We have developed a method to make glycopolymers with mucin-like densities of glycans based on a HA backbone with pendant target glycans and a terminal anchor tag for the preparation of glycocalyx models. The modularity of glycopolymer synthesis and surface grafting enables designer glycocalyces with quantitively tunable physical and chemical properties. Such model glycocalyces enable detailed biophysical analysis of multivalent binding processes and reveal new phenomena, as demonstrated here with regard to superselective recognition of target glycans by AB5 toxins. These and many other intriguing effects of multivalent contact between glycans and biomacromolecular complexes become amenable to mechanistic study with our glycocalyx models, shedding light on the various barrier functions of the glycocalyx in health and disease. Electronic Supporting Information (ESI). Experimental procedures, QCM-D data, SE data, 1 H NMR and SEC-MALS data for polymers. The raw data associated with this paper will be made openly available from the University of Leeds data repository upon publication.