One type of hydrogel can be fabricated using end-functionalized poly(ethylene) glycol where the reactive endgroups are each difunctional (i.e. each end wants to bond to two other molecules). Consider a 1 gram sample of fully dry PEG hydrogel.
A. Sketch the conformations of some representative number of molecules illustrating how they are crosslinked.
B. Assuming the gel swells by 30 volume % after equilibration in water, modify the sketch in (a) to reflect the change in molecular structure upon hydration.
C. The swollen gel contains about 300 mg of water. To dry the gel takes about ten times as long as the time an isolated 300 mg drop of water takes to evaporate. Briefly justify why water evaporation from the gel is slower.