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