Highly water repellent aerogels based on cellulose stearoyl esters

Abstract

Herein we combine in a novel way the physical effect of porous structure of a cellulosic aerogel with the chemical effect of long alkyl tails by a well known homogeneous green esterification method, to achieve purely bio-based and highly water repellent cellulosic materials. As an alternative for a traditional fluoro derivatized hydrophobization, here long fatty acid tails are utilized to lower the surface energy. To minimize the process emission, ionic liquid (IL) 1-allyl-3-methylimidazolium chloride is used for the esterification, due to its non-volatility and recyclability. We have shown here that low degree of substitution (DS) of the fatty acid cellulose material enables the spontaneous formation of aerogels. Additionally, the very low content of the long stearoyl tails combined with the porous aerogel structure resulted in significant increase in hydrophobicity from an aqueous contact angle of 0 up to 124 . We foresee that this approach can allow sustainable and completely bio-based coatings and insulators paving the way for a new green application potential for cellulose based materials.

Functional nanomaterials through esterification of cellulose: a review of chemistry and application

“…Such surfaces exhibited both excellent liquid repellency upon liquid impact and anti-icing properties (Chen et al 2014). Furthermore, a highly water-repellent aerogel was prepared using stearoylated NFC with a very low DS (\ 0.1) by supercritical CO 2 drying process (Granstrom et al 2011). Such aerogels maintained stable in water for 24 h without disintegration or collapse after drying.…”

“…pyridine and triethylamine, are applied (Heinze et al 2006). This procedure is widely used for the preparation of cellulose fatty acid esters with different lengths of aliphatic chains (Crepy et al 2011;de Menezes et al 2009;Granstrom et al 2011;Kulomaa et al 2015;Zhang et al 2015a, b). In the case of the esterification in pyridine, pyridine not only acts as the solvent, but also acts as a catalyst via forming a reactive intermediate driving the reaction forward.…”

Ultralight Industrial Bamboo Residue-Derived Holocellulose Thermal Insulation Aerogels with Hydrophobic and Fire Resistant Properties

“…To improve water and fire resistance, physical or chemical modifications via reinforcing components are effective modification methods. Many methods have been reported regarding flame retardant and hydrophobic modification, including: (1) cellulose nanofibril (CNF) aerogels were modified with methylene diphenyl diisocyanate (MDI) by solvent exchange [13]; (2) CNF aerogels were crosslinked with ionic liquid 1-allyl-3-methylimidazolium chloride for hydrophobic modification [14]; (3) CNF aerogels were coated on a silane modifier by chemical vapor deposition (CVD) [15]; (4) and CNF aerogels were modified with cationic chitosan (Ch), anionic poly(vinylphosphonic acid) (PVPA), and anionic montmorillonite clay (MMT) by a layer-by-layer technique [16]. However, these methods have complicated modification processes, and often do not pay attention to the durability of modifiers.…”

Fluorescent cellulose aerogels containing covalently immobilized (ZnS)x(CuInS2)1−x/ZnS (core/shell) quantum dots

“…Intriguing features such as densities ≤8 mg cm −3 (Liebner et al 2010 ), low heat transmission, high interconnected porosity (≤99.99 %) and void surface area (≤650 m −2 g −1 ) render cellulose aerogels promising materials for a large variety of technical applications. Potential fields of use are high-performance thermal insulation (Plawsky et al 2010 ), lightweight construction materials (Granstrom et al 2011 ), oil–water separation (Cervin et al 2012 ), photo-switchable (Kettunen et al 2011 ) or shape-recovering superadsorbers (Zhang et al 2012 ), bio-inspired cargo carriers on water and oil (Jin et al 2011 ), adsorption of pollutants from air and water, catalysis (Koga et al 2012 ), energy storage (Razaq et al 2012 ; Hu et al 2013 ), temporary templates (Korhonen et al 2011 ), hemodialysis (Carlsson et al 2012 ), controlled drug release in wound treatment (Haimer et al 2010 ), or regenerative therapies where cellulosic aerogels have been studied as artificial blood vessels (Klemm et al 2001 ), cartilage tissue (Bodin et al 2007 ), or cell scaffolding materials (Liebner et al 2011 ). Covalent immobilisation of quantum dots on the large inner surface area of cellulosic aerogels is a new approach that is considered to further expand the application potential of cellulosic aerogels.…”