG NPs). The surface degree of substitution (DS) was quantified using X-ray photoelectron spectroscopy, while the overall DS was quantified using 1H NMR spectroscopy. Gas-phase modification initiates at the NP surface, with the extent of surface and overall esterification determined by both the reaction time and the steric footprint of the acyl chloride reagent. The less sterically hindered acyl chlorides diffuse fully into the NP interior, while the branched isomers are restricted to the near-surface region and form self-limiting hydrophobic shells, with shell thicknesses decreasing with increasing steric footprint. These differences in substitution were also reflected in the solubility of the NPs, with water solubility systematically decreasing with increasing DS. The ability to separately control both the surface and overall degree of functionalization and thereby form thin hydrophobic shells has significant implications for the development of polysaccharide-based biopolymers as nanocarrier delivery systems. 

Enhancing the delivery efficiency of NPK fertilizers benefits both crops and the environment through moderating the supplied dosage of nutrients in the soil, avoiding side reactions, maximizing absorption by the plant, and minimizing leaching and runoff. Bio-based materials such as cellulose are ideal scaffolds for nutrient delivery due to their inherent biocompatibility, biodegradability, and significant water uptake. In this work, nanocellulose-based hydrogels were regenerated from mixed softwood in acidic media and loaded with NPK by immersion in varied concentrations of an NPK-rich fertilizer solution. High loading of NPK was achieved within the hydrogel, but immersion in the matrix provided only slight slowing of nutrient release compared to rapid solubility of conventional formulations. Densification, crosslinking, and coating of the hydrogels with beeswax were ineffective strategies to further slow NPK release. Following these results, both gas and solution-phase esterification reactions of the cellulosic matrix with hexanoyl chloride were performed after NPK loading to introduce a hydrophobic surface layer. While solution-phase modification led to phosphorus leaching and was overall ineffective in altering nutrient release, the gas-phase modification slowed the release of P and K by more than an order of magnitude. Moreover, it was found that varying both the properties of the hydrophobic surface layer and the nutrient loading provide a means to tune release rates. Overall, this work demonstrates the potential of nanocellulose-based hydrogels to be used as an environmentally safe and sustainable vehicle for the controlled release of nutrients in agricultural applications.