The synthesis and systematic comparison of a comprehensive library of well-defined polymer architectures based on poly(acrylic acid) is reported. Through the development of new synthetic methodologies, linear, single branched, precision-branched comb, and star polymers were prepared and their performance as dispersants was evaluated. The ability to accurately control chain lengths and branch points allows the subtle interplay between structure and dispersant performance to be defined and affords critical insights into the design of improved polymeric additives for coating formulations. The general industrial relevance of ionic polymers and branched macromolecular architectures supports these design rules for a wide range of other applications and materials, including as additives for personal care products and in water treatment. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 716-725