Figure 2.

Generalized structural motif representing how some engineered polymeric hydrogels respond to temperature shifts as judged by water exclusion. The fluidity of hydrogels is governed by weak electrostatic interactions between water and the polymers comprising the gel. When temperature reaches a “gel” threshold, water and polymer order undergoes formidable structural rearrangements. This behavior is parallel to the thresholds observed where pure substances experience conventional phase changes.