Synthesis and characterization of PEGylated cellulose nanocrystals

Cement-based materials with low water-to-cement ratio, represented by high-performance concrete (HPC) and ultra-high-performance concrete (UHPC), exhibit excellent mechanical properties and durability. However, they suffer from issues such as insufficient and nonuniform cement hydration and severe autogenous shrinkage. In this study, Polyethylene glycol (PEG, 1500 g/mol) was grafted onto cellulose nanocrystals (CNCs) to synthesize PEGylated CNCs (PCNCs), aiming to solve the above issues through mechanisms such as short-circuit diffusion, steric hindrance, and internal curing. FTIR and NMR confirmed successful grafting. PCNCs exhibited increased crystallinity (70.21% to 72.59%) compared to CNCs, suggesting enhanced structural stability. TGA revealed higher thermal stability: onset decomposition temperature rose from 204 °C (CNCs) to 234 °C (PCNCs), with maximum mass loss at 303 °C (compared with CNCs: 280 °C). The absolute value of zeta potential of PCNCs is 13.3 mV ± 0.9 mV, with the proportion of aggregated particles (> 170 nm) reduced from 45.22 ± 2.5% (CNCs) to 4.53 ± 0.8%, indicating excellent colloidal stability and dispersibility in aqueous phases. TEM results further revealed that PCNCs are less prone to aggregation through synergistic electrostatic repulsion and steric hindrance. This study establishes a solid foundation for the future application of PCNCs in cement-based materials with low water-to-cement ratio.