Preferred polymers of formula further include polymers where R is a polyalkylene oxide, i.e., R together with the oxygens to which it is attached forms {HEAD ~ a bridging polyol}, such as polytetramethylene ether, {TAIL ~ polypropylene oxide}, polyethylene oxide, other polyalkylene oxides, including polyalkylene oxides containing mixed length alkylenes 
Preferred polymers of formula further include polymers where R is a polyalkylene oxide , i.e. , R together with the oxygens to which it is attached forms { HEAD ~ a bridging polyol } , such as polytetramethylene ether , { TAIL ~ polypropylene oxide } , polyethylene oxide , other polyalkylene oxides , including polyalkylene oxides containing mixed length alkylenes
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH