Abstract
Hydrogels containing both carboxyl and hydroxyl functional groups have been prepared by γ-irradiation of either aqueous solutions of acrylic acid (AA) and mixtures of AA and 2-hydroxyethyl methacrylate (HEMA) in different ratios, or aqueous solutions of poly(AA), PAA, and poly(AA-co-HEMA) obtained via solution polymerization. A higher absorbed dose is required in order to prepare hydrogels from monomer solutions, compared with those from polymer solutions. The range for the absorbed doses was chosen so that the probability of crosslinking reactions is higher than that of degradation ones. As the radiation energy deposited in a sample increases, the equilibrium swelling degree and the average molar mass between crosslinks diminishes. Chemical transformations induced by radiation were investigated by means of FTIR spectroscopy and thermal analysis of polymers before and after irradiation. For all these systems, the formation of a three-dimensional network enhances the glass transition temperature and thermal stability, but a further increase in the crosslinking degree may have the reverse effect on the glass transition temperature. Depending on the preparation protocol and/or hydrogel composition, superabsorbent materials that can bind different compounds throughout side functional groups may be obtained.
Highlights
Hydrogels are three-dimensional networks of hydrophilic polymers capable of absorbing important quantities of water
In this paper we focused on preparing copolymers of acrylic acid and 2-hydroxyethyl methacrylate via solution polymerization and subsequently crosslinked them by γ irradiation to produce functional hydrogels with adjustable loading capacity
Excepting the equilibrium swelling investigations, where relative standard deviation (RSD) was less than 15%, all the other above-mentioned determinations led to experimental data with RSD values lower than 2%
Summary
Hydrogels are three-dimensional networks of hydrophilic polymers capable of absorbing important quantities of water. Starting from commercially available products such as diapers or contact lenses, due to their unique physical properties, hydrogels rapidly emerge into fields like tissue engineering [1,2,3,4,5], or other biomedical applications, including drug-delivery [6,7], and in the field of detectors, actuators, etc., [8,9,10,11,12,13]. In this paper we focused on preparing copolymers of acrylic acid and 2-hydroxyethyl methacrylate via solution polymerization and subsequently crosslinked them by γ irradiation to produce functional hydrogels with adjustable loading capacity. The presence of both carboxyl and hydroxyl groups in the same macromolecular chain favors intermolecular interactions leading to more thermally stable compounds compared to the corresponding homopolymers. Depending on the preparation protocol and/or hydrogel composition superabsorbent materials that can bind different compounds throughout side functional groups may be obtained
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