Polymer Nanocomposites Containing Anisotropic Metal Nanostructures as Internal Strain Indicators

Abstract

Polymer/metal nanocomposite containing intrinsically anisotropic metal nanostructures such as metal nanorods and nanowires appeared extremely more sensitive and responsive to mechanical stimuli than nanocomposites containing spherical nanoparticles. After uniaxial stretching of the supporting polymer matrix (poly(vinyl alcohol)), the elongated silver nanostructures embedded at low concentration into the polymer matrix (<1 wt % of Ag) assume the direction of the drawing, yielding materials with a strong dichroic response of the absorption behavior. Accordingly, the film changed its color when observed under linearly polarized light already at moderate drawings. The results obtained suggest that nanocomposite films have potential in applications such as color polarizing filters, radiation responsive polymeric objects and smart flexible films in packaging applications.

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

“…Films of poly(vinyl alcohol) comprising 0.8% m/m silver nanorods (width about 160 nm, aspect ratio ≥90) stabilized by adsorbed poly(vinyl pyrrolidone), prepared by solution casting, changed color from violet ( ϕ = 0°) to green ( ϕ = 90°) after drawing (draw ratio 5) . This color change was also reflected in UV–visible absorption spectra, which showed the common features of dichroic samples (shift of λ max to higher wavelengths at ϕ = 0°, isosbestic point).…”

“…51 Rod-like nanoparticles Similar to the above described nanocomposites with isotropic particles, rod-like silver nanoparticles (widths of the order of 10-40 nm, typical aspect ratios ≤5) were incorporated in poly(vinyl alcohol) after casting of polymer solutions with dispersed particles. 15,16,52 After drying, the resulting films were drawn at elevated temperature to draw ratios up to 5. 15,16 The rod-like particles oriented with the long axis preferentially parallel to the drawing direction, 15,16 and in one case it was shown by SEM that the particles formed uniaxially oriented assemblies (which also contained particles of other shapes such as spheres).…”

“…15,16,52 After drying, the resulting films were drawn at elevated temperature to draw ratios up to 5. 15,16 The rod-like particles oriented with the long axis preferentially parallel to the drawing direction, 15,16 and in one case it was shown by SEM that the particles formed uniaxially oriented assemblies (which also contained particles of other shapes such as spheres). 15 Notably, in highly viscous liquids subjected to shearing, orientation of gold nanorods (average aspect ratios 2.4-4.2) were oriented only as long as the shear forces were present; orientation was lost almost immediately when the shear rate was decreased to zero.…”

“…roughly spherical) [12][13][14]17,18,21 or rod-like nanoparticles. 6,15,16,19,20 The drawing process leads to orientation of the polymer molecules which can obviously induce concomitant formation of oriented particle assemblies or orientation of rod-like particles with the long axis parallel to the drawing direction. Shear forces acting during Walter Caseri graduated at ETH Zürich with a PhD in 1987.…”

Comparative study of nano iron catalysts in the presence of the crude polymer matrix and their cross link polymer in the Fischer-Trophsch synthesis

“…Indeed, extensive and intensive work has been done on the synthesis of polymer/nanoparticles composite materials as a catalyst, due to their direct importance reforming and cracking hydrocarbons [4] . It is therefore very important to find synthetic methodology to produce nanoparticles that have significant impact on changing of physical and chemical properties of such materials, so they should be well investigated [5][6][7][8][9] . The effect of using polymers as stabilizers in the synthesis of cobalt and iron based nanoparticles was studied by Claver [10] .…”