The dynamic control over materials shape plays a key role in the complex biological environment and has attracted considerable attention in science, engineering, and medicine. We report on a novel type of dynamic shape responses exhibited by cubical hydrogel microcapsules. The capsules are produced as poly(methacrylic acid)-based hydrogel (PMAA) replicas of cubical sacrificial templates and obtained from chemically cross-linked multilayers of hydrogen-bonded precursor films.  While cubical (PMAA)20 capsules turned into spherical-like when transitioned from acidic to basic pH values, PMAA-poly(vinylpyrrolidone) capsules retained their cubical shape and increased in size instead.  The drastic difference in pH-triggered shape responses was rationalized through the difference in hydrogel rigidity expressed as the ratio of the polymer contour length between the neighboring cross-links to persistence polymer length.  We believe that our findings provide new prospects for developing polymeric materials with predictable shape and size-changing properties for controlled drug delivery and cellular uptake.

Stimuli-triggered shape responses of cubical layer-by-layer assembled hydrogel microcapsules

246th National Meeting (2013)

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