HCNCs as reinforcing paper additives. SEM micrographs of (A) an untreated paper, (B) a paper reinforced with an AZC-cross-linked CNC–biolatex composite, and (C) a paper reinforced by AZC-cross-linked ENCC–biolatex composite. Dynamic mechanical analysis (DMA) of reinforced papers, furnishing storage and loss moduli at T ∼ 25 °C (blue) and T ∼ 75 °C (red) at varying relative humidity (RH). (D) The untreated paper has storage and loss moduli (∼80 MPa and ∼2.4 MPa, respectively) that are almost invariant with respect to temperature and RH. (E) The AZC-cross-linked CNC–biolatex composite enhances the mechanical properties of paper by more than 500% compared with the pristine paper. (F) The ENCC–biolatex composite cross-linked with AZC enhances the mechanical properties of paper by ∼500% compared with the CNC–biolatex–AZC system and ∼1000% with respect to the untreated paper. Arrows indicate the axis of reference for the data. (Panels A–F) Adapted from ref. 82 with permission from American Chemical Society, Copyright 2018.