Nanocellulose-stabilized Pickering emulsions for microencapsulation of phase-change materials

Abstract

Encapsulation of phase change materials (PCMs) is an important task in advanced thermoregulatory applications. A versatile approach is the formation of an impermeable composite shell around a PCM core through the polymerization of Pickering emulsions. Adsorption of nanocrystalline cellulose (NCC) or nanofibrillar (NFC) cellulose at the oil-water interface, and the introduction of diisocyanates into the oil phase, allow for the formation of a durable shell via urethane/amide bonding. This method differs from traditional emulsion polymerization in that it does not require the introduction of surfactants or an additional monomer to the aqueous phase. Cellulose acts as both a stabilizer and source of functional groups for crosslinking during the reaction with diisocyanate. The presence of six hydroxyl groups per cellulose monomer results in a highly functionalized oligopolyol, leading to the formation of rigid polyurethane. The structure is characterized by a high density of "hard" domains from urethane groups and the absence of "soft" polymer segments in the CNC structure. In contrast, NFC has both crystalline and amorphous segments, enabling the formation of an elastic shell. The surface modification of NFC with carboxyl groups allows control of adsorption at the interface, varying the ionic strength of the aqueous medium, which tunes the thickness of the resulting capsule and the phase transition, thermal stability, and elution of encapsulated PCM.
This work was supported by the Ministry of Science and Higher Education of the Russian Federation (project № FSZE 2023-0005).

Speaker

Dr. Denis Voronin
National University of Oil and Gas «Gubkin University»
Russia

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