. . . "Symmetric disulfides may be prepared conventionally by oxidizing an ?? amino-functionalized thiol like HS???(CH2)a???OCH2CH2)b???NH2, wherein a and b each independently may vary widely, e.g. from 0 to 24 (but a or b can not both be 0) or higher homologs thereof (but wherein a is preferable 6-24 and b is preferably 1-10) to form a disulfide and then reacting the amine group with a compound having a" . .