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

Abstract

A processing method based on stretching of molten polymer nanocomposites was applied to prepare dichroic films. First, dodecanethiol‐capped gold particles were embedded in low density polyethylene. The resulting isotropic films were stretched in the melt under uniaxial loading using an elongational rheometer. The melt elongation technique resulted in reproducible characteristics of the optical properties and can be directly transferred to an industrial scale. The organic coating of the metal particles plays an important role in the generation of the dichroism. A reactive surface (adsorbed perfluorophenyl azide) led to strongly agglomerated particles which obviously did not lead to dichroic films.magnified image

Dichroic nanocomposites based on polymers and metallic particles: from biology to materials science

“…21 Figure 6. SEM image of a film comprising 2% m/m gold in polyethylene after stretching of the sample in the molten state at a temperature of 130 ∘ C. 50 The drawn materials were dichroic 15,16,52 already at a draw ratio of 1.5, 16 with UV-visible absorption spectra 15,16,52 showing the same characteristics as described above for dichroic nanocomposites with isotropic particles. When films were irradiated with a laser beam of wavelength 350 nm, the irradiated spots lost their dichroic behavior.…”

“…Besides extension of solid samples, oriented assemblies of dodecanethiol‐coated gold nanoparticles were also generated by elongation of the molten polymer matrix . This method can basically be transformed to technological procedures which involve pronounced elongational flow such as calendaring or film blowing.…”

“…SEM image of a film comprising 2% m/m gold in polyethylene after stretching of the sample in the molten state at a temperature of 130 °C …”

“…49 Besides extension of solid samples, oriented assemblies of dodecanethiol-coated gold nanoparticles were also generated by elongation of the molten polymer matrix. 50 This method can basically be transformed to technological procedures which involve pronounced elongational flow such as calendaring or film blowing. For this purpose, first toluene solutions of polyethylene containing dispersed gold nanoparticles were dried and the films thus obtained were folded and pressed at elevated temperatures.…”

Transparent polymer nanocomposites: An overview on their synthesis and advanced properties

“…This kind of composite exhibits different colors when they are illuminated by polarized light. The absorption of the visible light and the color of the composite change depending on the angle between the orientation direction of the metal particles in the composite and the polarization plane of the incident light [6,258]. To align the particles into the polymer matrix different techniques were developed such as solid-state drawing or melt elongation [2,6].…”