## 3 Plant-Based Biopolymers
### Cellulose-Based VMAs  
Cellulose, an omnipresent biopolymer, holds the distinction of being the Earth's most abundant natural substance, with an impressive annual production of approximately 2 \(\times\) 10\({}^{11}\) tons [19; 20]. It serves as the fundamental structural foundation of cell walls for a multitude of life forms, spanning the realms of plants, seaweeds, protists, and fungi [20; 21]. Often combined with hemicellulose from hardwoods and cotton, cellulose exhibits diversity, imparting distinct characteristics. Moreover, hemicellulose (xylan and glucomanan) have demonstrated the potential to create bioinspired nanocomposites with promising functional properties, particularly in enhancing barrier properties. Additionally, their strong affinity to cellulose within native plant cell walls is widely recognized [22]. At its core, cellulose manifests as a macromolecule, presenting an elongated, unbranched chain of variable length [20]. Its structure unfolds as a linear \(\beta\)-(1\(\rightarrow\)4)-linked glucan structure, marked by a remarkable ability to foster cooperative networks of intra- and intermolecular hydrogen bonds, creating a robust, water-resistant framework of fibrils and fibers (Figure 7) [23]. However, to reveal its pure form, cellulose, entwined with the complex cell walls of plants, must undergo liberation from its entangled companions, notably lignin and hemicellulose, through the alchemical process of pulping [8]. Natural cellulose typically exhibits a degree of polymerization (DP) above 1 \(\times\) 10\({}^{4}\), corresponding to a substantial molecular weight of roughly 2 \(\times\) 10\({}^{6}\) g\(\cdot\)mol\({}^{-1}\). Moreover, cellulose's versatility depends on three critical factors: molecular mass, degree of substitution (DS), and the chemical composition of the substitution group. As molecular mass increases, solubility decreases, while shear-thinning behavior intensifies [8]. Furthermore, cellulose has found extensive applications in various industrial sectors (food, cosmetics, pharmacy, latex paints, and ceramics) [24]. Particularly in the field of construction materials, the chemical modification of cellulose is recognized as a crucial step to unlock its full potential and achieve desired outcomes in cementitious materials [20; 23]. Indeed, in cement-based materials, cellulose serves as a VMA, primarily in the form of ether derivatives, with an annual usage tallying around 1 \(\times\) 10\({}^{5}\) tons in dry mortars [25]. These versatile derivatives play a multitude of roles in construction, including thickening, binding, and water retention [23]. When incorporated into cementitious materials, cellulose ethers increase viscosity and water retention capacity, reduce the yield stress, and improve shear-thinning behavior [24]. Additionally, it has been reported that the effectiveness of cellulose-based VMAs in modifying the properties of cementitious materials depends on several factors, such as the type of cellulose ether used, as well as its concentration, molecular substitution, molecular weight, and chemical composition [24; 26]. Additionally, [PERSON] et al. highlight the influence of other intrinsic parameters of cementitious materials, such as pH and ion levels in the cement paste [27; 28]. Furthermore, other studies have shown that the behavior of cellulose incorporated in cementitious materials varies depending on the nature of the superplasticizer with which it is combined. [PERSON] et al. investigated the impact of a cellulose-based VMA on the properties of cement pastes containing two different types of superplasticizers: polynaphthalene sulfonate (PNS) and polymelamine sulfonate (PMS). It was found that while the combination of cellulose VMA with PNS did not significantly affect rheological parameters, the presence of cellulose with PMS led to a notable increase in both viscosity and yield stress. Other differences were observed also between the two cement pastes, particularly in terms of bleeding, leaching, setting time, and compressive strength development.