The naturally occurring hydrocolloids are widely used in various industrial sectors as rheological modifiers, thickening and gelling agents, flocculants, encapsulating agents, stabilisers of emulsions, foams and dispersions, etc. Recently, various types of nanocellulose (NC) such as nanofibrillated cellulose (NFC), cellulose nanocrystals (CNCs), and bacterial cellulose haves further expanded this group of materials. Although chemically modified NCs (particularly hydrophobized NCs) have attracted significant interest in the field of polymer (nano)composites, studies of hydrophobized NCs in water-based systems have received relatively little attention. In this contribution, hybrid gels based on polysaccharide hydrocolloids and hydrophobized NCs has been studied. Hydrophobized CNCs and NFC were prepared by covalent binding of alkylamines to the surface of NCs activated by periodate oxidation. Helical polysaccharides (starch, <i>i</i>-carrageenan, and xanthan gum) were used with the intention to harness their known ability to form inclusion complexes with hydrophobic substances. Moreover, a moderately hydrophobic cellulose, hydroxypropyl methylcellulose (HPMC), was used as a hydrocolloid polymer that can be involved into associative interactions, driven by the hydrophobic interactions. The combinations of such hydrocolloid polymers and hydrophobized NCs allowed utilization of hydrophobic interactions for alteration of gelation and gel properties of hybrid supramolecular and colloidal hydrogels. The stiffness and viscosity of hydrogels of starch, <i>i</i>-carrageenan and HPMC with hydrophobized NCs were enhanced in comparison with hydrogels incorporating parent unmodified NCs. Thus, exploitation of hydrophobic interactions allowed the building of more robust hybrid gels of helical and moderately hydrophobic water-soluble polysaccharides. Hydrophobized NCs enhanced the thermal response in hybrid HPMC hydrogels. Adhesion of starch to the surface of hydrophobized NCs has been confirmed by AFM. Structure and interactions in hydrocolloid polymer/NCs systems were studied using SAXS, SANS, AFM and NMR spectroscopy. Assembly of hydrocolloids with hydrophobized NCs driven by hydrophobic interactions has proven to be a versatile tool for modifying rheological properties of the systems based on hydrocolloid polymers.

Gelation in natural hydrocolloid composites incorporating hydrophobized nanocellulose

2019 Spring National Meeting

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