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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.

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Scanning Electron Microscopy (SEM) has been applied to the morphological study of various microcapsule systems. In addition to using standard preparation techniques for the examination of the outer structure of microcapsules, a new embedding and microtoming technique has been developed to allow the study of the inner structure of fractured capsules. The technique uses a new nonpolar embedding resin, Lowicryl HM-20, which is compatible with the microcapsule shell material, and does not introduce artifacts associated with the use of epoxy resins. We demonstrate the potential of SEM techniques as a tool for selection of wall materials, for the study of core materials distribution in microcapsules, and for elucidating the mechanisms of capsule formation and the effects of water-vapor uptake on microcapsule properties.

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