Size-Resolved Surface Charge Analysis of Polymer Nanoparticles: From Fundamental Measurement to Collaborative Innovation
Polymer nanoparticles (PNPs) play an increasingly central role in contemporary materials science, with applications ranging from advanced coatings and paints to biomedical drug delivery systems. Their functional performance is governed not only by particle size, but also by surface charge density (SCD), a key parameter that determines colloidal stability, interparticle interactions, and adhesion to interfaces. Despite its importance, SCD has traditionally been assessed only as a global, averaged value, obscuring the intrinsic heterogeneity that arises during nanoparticle synthesis.
Recent analytical advances now make it possible to resolve this complexity. A notable example is the work by Kruijswijk and colleagues, who developed a capillary zone electrophoresis (CZE)-based methodology to determine particle size–resolved SCD distributions of polymer nanoparticles. Their approach provides a more nuanced understanding of nanoparticle surface chemistry and opens new opportunities for rational material design.
Moving Beyond Average Values
Conventional techniques for nanoparticle charge characterization typically report a single zeta potential value for an entire population. While useful, such measurements implicitly assume homogeneity and therefore overlook variations that may critically affect performance. In reality, polymer nanoparticles often exhibit broad distributions in both particle size and surface charge, reflecting the stochastic nature of polymerization processes and surfactant interactions.
The method introduced by Kruijswijk et al. addresses this limitation by combining CZE with theoretical electrophoretic models and chemometric deconvolution. By carefully separating the contributions of particle size distribution and intrinsic charge heterogeneity to electrophoretic peak broadening, the authors demonstrate that it is possible to extract detailed SCD distributions for industrially relevant polymer nanoparticles.
This approach was validated using polystyrene nanoparticle standards and subsequently applied to poly(methyl methacrylate–methacrylic acid) and polyurethane nanoparticles with varying monomer compositions. The results clearly showed that surface charge density is not only composition-dependent but also size-dependent, with smaller particles often exhibiting higher mean SCD values. Such insights cannot be obtained from bulk measurements alone.
Implications for Industrial and Applied Research
The ability to determine size-resolved SCD distributions has important implications across multiple application domains. In coatings and paints, for example, subtle differences in nanoparticle charge can influence dispersion stability, film formation, and substrate adhesion. In biomedical contexts, surface charge plays a critical role in cellular uptake, biodistribution, and protein adsorption.
Equally important is the observation that adsorbed ions and surfactants can significantly distort apparent surface charge. By introducing a neutral surfactant to displace adsorbed ionic species, the authors were able to distinguish intrinsic polymer charge from extrinsic effects. This highlights the necessity of carefully controlled analytical environments when translating laboratory measurements to real-world formulations.
Overall, the study illustrates how advanced separation science can provide actionable knowledge for materials engineering, enabling the optimization of nanoparticle systems based on their true physicochemical properties rather than averaged proxies.
Collaboration as a Prerequisite for Impact
Research of this nature sits at the intersection of analytical chemistry, polymer science, data analysis, and industrial application. Successfully translating such methodologies from the laboratory into industrial practice requires more than technical excellence; it demands structured collaboration between disciplines and sectors.
This is precisely where IDEAS plays a crucial role. As a collaborative company and innovation environment, IDEAS provides a platform where academic researchers, industrial partners, and analytical experts can work together on complex projects such as advanced nanoparticle characterization. By fostering shared access to expertise, instrumentation, and data-driven methodologies, IDEAS enables the co-development of analytical solutions that are both scientifically rigorous and industrially relevant.
Within such a collaborative setting, techniques like size-resolved SCD analysis can be further refined, validated across different material classes, and integrated into quality control or product development workflows. Moreover, IDEAS offers a context in which fundamental research questions, such as charge heterogeneity and surface chemistry, can be directly linked to application-driven challenges faced by industry.
Towards Data-Informed Materials Design
The work discussed here exemplifies a broader shift towards data-rich, distribution-aware characterization of functional materials. Rather than relying on single-value descriptors, researchers and engineers are increasingly equipped to consider the full complexity of nanoparticle populations.
By combining advanced analytical techniques with collaborative innovation frameworks such as those provided by IDEAS, this knowledge can be translated into smarter materials, more robust processes, and ultimately more sustainable and high-performance products. For initiatives like CAST Amsterdam, such developments underscore the value of connecting fundamental science with collaborative infrastructures that support real-world impact.
Citation
Citation
Jordy D. Kruijswijk 1, Tijmen S. Bos 1, Billy van Zanten, Ton Brooijmans, Ron A.H. Peters, Kevin Jooß, and Govert W. Somsen.(2025). Assessment of Particle Size-Resolved Surface-Charge Density Distributions of Polymer Nanoparticles by Capillary Zone Electrophoresis. Analytical Chemistry, https://doi.org/10.1021/acs.analchem.5c05189
1 = Equal contributions
