Hydrogels have gained a lot of attention with their widespread use in different industrial applications. The versatility in the synthesis and the nature of the precursor reactants allow for a varying range of hydrogels with different mechanical and rheological properties. Understanding of the rheological behavior and the relationship between the chemical structure and the resulting properties is crucial, and is the focus of this review. Specifically, we include detailed discussion on the correlation between the rheological characteristics of hydrogels and their possible applications. Different rheological tests such as time, temperature and frequency sweep, among others, are described and the results of those tests are reported. The most prevalent applications of hydrogels are also discussed.

Starch is a polysaccharide widely present in nature and characterized by a wide range of applications. This often implies the necessity for various novel properties with respect to those of native starch, mainly achievable via chemical modification. During the last decades, products with new or enhanced properties were prepared from starch because of the adoption of "green" solvents (ionic liquids and supercritical CO2) and several new techniques (regioselective derivatization, atom transfer radical polymerization, etc.) that are characterized by controlled modification. However, reviews on these works seem very rare. In this article, the application of ionic liquids and supercritical CO2 in the modification and processing of starch is summarized. The development of regioselective derivatization and controlled grafting of starch are also reviewed in the second part of this article.