The element of claim 32, wherein said thermal solvent has the formula (II) ##STR18## wherein n is 1, 2 or 3; p is 0 to 5-n substituents, Z, where each Z consists independently of groups selected from alkyl groups of 1 to 8 carbon atoms or halogens; L is an alkyl or alkoxy group of from 1 to 6 carbon atoms or is absent; XGY is a hydrogen bond accepting group where X and Y are each independently abs