in an amount ranging from 1 to 1/2 a total number of carbon atoms present in the alkyl group or the hydrocarbon; with the proviso that if either R6 or R7 is O- then(i) the other of R6 or R7 is not O- or OH, or (ii) if the other of R6 or R7 is O- or OH, and if X is O, X is a divalent aliphatic or aromatic linking group, or p is 0, then W is not a fluorinated hydrocarbon; ##STR24## wherein R8 is OH,