Building and Fire Research Laboratory	Nanoscience of Polymers Topics: Atomic Force Microscopy Nanoindentation of Polymers Nanoparticle Dispersion Polymer Interphases Consortium
Nanoparticle Dispersion

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Project Summary

Semiconductor particles, such as TiO₂ and ZnO, serve a number of functions in many polymeric building materials. Traditionally, they have been used as pigments to enhance the appearance properties of polymeric products. Little regard, however, has been given to other potential benefits of these pigments, such as those related to their quantum mechanical properties. For example, recent research on TiO₂ films has revealed photocatalytic activity under ultraviolet (UV) irradiation that can be used in mineralizing chemicals and bacteria. As nanosized particles, these materials exhibit optimal UV absorption, a benefit that currently has been exploited only in sunscreen applications. Also, these nanoparticles would likely enhance the stiffness and toughness of polymeric materials, for example, in applications in which mar resistance is important. Thus, because their sizes are below the wavelength of visible light, semiconductor nanoparticles could be used to optimize the durability of polymeric building materials and provide potential environmental benefits without affecting a product’s appearance.

Realization of these benefits will require significant advances in associated methods and metrologies for dispersing pigments, characterizing dispersion, and measuring mechanical properties at the nanoscale. Two of the major technical barriers involve particle dispersion techniques and measurement. Even for larger particles, dispersion remains a semi-empirical practice because of the lack of accurate and efficient non-destructive methods for measuring degree of dispersion. Further, available techniques lack the required sensitivity to measure nanoparticle dispersion. In this research, dispersion techniques and measurement methods related to the use of semiconductor nanoparticles in polymeric building materials will be developed using a combination of light and neutron scattering metrologies. Because of the effects, both beneficial and detrimental, that nanoparticles can have on material performance, bulk and nanoscale testing will be used to evaluate mechanical and optical properties as a function of dispersion. For the nanoscale testing, new experimental capabilities, i.e., the nanoindenter and the optical measurements laboratory, will be utilized. TiO2 nanoparticles and an appropriate polymeric system will be obtained through interactions with industry contacts. New dispersion equipment will be acquired with which samples will be made under various controlled conditions. Finally, methods for characterizing the degree of dispersion and the resulting mechanical and optical properties will be developed, such that a basis for optimizing system performance can be formed.

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