We describe the synthesis of biotin end functionalized poly(sulfonic acid)s via living radical polymerization (LRP) for conjugation to Avidin. Quartz crystal microbalance (QCM-D) and competitive binding studies were used to confirm this conjugation. A biotin initiator for copper-mediated LRP was used to provide acrylamide and methacrylate based polymers with the functional end group. This investigation revealed that 2-acrylamido-2-methyl-1-propanesulfonic acid was not a suitable monomer in its acid form but was successfully used in its sodium salt form. A second monomer, 3-sulfopropylmethacrylate as the potassium salt was also studied and both monomers produced polymers with polydispersities <1.3 and 1.4, respectively. Evolution of molecular weight with respect to time indicated that the polymerization of the acrylamide polymer is controlled. Quartz crystal microbalance with dissipation monitoring was used to confirm that the biotinylated polymers were able to bind to Avidin in situ. The gold surface of a quartz crystal was chemically modified resulting in a stable monolayer of Avidin; the biotinylated polymers were passed over the functionalized surface and their grafting ability was examined. A competitive binding evaluation was undertaken with 2-(4-hydroxyphenylazo)benzoic acid (HABA) dye to provide visual verification of conjugation. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 1163-1173, 2011