Swelling studies of copolymeric acrylamide/crotonic acid hydrogels as carriers for agricultural uses

Abstract

In this study, highly swollen acrylamide/crotonic acid hydrogels (in a rod form) containing some inorganic salts such as ammonium nitrate, potassium nitrate and ammonium sulphate used as fertilizer, an agricultural drug such as Dalapon (sodium 2,2-dichloropropionate) and two crosslinkers such as ethylene glycol dimethacrylate and 1,4-butandiol dimethacrylate were prepared by copolymerization of acrylamide and crotonic acid with g-radiation. As a result of swelling tests, the influence of g-ray dose and relative content of crotonic acid on the swelling properties, the diffusional behavior of water, diffusion coefficients and network properties of the hydrogel systems were examined. Acrylamide/crotonic acid hydrogels containing these salts and agricultural drug were swollen in the range 2045±400% in water, while polyacrylamide hydrogels swelled in the range 660±700%. Water intake of hydrogels followed a nonFickian-type diffusion.

Poly(acrylic acid/acrylamide/sodium humate) superabsorbent hydrogels for metal ion/dye adsorption: Effect of sodium humate concentration

“…Table II and Figure 5 clarifies that the swelling exponent n for the samples with varying SH concentrations lie between 0.68 and 0.79; thus suggesting the anomalous or non‐Fickian type diffusion 37. It is explained as a consequence of the slow relaxation rate of the polymer matrix, or rates of solvent diffusion and polymer relaxation are comparable 38. As solvent diffuses into the hydrogel, rearrangement of chains does not occur immediately.…”

Poly(acrylic acid/acrylamide/sodium humate) superabsorbent hydrogels for metal ion/dye adsorption: Effect of sodium humate concentration

“…Table II and Figure 5 clarifies that the swelling exponent n for the samples with varying SH concentrations lie between 0.68 and 0.79; thus suggesting the anomalous or non‐Fickian type diffusion 37. It is explained as a consequence of the slow relaxation rate of the polymer matrix, or rates of solvent diffusion and polymer relaxation are comparable 38. As solvent diffuses into the hydrogel, rearrangement of chains does not occur immediately.…”

Comparison of rigid divinylbenzene with flexible 1,7‐octadiene crosslinks in acrylic acid resins—effects on kinetics of swelling and loading of heavy metal ions from water

“…The value of the diffusion exponent ( n ) is greater than 0.50 in the case of all resins synthesized in this study. So, the diffusion is non‐Fickian, where diffusion and relaxation are said to be isochronally effective . It is explained as a consequence of slow relaxation of the polymer matrix …”

Swelling behavior and diffusion studies of high‐water‐retaining acrylamide/potassium methacrylate hydrogels

“…A fundamental and well‐accepted property of hydrogels, or SAPs, is their swelling behavior in aqueous, salt, and water‐soluble organic solutions 4–15. The swelling measurements are the main characteristic parameters for any hydrogel.…”

“…Table II shows that higher S % values were obtained when the KMA content was increased in the copolymeric chains. The increment in S % values was due to the more hydrophilic nature of the incorporated chemical groups (COO − K + ) 4–15. This was due to induction of electrostatic repulsion forces of the ionic charges of networks 4–15…”

“…The swelling kinetics of the copolymers varied as the nature of the chemical groups (e.g., hydroxyl, carboxyl, carbonyl, amide, and amine) changed in the AAm copolymer chains. This was mainly due to the many types of polymer–solvent interactions 4–8, 35, 36, 57 . r i , k S , and the theoretical equilibrium swelling ( S eq ) values of the hydrogels were calculated from the slope and intersection of the lines, as shown in Figure 6.…”

Poly(acrylic acid/acrylamide/sodium humate) superabsorbent hydrogels for metal ion/dye adsorption: Effect of sodium humate concentration

“…Table II and Figure 5 clarifies that the swelling exponent n for the samples with varying SH concentrations lie between 0.68 and 0.79; thus suggesting the anomalous or non‐Fickian type diffusion 37. It is explained as a consequence of the slow relaxation rate of the polymer matrix, or rates of solvent diffusion and polymer relaxation are comparable 38. As solvent diffuses into the hydrogel, rearrangement of chains does not occur immediately.…”

Comparison of rigid divinylbenzene with flexible 1,7‐octadiene crosslinks in acrylic acid resins—effects on kinetics of swelling and loading of heavy metal ions from water

“…The value of the diffusion exponent ( n ) is greater than 0.50 in the case of all resins synthesized in this study. So, the diffusion is non‐Fickian, where diffusion and relaxation are said to be isochronally effective . It is explained as a consequence of slow relaxation of the polymer matrix …”

Swelling behavior and diffusion studies of high‐water‐retaining acrylamide/potassium methacrylate hydrogels

“…A fundamental and well‐accepted property of hydrogels, or SAPs, is their swelling behavior in aqueous, salt, and water‐soluble organic solutions 4–15. The swelling measurements are the main characteristic parameters for any hydrogel.…”

“…Table II shows that higher S % values were obtained when the KMA content was increased in the copolymeric chains. The increment in S % values was due to the more hydrophilic nature of the incorporated chemical groups (COO − K + ) 4–15. This was due to induction of electrostatic repulsion forces of the ionic charges of networks 4–15…”

“…The swelling kinetics of the copolymers varied as the nature of the chemical groups (e.g., hydroxyl, carboxyl, carbonyl, amide, and amine) changed in the AAm copolymer chains. This was mainly due to the many types of polymer–solvent interactions 4–8, 35, 36, 57 . r i , k S , and the theoretical equilibrium swelling ( S eq ) values of the hydrogels were calculated from the slope and intersection of the lines, as shown in Figure 6.…”

Poly(acrylic acid/acrylamide/sodium humate) superabsorbent hydrogels for metal ion/dye adsorption: Effect of sodium humate concentration

“…Table II and Figure 5 clarifies that the swelling exponent n for the samples with varying SH concentrations lie between 0.68 and 0.79; thus suggesting the anomalous or non‐Fickian type diffusion 37. It is explained as a consequence of the slow relaxation rate of the polymer matrix, or rates of solvent diffusion and polymer relaxation are comparable 38. As solvent diffuses into the hydrogel, rearrangement of chains does not occur immediately.…”

Comparison of rigid divinylbenzene with flexible 1,7‐octadiene crosslinks in acrylic acid resins—effects on kinetics of swelling and loading of heavy metal ions from water

“…The value of the diffusion exponent ( n ) is greater than 0.50 in the case of all resins synthesized in this study. So, the diffusion is non‐Fickian, where diffusion and relaxation are said to be isochronally effective . It is explained as a consequence of slow relaxation of the polymer matrix …”

Swelling behavior and diffusion studies of high‐water‐retaining acrylamide/potassium methacrylate hydrogels

“…A fundamental and well‐accepted property of hydrogels, or SAPs, is their swelling behavior in aqueous, salt, and water‐soluble organic solutions 4–15. The swelling measurements are the main characteristic parameters for any hydrogel.…”

“…Table II shows that higher S % values were obtained when the KMA content was increased in the copolymeric chains. The increment in S % values was due to the more hydrophilic nature of the incorporated chemical groups (COO − K + ) 4–15. This was due to induction of electrostatic repulsion forces of the ionic charges of networks 4–15…”

“…The swelling kinetics of the copolymers varied as the nature of the chemical groups (e.g., hydroxyl, carboxyl, carbonyl, amide, and amine) changed in the AAm copolymer chains. This was mainly due to the many types of polymer–solvent interactions 4–8, 35, 36, 57 . r i , k S , and the theoretical equilibrium swelling ( S eq ) values of the hydrogels were calculated from the slope and intersection of the lines, as shown in Figure 6.…”