Hydrogels Based on Natural Polymers Loaded with Bentonite and/or Halloysite: Composition Impact on Spectroscopic, Thermal, and Swelling Properties

Rodrigo César Sabadini; Mariana Fernandes; Verónica de Zea Bermudez; Agnieszka Pawlicka; Maria Manuela Silva

doi:10.3390/molecules29010131

Hydrogels Based on Natural Polymers Loaded with Bentonite and/or Halloysite: Composition Impact on Spectroscopic, Thermal, and Swelling Properties

Molecules. 2023 Dec 25;29(1):131. doi: 10.3390/molecules29010131.

Authors

Rodrigo César Sabadini^{1

2}, Mariana Fernandes³, Verónica de Zea Bermudez³, Agnieszka Pawlicka², Maria Manuela Silva¹

Affiliations

¹ Centro de Química e Departamento de Química, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
² Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador Sãocarlense 400, São Carlos 13566-590, SP, Brazil.
³ Department of Chemistry and CQ-VR, University of Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal.

Abstract

Hydrogels are characterized by their property of absorbing and releasing a high content of water and water-based liquids; thus, they can be applied in agriculture as controlled-release water and fertilizer products. The focus of this research was efficient and low-cost natural polymer-based hydrogels obtained by crosslinking gellan gum (GGLA) and starch (ST) with acetic acid (CA) and loading them with either bentonite (BET) and/or halloysite (HAL). The hydrogels were obtained by mixing 100, 75, 50, 25, and 0 wt.% of GGLA with 0, 25, 50, 75, and 100 wt.% ST water solutions. To obtain the networks, they were crosslinked with 10, 5, and 2 wt.% of CA and loaded with 2, 5, and 10 wt.% of BET and/or HAL. The samples were analyzed by infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), their swelling in water, and the state of bound water properties. The results of these analyses point to the formation of a polymeric network with a decomposition temperature of >250 °C, and tailorable swelling properties that vary between 3 and 77, depending on the hydrogel composition. In summary, GGLA-ST-BET/HAL hydrogels are a good option for eco-friendly agriculture materials.

Keywords: bentonite; gellan gum; halloysite; hydrogels; nanocomposites; starch.

Grants and funding

R. C. Sabadini was funded by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES) for the post-doctoral fellowship process 88881.172281/2018-01, and M. M. Silva by the Portuguese Foundation for Science and Technology (FCT) project UID/QUI/0686/2020. A. Pawlicka was funded by The Brazilian National Council for Scientific and Technological Development (CNPq; grant 310693/2021-7), and FAPESP (grants 2013/19297-3, 2014/17174-4 and 2013/07793-6).