Electronic speckle pattern interferometry (ESPI) was proposed to study the polymerization kinetics of hydrogels in water. The potentials of the technique were demonstrated by studying the asymmetrical hydrogel formation between a hydrophobic template and a hydrophilic template. By ESPI, the spatial distribution of gelation was successfully followed in real time, and the concentration distribution of polymer gel was evaluated. By use of this technique, it was for the first time found that the gelation was suppressed at the hydrophobic surface and resulted in an inhomogeneous distribution of the polymer network density between two templates.

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Responsiveness of a poly(acrylamide) (PAAm) hydrogel having a semi‐interpenetrating polymer network (semi‐IPN) structure was compared with that of a PAAm normal‐type hydrogel in acetone/water mixtures. The PAAm semi‐IPN hydrogel shrank much more rapidly by changes in the acetone concentration than the PAAm normal‐type hydrogel though there was no difference in their equilibrium swelling ratio between them. This suggests that the introduction of a semi‐IPN structure into a hydrogel enhances its responsiveness very easily. Copyright © 2006 John Wiley & Sons, Ltd.