Influence of the Structure of Block Copolymer Nanoparticles on the Growth of Calcium Carbonate

Block copolymer nanoparticles are versatile crystal growth additives that can be used to both modify crystal morphologies and introduce new properties through their occlusion within the crystal lattice. However, the structural features that make these nanoparticles such effective additives are as yet unclear. This study employs a series of copolymer nanoparticles comprising hydrophobic cores and coronas of carboxylate and hydroxyl polymer chains to establish the design rules that govern the activity of the nanoparticles. Systematic variation of the chemical composition of the nanoparticle coronas and the length of the chains enabled us to explore two closely-linked phenomena: crystal habit modification and nanoparticle occlusion within the crystal lattice. We show that nanoparticle activity does not scale directly with carboxylate content and that nanoparticles comprising 50% carboxylate/ 50% hydroxyl groups were incorporated more effectively than those comprising 100% carboxylate chains. The accessibility of the carboxyl groups is also important, and activity is reduced when the carboxylate groups are embedded within the corona rather than being located on the particle surface. Finally, we demonstrate that occlusion and changes in crystal habit/ morphology can occur independently. These results offer a new framework for designing nanoparticles as crystal growth additives, where this provides a novel strategy for preparing inorganic nanocomposites.