Size Dispersion of the Filler Particles and Its Consequences on the Light-Extinction Properties of TiO2/PET Nanocomposite Fibers

Titanium dioxide (TiO2) nanoparticles havebeen extensivelyused to modify the optical properties of various types of materials.In particular, they have been intensively loaded onto polymer fibersto quench the light reflection. In situ polymerization and onlineaddition are two common strategies for fabricating TiO2-loaded polymer nanocomposite fibers. The former does not requireseparate preparation of masterbatches as the latter does and thereforehas its advantages in terms of decreasing the fabrication steps andeconomic costs. Moreover, it has been found that in situ-polymerizedTiO(2)-loaded polymer nanocomposite fibers (e.g., TiO2/poly(ethylene terephthalate) fibers) usually have enhancedlight-extinction properties over those prepared by the online additionprocess. Intuitively, there should be a difference in the filler particledispersion for the two fabrication processes. This hypothesis hasnot yet been tackled due to the technical difficulty in acquiringthe three-dimensional (3D) filler morphology inside the fiber matrix.In this paper, we report a study using the powerful focused ion beam-scanningelectron microscopy (FIB-SEM) with a resolution of 20 nm to directlyacquire the 3D microstructure of TiO2/poly(ethylene terephthalate)nanocomposite (TiO2/PET) fibers. This microscopy techniqueallows us to characterize the particle size statistics and the dispersioninside TiO2/PET fibers. We have found that the particlesize of TiO2 inside the fiber matrix can be well modeledby Weibull statistics. Surprisingly, we find that TiO2 nanoparticlesform more significant agglomeration in the in situ-polymerized TiO2/PET fibers. This observation is contrary to our common understandingof the two fabrication processes. Namely, slightly altering the particledispersion with increased TiO2 filler size helps improvethe light-extinction properties. The slightly increased filler sizemay have altered the Mie scattering between the nanoparticles andthe incident visible light, leading to enhanced light-extinction propertiesof in situ-polymerized TiO2/PET nanocomposite fibers.

Automated summary

Titanium dioxide (TiO2) nanoparticles have been widely used to modify the optical properties of materials, especially polymer fibers, to reduce light reflection. In this study, the 3D microstructure of TiO2/poly(ethylene terephthalate) nanocomposite fibers was directly obtained using focused ion beam-scanning electron microscopy (FIB-SEM) with a resolution of 20 nm. It was found that TiO2 nanoparticles show significant agglomeration in the in situ-polymerized fibers, contrary to common understanding. The slightly increased particle size may contribute to enhanced light-extinction properties due to altered Mie scattering with incident visible light.