Natural polymers associative thickeners

This chapter describes the main properties and methods for the characterization of polyelectrolytes derived from the biomass. The most important sources are plants, with cellulose and starch, which turn to polyelectrolytes after chemical modifications. CarboxymethylceUulose is the main cellulose derivative used in many industrial applications as good thickener and hydrophilic polymer for aqueous media. Cationic starches are mainly used in the paper industry for fiUa- retention or paper wet-strength. Natural polyelectrol5des are produced by algae with anionic alginates and carrageenans as the major representatives, which are used in food applications and for biomedical devices. In this respect, alginates are often associated in an electrostatic complex with a pseudo-natural polyelectrolyte (chitosan), a cationic polymer extracted from crustaceous shells. 

In the first system, the hydrophobic monomer included in the SDS micelle is polymerized in the same polymer chain, but most of the SDS is relarged in the serum in the second system, the hydrophilic part of the surfmer remains associated with the main polymer chain (Fig. 4). In contrast, if the surfmer is mixed with a nonpolymerizable surfactant, the surfmer xmits are randomly distributed in the polyacrylamide polymer (Fig. 5). Surprisingly, the thickening efficiency of that last system is a thousand times higher than the former, it is suggested that the difference is due to the intramolecular nature of the hydrophobic interactions, when the micelles contain the surfmer only. 

---