Hydrogels Based on Starch from Various Natural Sources: Synthesis and Characterization

Hydrogels based on a graft copolymer of acrylic acid (AA) and acrylamide (AAm) on a backbone of starch, obtained from different natural sources, have been prepared and characterized for potential agricultural use, as soil moisture regulators and nutrient sources for plant nutrition. Five types of starch are used: corn, waxy corn, wheat, potato, and rice starch. Hydrogels are prepared by a solution polymerization method, in the presence of ammonium persulphate (PSA) as initiator and N,N'-methylene-bis-acrylamide (MBA) as a cross-linking agent. Thermal and physico-chemical properties, such as thermogravimetry analysis and differential scanning calorimetry data and swelling properties of hydrogels, are observed. The influences of the cross-linking agent on the swelling ratio (SR) and solubility of prepared hydrogels are studied and optimized. The highest SR observed in water corresponded to non-cross-linked hydrogels prepared with waxy corn starch (780 g water per g dry matter), and the SR of these hydrogels in ammonium sulfate and calcium nitrate solutions are 9.6 and 1.2 g per g dry matter, respectively. Higher thermal stability is observed with cross-linked starch-g-(AA-AAm) hydrogels. The non-cross-linked hydrogels have a higher SR, but also have significant solubility in water.Byly připraveny hydrogely na bázi roubovaného kopolymeru škrobu z různých přírodních zdrojů, kyseliny akrylové a akryl amidu. Připravené hydrogely byly charakterizovány pro agrochemické účely, jako regulátor vlhkosti nebo jako nosič živin pro výživu rostlin. Pro syntézu bylo použito pět různých škrobů: kukuřičný, voskový kukuřičný, pšeničný, bramborový a rýžový. Hydrogely byly polymerizovány v roztoku v přítomnosti persíranu amonného (iniciátor) a N,N'-methylen-bis-akrylamidu (síťovací činidlo). U hydrogelů byly stanoveny tepelné a fyzikálně-chemické vlastnosti za použití termogravimetrické analýzy a diferenciální skenovací kalorimetrie. Dále byl studován a optimalizován vlivy síťovacího činidla na bobtnací poměr (SR) a rozpustnost připravených hydrogelů. Nejvyšší SR byl stanoven ve vodě u nezesítěného hydrogelu připraveného s voskovým kukuřičným škrobem (780 g vody na g sušiny) a SR tohoto hydrogelu v roztocích síranu amonného byl 9,6 g na g sušiny a dusičnanu vápenatého byl 1,2 g na g sušiny. Vyšší tepelná stabilita je pozorována u zesítěných hydrogelů a naopak nezesíťované hydrogely měly sice vyšší SR, ale také větší rozpustnost ve vodě

Biopolymer-Based hydrogels for agriculture applications: Swelling behavior and slow release of agrochemicals

Hydrogels are cross-linked polymers that can absorb and hold largeamounts of water and aqueous solutions due to the presence of hydrophilic functional groups in their 3D network. These materials also serve as vehicles of different active compounds because they can regulate their release rate. Because of such properties, hydrogels are currently used in many areas including agriculture, mainly as water retention agents for soil conditioning, and as carriers of agrochemicals for their slow or sustained-release. However, most of the hydrogels currently available on the market are based on polyacrylamide and acrylate derivatives, which means that they are not completely biodegradable, i.e. are considered as potential soil contaminants and present certain degree of toxicity. In this context, the development of biodegradable hydrogels for their use in agriculture is gaining interest worldwide. Biopolymers such as chitosan, cellulose, alginate and their derivatives are being explored due to their biocompatibility, biodegradability and low cost. Briefly, in this chapter, recent studies on biopolymer-based hydrogels for their use in agriculture are discussed in terms of their synthesis, swelling behavior, as well as their uses for slow and controlled release of agrochemicals.Fil: Tomadoni, Bárbara María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Casalongue, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Alvarez, Vera Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin