A family of graft copolymers that can sterically inhibit interactions between biological surfaces was developed. These copolymers contained phenylboronic acid (PBA) groups as saccharide-binding moieties on a poly-(L-lysine) backbone and poly(ethylene glycol) (PEG) grafted as adhesion-resisting side chains. These copolymers spontaneously chemisorbed to a saccharide-containing resin, and this binding was sterically controlled by the PEG grafting ratio. Copolymers with optimal grafting ratios spontaneously assembled on red blood cell surfaces and sterically prevented their agglutination by lectins and by antibodies to blood groups. The simple conjugation scheme created a PBA moiety with a pKa ca. 6, which can bind cis-diols much more strongly at physiological pH than typical PBA moieties, whose pKas are typically greater than 8. These surfactant copolymers can be employed to PEGylate cell or tissue surfaces by simply incubating the surfaces with an aqueous polymer solution, and have many potential applications such as preventing antibody binding to transplanted cells. [on SciFinder (R)]