Surface modification of cellulose nanocrystals (CNC) have been well-studied for the possible tuning of the CNC properties and applications. One of the properties that is affected by CNC surface modification is their interactions among themselves and with other moieties. In this study, CNCs were modified by an autocatalyzed esterification using (4-chlorosulfonyl) benzoic acid, which results in anionic benzosulfonyl grafts on the CNC surface. The reaction mechanism follows a tosyl chloride-catalyzed esterification. However, (4-chlorosulfonyl) benzoic acid contains both the catalyst and a carboxylic acid required for the esterification. As the intermediate sulfonyl ester is replaced with a more stable ester bond, the sulfonyl group is left pointing outwards in the final product. The degree of substitution could be tuned by the reaction time and the amine co-catalyst (pyridine, triethylamine, and diisopropylethylamine). The maximum degree of substitution reached was 0.3 which roughly translates to a surface degree of substitution of 1. Additionally, due to the acidic nature of the sulfonyl, the protonated amine co-catalyst remained in the product as the sulfonyl counter ion. The counter ion was found to affect the interactions between CNCs and hence their colloidal stability. Therefore, the counterion-sulfonyl interaction were investigateds by isothermal titration calorimetry and correlated with the degree of substitution and acid content. Finally, CNC interactions with di- and tetravalent ammonia were also investigated.

Sulfonyl-modification of cellulose nanocrystals and their interactions in aqueous media

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.