sulfonated poly coated on {HEAD ~ the polymer substrate membrane} to form {TAIL ~ an ion selective membrane}, 
sulfonated poly coated on { HEAD ~ the polymer substrate membrane } to form { TAIL ~ an ion selective membrane } ,
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH