In {TAIL ~ one aspect} of the present invention, {HEAD ~ the polymer hydrogel} is characterized by a repeating unit having the formula 
In
In { TAIL ~ one aspect } of the present invention , { HEAD ~ the polymer hydrogel } is characterized by a repeating unit having the formula
REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH