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The controlled functionalization of surfaces is of utmost importance for many applications. Surface-initiated living anionic polymerization (SI-LAP) offers a well-adjustable, uniform functionalization without the necessity of metal catalysts for polymerization. However, this technique is rarely studied for functional monomers, such as different methacrylates. The present study investigated the SI-LAP of different methacrylate monomers on porous polystyrene microparticles. Starting with methyl methacrylate (MMA) as the model monomer, the reaction kinetics and the living character of the polymerization at the particles’ surface are discussed. The reaction conditions were transferred to more functional methacrylates, for example, 2-(trimethylsilyloxy)ethyl methacrylate (HEMA-TMS). The functionalization in the particle’s interior enables the preparation of fluorescent particles by applying post-modification protocols of the poly(hydroxyethyl methacrylate) (PHEMA) moieties with fluorescein isothiocyanate. Moreover, ferrocenylmethyl methacrylate (FMMA) polymerization leads to stimuli-responsive particles with an adjustable functional polymer content of 7 to 51%. Electrochemical studies for the latter polymer poly(ferrocenylmethyl methacrylate) (PFMMA) on the surface offered remarkable long-term stability upon addressing the redox responsiveness of the ferrocene moieties over 1000 cycles using electrochemistry. The synthesis strategy enables access to various applications, such as battery anodes, redox-flow batteries, or ion sorbents.

Due to the limited available amounts of components, especially of low water-soluble drugs, formulation development is often impeded by a careful characterization. The use of small batch sizes might solve this problem but requires also adequate analytics. Concentration of nanoparticulate formulations lack straightforward evaluation techniques. In this work, a precise and straight-forward method is established to individually count nanoparticles. A microfluidic chip with known dimensions was used to visualize single particles flowing through the channel (single-particle tracking (SPT)). A sequence of 10,000 images was analyzed to determine the mean particle concentration. The proposed method is independent of the particular flow rate through the microfluidic chip as long as there is no particle overlap and a continuous exchange of particles. Monodisperse Rhodamine B labeled poly (methyl methacrylate) (PMMA) nanoparticles (267.03 ± 9.79 nm) were used as a model and reference particle system for the evaluation process of SPT allowing for a gravimetric determination based on density analysis using analytical ultracentrifugation (AUC) and gas pycnometry. The SPT method was evaluated and compared to other techniques used for concentration measurement. Both approaches (SPT and gravimetry) provide very similar and comparable results indicating the applicability of this novel quantification approach. In contrast, multi angle dynamic light scattering (MADLS) could not yield a precision as good as SPT (number density rel. standard deviation SD nSPT = 11.67%; SD nMADLS = 49.45%). Finally, the measured particle number concentrations can be realized in low concentration ranges (0.8249 μg mL−1– 0.08249 μg mL−1) not accessible for MADLS (0.08249 mg mL−1– 0.008249 mg mL−1) and gravimetric analysis.