affinity macroligands comprising a reversibly water soluble poly - n - alkylacrylamide linked to a ligand , and their use in the separation of a target substance from a mixture comprising the target substance and other materials are disclosed . preferred amls have number average molar masses of less than 7 , 000 g / mol , mass distributions of less than 1 . 2 and narrow precipitation - solubility temperature interval , typically in the range of 1 - 2 ° c .