Based on end use, there are various chemicals available those can hold water for longer time. Please let me know end use.

the gel with capsule architecture and hydrophilic properties.

Hi, I would look at clays more specifically at bentonite. It is inexpensive, non-toxic and high water binding capacity. In Thailand it is used on wide scale to improve arable land by keeping water bound to the soil. If you search on bentonite and agriculture you will find examples of use and required quantities.

Polyacrylamide

"The research team sought to replicate the key features of the cactus root system. To imitate the cactus root and its outer covering, they made a material composed of cellulose fibers, agarose cyrogel and microparticles. Then, they made a cylindrical-shaped gel and freeze-dried it to form a structure that mimics the layered composition of cactus root epidermis. Laboratory tests suggest that the resulting cactus-root-inspired material (CRIM) is capable of absorbing water nearly 930 times faster than it loses through evaporation.

The researchers say the mixture of cellulose fibers, microparticles and cryogel is adjustable for particular needs. For example, adding water-repellant microparticles to this system could produce CRIMs useful in oil separation and other oil-based engineering processes. They conclude that CRIMs could eventually have a host of applications in agriculture, cosmetics and medicine."

📷 Explore further: Certain species of trees retain stored water, limit root growth to survive three months without water

More information: Hyejeong Kim et al. Fast and Efficient Water Absorption Material Inspired by Cactus Root, ACS Macro Letters (2018). DOI: 10.1021/acsmacrolett.8b00014

Read more at: https://phys.org/news/2018-04-cactus-roots-creation-water-retaining-material.html#jCp

for a gel sodium polyacrylate or carbomer

Thank you all for nice discussion

hyaluronic acid hydrogel