Controlled Synthesis of Spherical Regenerated Nanocellulose and Its Structure–Property Relationships in Pickering Emulsions and Phase-Change Materials

Nanocellulose plays a pivotal role in advancing sustainable high-performance materials and expanding green development pathways across diverse sectors. Among these, spherical nanocellulose offers unique advantages in interfacial assembly compared to rod-like or fibrous morphologies. However, due to the difficulty in controlling the self-assembly process during its preparation, precise control of the spherical morphology remains a challenge. This work proposes a method combining carboxyl modification with dissolution-regeneration. By utilizing the electrostatic repulsion and steric hindrance effects of carboxyl groups to suppress the parallel aggregation of cellulose molecular chains, the controlled formation of a spherical morphology is achieved. In conjunction with mechanical processing, spherical regenerated nanocellulose (QRC) with a size of 77 nm was obtained at an ultrasonication time of 30 min. The absolute value of the ζ-potential of QRC is 30 mV. The spherical morphology and small aspect ratio of QRC enable it to serve simultaneously as a Pickering emulsifier and an aerogel self-assembly unit, achieving efficient encapsulation of n-octadecane (C18) (encapsulation efficiency of 84.9%, thermal storage efficiency of 104.4%). This strategy highlights the unique advantages of the spherical morphology and further expands the potential for green applications of nanocellulose in phase-change materials.