Directed Self-Assembly of Dumbbell-Shaped Cellulose Spherulites via Bottom-Up Approach

Polymer spherulites are typically fabricated by cooling or quenching crystallization, while their spherulitic growth and evolution mechanisms are still poorly understood. Herein, we successfully fabricated dumbbell-shaped cellulose spherulites for the first time and elucidated their formation mechanism. Specifically, chemical pulp was dissociated into colloidal particles as building blocks when pretreated with multicarboxylic acid deep eutectic solvents (DES) and homogenized. Following a direct bottom-up process, evaporation-driven self-assembly of colloidal particles into a cellulose spherulite with a “Maltese cross”-extinction pattern followed the oriented attachment mechanism. First, a series of colloidal particles formed nanospheres that connect end-to-end to assemble into dendrites, and then the step growth of spherulites involves small-angle branching and a radiating array of crystalline fibers to form dumbbell-shaped assemblies as spherulites. This work provides fundamental insights into the hierarchical evolution of cellulose spherulites, which are expected to serve applications in drug delivery, tissue engineering, and sensing.