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