Self-Assembly and Complexation of Cellulose Nanocrystals in an Amorphous Carrageenan-Polylactic Acid Solid

Cellulose nanocrystals (CNCs) are a sustainable and unique structure with a large surface area to form strong intermolecular interactions in biopolymeric matrices. However, fundamental self-assembly mechanisms underlying intermolecular interactions in CNCs between amorphous carrageenan and polylactic acid (PLA) remain poorly understood. This study investigated CNCs interactions with carrageenan and PLA in solution and amorphous solid, hypothesizing that incorporating CNCs into matrices enhances mechanical properties through strong interactions. Transmission electron microscopy revealed that the rodlike CNCs were nanoscale. X-ray diffraction identified the crystallographic structure of CNCs at (110) and (203). PLA was in the α-crystalline form, whereas carrageenan exhibited broad peaks, indicating a highly amorphous structure. 1 H nuclear magnetic resonance spectroscopy suggested that OH participated in intermolecular interactions in the CNCs, carrageenan, and PLA mixture biocomposite, consistent with hydrogen bonding, which enhanced the structural integrity, complexation, and reinforced mechanical strength to 50.70 MPa. Meanwhile, time-of-flight secondary-ion mass spectroscopy detected K +, Ca 2+, Na +, SO x – ions, and C x H y O z ± fragments from the biocomposite surfaces. 23 Na NMR suggested that ionic bridging interactions existed in the biocomposite matrix. Novel molecular interaction insights revealed from CNC incorporation into biocomposites.