Oriented Nanocomposites of Ultrahigh-Molecular-Weight Polyethylene and Gold

Melt Elongation of Polymer Nanocomposites: A Method for the Controlled Production of Dichroic Films

“…Isosbestic points were also observed in dichroic nanocomposites prepared by solid-state drawing. [10,11,16,17] However, in the case of melt processing the positions of the isosbestic points and of the absorbance maxima were much better reproducible than in the case of solid-state drawing. Interestingly, there was no essential influence of the occurring stress during melt elongation to the characteristics of the optical spectra (in particular the absorbance maxima and isosbestic points), although the stresses at 110 8C were about up to six times higher than the ones at 140 8C.…”

“…There was evidence from transmission electron microscopy (TEM) that the dichroism in solid-state drawn nanocomposites of high density polyethylene and dodecanethiol-capped gold particles stretched by solidstate drawing originated from deformation of loosely bound assemblies of gold particles from an original spherical to an elongated shape by the elongational forces during drawing. [10,11] In this case, oriented aggregates of gold nanoparticles were also indicated by scanning electron microscopy (SEM). [32] Accordingly, it was surmised that higher stresses acting during melt elongation with the RME might lead to elongated particle assemblies with a higher aspect ratio, which would lead to different UV-Vis spectra associated with different colors.…”

“…[5,6] With respect to the latter, melt processing might find notable attention because of its associated shear and extensional flows which could lead to an alignment of microscopic structures comprising nanoparticles. It has been shown that such an arrangement of particles is reflected by a dichroism, [7][8][9][10][11][12] i.e., upon observation in polarized light the color and the optical absorption spectrum depends on the angle between the polarization plane of the incident light and the orientation direction of the particle assemblies. This effect allows to generate multiple colors in a single material.…”

“…This effect allows to generate multiple colors in a single material. [8][9][10][11][12][13][14][15][16][17] Accordingly, corresponding nanocomposites act as color-polarizing filters, e.g., for use in liquid-crystal displays (LCDs). [8][9][10] Dichroic nanocomposites were already prepared toward the end of the 19th century by reduction of metal salts in natural polymer fibers that contain uniaxially oriented elongated hollow spaces in which metal particles formed in situ.…”

“…[13][14][15] More recently, dichroic nanocomposites were generated by solid-state drawing of isotropic polymermetal nanocomposites at elevated temperature, whereat gold or silver particles coated with a monolayer of organic sulfur compounds were commonly applied. [8][9][10][11][12]17] The dichroism was established by the formation of uniaxially oriented linear particle assemblies that were generated during drawing, as evident from transmission electron micrographs. Although solid-state drawing readily resulted in A processing method based on stretching of molten polymer nanocomposites was applied to prepare dichroic films.…”