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