Whereas the structural diversity of zwitterions is a priori very high comprising a plethora of different anionic as well as cationic groups, [12] commonly used zwitterionic materials for low-fouling purposes belong to the three major families of carboxybetaine, sulfobetaine, and phosphatidylcholine containing polymers. [7,[12][13][14][15] Several studies have shown that the precise molecular structure of these polymers affects their inertness against fouling. Essential molecular parameters include not only the chemistry of both the anionic and the cationic groups, [16][17][18][19][20][21][22][23][24][25] but also the nature of the polymer backbone, [16,17,22,[26][27][28][29] the distance of the zwitterionic moieties from the backbone, [16,[30][31][32] the zwitterion's dipole orientation, [18,[33][34][35][36] and the length of the alkylene spacer between the ionic groups. [17,[37][38][39] For instance, in a set of otherwise identical polycarboxybetaines with varying inter-charge spacer, the adsorption of blood protein fibrinogen was lowest for two carbon atoms separating the ammonium and the carboxylate groups, increasing in the order 2 < 1 < 3 < 5. [40] Similarly, polycarboxybetaines with one and two carbon atoms separating the ammonium and the carboxylate groups were significantly more effective in reducing fouling by human blood