BACKGROUNDAnion exchange resins are used extensively for the purification of acidic proteins. Grafting charged polymers to a rigid porous structure has been shown to improve performance under varying conditions. Understanding the underlying mechanisms is important for the optimum design and selection of material properties and operating conditions. RESULTSPositively charged grafted polymers incorporated into a rigid, porous polymeric backbone structure are found to significantly enhance adsorption capacity and kinetics of the proteins bovine serum albumin (BSA, M-r approximate to 65kDa) and thyroglobulin (Tg, M-r approximate to 660kDa) but under different conditions. For the smaller BSA, binding increases with grafted polymer length and content and decreases with salt concentration. For the much larger Tg, binding increases with the addition of some salt for the polymer-grafted resins but can be lower than that observed for ungrafted resins without added salt. This behavior is caused by diffusional hindrance due to the bound protein. Increasing the length of the grafted polymer or the pore size of the backbone improves the Tg adsorption kinetics. CONCLUSIONProtein adsorption is controlled by different mechanisms dependent on polymer grafting, backbone structure, and size of the adsorbed protein. Optimum selection of resin properties and conditions is needed to maximize adsorption capacity and mass transfer kinetics. (c) 2017 Society of Chemical Industry