Structure and relaxation properties of medical‐purposed polyacrylamide gels

Abstract

By IR and NMR spectroscopy methods, thermomechanical analysis, mechanical relaxation measurements, and computational simulation the effect of production conditions of acrylamide copolymer and N,NЈ-methylenebisacrylamide derived hydrogels with respect to their properties were studied. Four hydrogel samples, prepared under different production conditions (␥-radiation dose and autoclaving), were investigated. It was found that autoclaving and ␥-radiation lead to a slight increase of the crosslinking degree in the polymeric network and formation of alkene structures in polymeric chains. Stress relaxation and creep processes under axial compression of gel cylindrical samples were studied in detail. To approximate stress relaxation and creep curves new memory functions were used, based on the analysis of entropy production in the system during the relaxation process. It was found that primary ␥-radiation of initial gels induces an increase of quasi-equilibrium rubbery elasticity modulus, and quasi-equilibrium compliance is decreased. The opposite situation is observed during further autoclaving at 120°C. After autoclaving, required to sterilize the gels, their treatment by ␥-radiation again induced a noticeable increase of the modulus and compliance decrease. The mechanism of relaxation processes was found to be associated with the limiting stage of physical interaction between relaxants, representing different micro-inhomogeneities in the material. The investigation results were compared with the data obtained by histology and morphology methods. A hydrogel obtained under additional ␥-radiation treatment and autoclaving did not swell when implanted into a living organism, and the tissue reaction to implantation of such gel was minimal.

On the mechanical strength of biocompatible semi-IPNs of polyvinyl alcohol and polyacrylamide

“…Thus, realizing the vital role of PVA in biomedical engineering, the present investigation aims at preparing Semi-interpenetrating polymer networks (semi-IPNs) of PVA and crosslinked PVA to achieve strong and yet elastic hydrogel or desired mechanical property. PAM is well-known hydrophilic polymer and has been greatly used in the field of agriculture and biomedicine (Lopatin et al 2005;Durmaz and Okay 2001 …”

Radiation induced crosslinking effect on semi - interpenetrating polymer networks of poly(vinyl alcohol)

“…The use of poly(acrylamide) hydrogels in the field of agriculture [21] and biomedical [22] has been reported. Workers have synthesized polyacrylamide and gels derived from it using γ-irradiation [23]. For instance, Nizam El-Din and coworkers [24] have recently reported the use of gamma radiation in synthesis of hydrogel made up of PVA and polyacrylamide.…”

Computing thermomechanical properties of dry homopolymers used as raw materials for formulation of biomedical hydrogels

“…Nevertheless, the solubility parameter of TFEM remains the weakest value independently of the method in comparison with the other polymers. Moreover, the ranking obtained from both computed and literature values is similar polyacrylamide (30.8 MPa 0.5 [44]) > HEMA (29.6 MPa 0.5 [45]) > GMA (20.5 MPa 0.5 [32]) > TFEM (15.9 MPa 0.5 [43]). For GMA the solubility parameter was calculated using the atomic increments approach proposed by Askadskii, whereas concerning HEMA, the solubility parameter, as usually done for polymer, was matched to that of the solvent with the maximum solvating power, the methanol in this case.…”