Relationship between water absorbency and reaction conditions in aqueous solution polymerization of polyacrylate superabsorbents

Abstract

Polyacrylate superabsorbents were prepared by in situ aqueous solution polymerization in a polyethylene bag, which was submerged in a water bath. The influence of the initiator content, bath temperature, isopropanol content, initial monomer concentration, and crosslinker content (Cc) on water absorbency (Q) were investigated. The temperature change of the monomer mixture during polymerization was also analyzed. Increase of the chain ends in networks resulting from decrease of the molecular weight in free-radical polymerization causes an increase of the water absorbency of superabsorbents and also reduces the crosslinking efficiency. The results are in conformity with the classical network theory. An empirical relation of Q ϭ 2.45 Cc Ϫ0.600 was obtained and the validity of Flory's swelling equation was confirmed indirectly.

Synthesis and absorbency of gelatin-graft-poly(sodium acrylate-co-acrylamide) superabsorbent hydrogel with saltand pH-responsiveness properties

“…Such a behavior is well-known as reported by pioneering scientists [2,11,28]. Chen and Zhao have also reported a similar behavior for an acrylic-based superabsorbent [29]. Higher crosslinker concentration decreases the space between the copolymer chains and, consequently, the resulted highly crosslinked rigid structure cannot be expanded and hold a large quantity of water.…”

Biosuperabsorbent Hydrogel Based on Alginate-g-poly AA/kaolin Composite for Releasing Cefalexin Drug

“…The difference in between initial drug and the drug content in the washing solutions is taken as an indication of the amount of entrapped drug: For the investigation of drug adsorption behavior of hydrogels prepared in this study, hydrogels were ûrstly swollen in cefalexin solution in concentration range 0.50-3.0 mg/mL. As can be seen from the Figure 4, an increase in drug concentration in the swelling medium increased the amount of adsorbed drug, as observed in many adsorption studies [17][18] . This result can also be obtained from the following equation:…”

“…It is obvious that with increasing the loading time, the amount of drug loaded increased and then in the beginning decreased. The initial increment in the amounts of the loaded drug with increasing loading time can be ascribed to the increased drug diffusion into the swollen matrix [18]. The most effective time of loading efficiency was 30 h, where the high amount of drug was encapsulated.…”

Synthesis, Characterization and Swelling Properties of Chitosan/Poly(acrylic acid-co-crotonic acid) Semi-Interpenetrating Polymer Networks

“…This possible phenomenon is referred to as "self crosslinking" by other workers. 41 An additional reason for decreasing the absorbency can be related to decreasing molecular weight (MW) of the copolymer at high levels of APS concentration. Since MW inversely depends on initiator concentration, [I], higher [I] results in lower MW and, in turn, lower swelling capacity of the hydrogel.…”