Characterization of inhomogeneous polyacrylamide hydrogels

Abstract

The physical and structural properties of acrylamide gels have been characterized by osmotic deswelling, mechanical compression, and x‐ray scattering. These properties vary considerably with the concentration of the crosslinking agent bisacrylamide, at fixed total monomers concentration (10% wt/wt water). In particular, changes in the properties appear more prominent at a crosslinking level of about 5‐6% (wt bisacrylamide/wt monomers). The compression modulus of as‐prepared and swollen gels passes through a maximum at this level of crosslinking. The swelling pressure curves can be separated into osmotic and elastic contributions of the gel network. The elastic part exhibits similar behavior to the compression modulus. The scaling of the osmotic part with the gel concentration varies with the degree of crosslinking, changing from 2.33 to 3.09. This indicates that the solvent power of water decreases with increasing crosslinking level, towards Φ conditions. The scattering patterns from the gels have been analyzed as arising from additive contributions from a homogeneous gel matrix, and embedded heterogeneities having a higher crosslinking density. These heterogeneities become much more prominent at the same level of crosslinking about 5‐6%. Hysteresis observed in the sorption/desorption behavior of polyacrylamide gel suggests that further irreversible structural changes may occur at water activities lower than probed by osmotic deswelling. © 1992 John Wiley & Sons, Inc.

Proton Diffusion andT1Relaxation in Polyacrylamide Gels: A Unified Approach Using Volume Averaging

“…Deviations from the ideal gel lead to clustering and clumping of microscopic regions of the less water-soluble bisacrylamide. Further support for the existence of microscopic (i.e., on the nanometer length scale) heterogeneities within polyacrylamide gels has been provided by light scattering studies (3,5,6). These studies indicate the existence of heterogeneous domains whose sizes vary with the amount of crosslinker.…”

“…These studies indicate the existence of heterogeneous domains whose sizes vary with the amount of crosslinker. As the crosslinker concentration increases, the scattering results have been interpreted as either the development of increasingly thicker fiber strands of acrylamide (5) or as increasing-diameter globular regions of less water-soluble bisacrylamide (3). The exact nature of these structures and the effects of crosslinker concentration on these structures have not been fully confirmed.…”

“…In addition, hydrogels have potential as experimental models of biological tissue. Hydrogel structures in general have been analyzed by a number of methods including dynamic light scattering (1-3), electron microscopy, laser light scattering (4), small angle X-ray scattering (3,5), osmotic swelling (6 -8), atomic force microscopy (9), NMR imaging (10), NMR T 1 and T 2 relaxation methods (11)(12)(13)(14), and magnetization transfer methods (15)(16)(17). Despite the wide range and number of these studies, there remain some very important unresolved issues concerning the structure of these gels and the relationships between gel structure and diffusive transport within the gel.…”

Nonergodic Dynamics of a Novel Thermally Sensitive Hybrid Gel

“…The inhomogeneous static part represents a frozen structure, while the dynamic fluctuation presumably reflects diffusive relaxation. [6][7][8][9][10][11][12][13] The concept of the nonergodicity, stated by Pusey and Van Megen, 14 has led to the development of several relevant methods to analyze dynamic properties of gels. [15][16][17] To have a better understanding of the structure and the sol-gel transition of physical gels, we have developed a novel hydrogel, in which billions of small spherical swollen poly(N-isopropylacrylamide) (PNIPAM) microgels (∼100 nm) in a concentrated dispersion are jampacked into a macroscopic three-dimensional gel network.…”

One pot synthesis and characterization of industrially important graft copolymer (GOH-g-ACM) by using peroxymonosulphate/ mercaptosuccinic acid redox pair

“…Furthermore, the graft copolymers of acrylamide on different types of cellulose [8] revealed that various properties viz flocculation, solubility, thermal stability, binding strength, water retention and drag reduction effectiveness of the substrate increases. Besides these applications poly(acrylamide) has other multiple applications viz as polymer gel dosimeter [9], for water retention: owing to its high swelling capacity [10], in electrophoresis for separation of protein and DNA samples, as a model for drug delivery systems: for studying controlled drug release profiles [11][12][13].…”