The development of environmentally friendly hollow capsules holds a great promise for various advanced applications. Preparation of such spherical structures using renewable and sustainable resources is particularly attractive, where the development is driven by an increased global interest in new generations of green products that can meet the demands of the modern society. Cellulose is one of the most abundant biopolymers, which owing to its supramolecular structure possesses excellent material properties such as mechanical strength and chemical stability. As already demonstrated in the literature [1, 2], hollow capsules can be made by drop-wise precipitation of a gas-saturated solution of cellulose in a non-solvent. These capsules exhibit good mechanical and diffusion properties. In this study we take a step forward and perform a chemical modification of the cellulose used that will enable the capsules to significantly expand when they are exposed to an external stimulus, in the present case a decreased external pressure. As a first step to achieve this purpose, we apply a partial derivatization of native cellulose fibers to dialcohol cellulose before dissolution in LiCl/DMAc. In this way we explore the potential for using a heterogeneously modified structure of cellulose that on the molecular level increases the flexibility of the capsule shell. The expansion of the capsules was observed with a high-speed camera, and shell morphology and thickness were studied using scanning electron microscopy. Cellulose modification in the capsules was shown by reaction of periodate-oxidized cellulose with hydroxylamine hydrochloride, as well as by FTIR and solid state 13C NMR measurements. The results demonstrate that the dialcohol-cellulose-containing capsules expanded significantly more than the ones made solely of native cellulose.

Wet-expandable cellulose-based capsules

2019 Spring National Meeting

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