DLS-DiffusionCoefficient_Fig5.csv from Refractive index matched, nearly hard polymer colloids

Refractive index matched particles serve as essential model systems for colloid scientists, providing <i>nearly</i> hard spheres to explore structure and dynamics. The PMMA latexes typically used are often refractive index matched by dispersing them in a binary solvent mixture, but this can lead to undesirable changes, such as particle charging or swelling. To avoid this shortcoming, we have synthesized refractive index matched colloids using polymerization-induced self-assembly (PISA) rather than as polymer latexes. The crucial difference is that these diblock copolymer nanoparticles consist of a <i>single core-forming</i> polymer in a <i>single</i> non-ionizable solvent. The diblock copolymer chosen was poly(stearyl methacrylate)–poly(2,2,2-trifluoroethyl methacrylate) (PSMA–PTFEMA), which self-assembles to form PTFEMA core spheres in <i>n</i>-alkanes. By monitoring scattered light intensity, <i>n</i>-tetradecane was found to be the optimal solvent for matching the refractive index of such nanoparticles. As expected for PISA syntheses, the diameter of the colloids can be controlled by varying the PTFEMA degree of polymerization. Concentrated dispersions were prepared, and the diffusion of the PSMA–PTFEMA nanoparticles as a function of volume fraction was measured. These diblock copolymer nanoparticles are a promising new system of transparent spheres for future colloidal studies.