(340e) Decoupling Temperature and the Kinetics of Dye Conversion Via Scalable Nano-Encapsulation in a Thermal-Responsive Media

Authors: 
Scott, D., Princeton University
Feng, J., University of Illinois, Urbana-Champaign
Prud'homme, R. K., Princeton University
Priestley, R. D., Princeton University
Armstrong, M., Princeton University
Chemical treatment processes in which substrates are exposed and interact with chemicals require quality control to ensure process specifications such as temperature, dosage, and duration are satisfied. One approach for quality control is the use of colorimetric dyes which undergo chemical reactions in response to an applied treatment, thereby shifting their absorbance spectrum. When incorporated in a process run alongside samples, operators can observe these post-treatment color changes as qualitative success metrics. While this approach is simple to implement, the reliance on the kinetics of dye conversion presents challenges including dye aging during storage which can lead to false positive results as well as the inability to decouple the effects of dosage and temperature on the final result.

We seek to overcome this disadvantage by decoupling the kinetics of dye conversion from temperature through the implementation of a wax matrix surrounding dye nanocapsules. The wax matrix serves as a barrier which melts and exposes dye-encapsulated nanoparticles at a specific melting temperature, commensurate with that of the treatment process. To form dye nanocapsules directly in wax, the versatility of flash nanoprecipitation (FNP), a scalable nanoparticle fabrication technique, is expanded. In this work, an organic solution of dye and polymeric stabilizer is impinged against a molten wax to create turbulent mixing, yielding the super-saturation, precipitation, and subsequent two-level encapsulation of the dye. Characterization of the resultant nanoparticle-imbued waxes is presented as well as the response of encapsulated dye to treatments at temperatures above and below the melting point of various wax matrices. As a result, the ability of these novel materials to thermally trigger exposure and initiate the kinetic response of the dye is demonstrated. Nanoparticle-imbued waxes are shown to be amenable to further post-processing including emulsification, spray prilling, and printing.