Terahertz Spectroscopy of Single-Walled Carbon Nanotubes in a Polymer Film: Observation of Low-Frequency Phonons

We investigate the dielectric response of single-walled carbon nanotubes dispersed in poly(vinyl alcohol) matrix by using terahertz time domain spectroscopy. Frequency-dependent real and imaginary parts of the complex dielectric function are measured experimentally in the terahertz regime. The low-frequency phonons of carbon nanotubes, though predicted theoretically, are directly observed for the first time at frequencies 0.26, 0.60, and 0.85 THz. Further, a broad resonance is observed at 1.15 THz associated with the longitudinal acoustic mode of vibration of straight-chain segments of the long polymeric molecules in the film. The latter is observed at 1.24 THz for a pristine polymer film and has been used to derive the size of crystalline lamellae in the film.

Electron field emission from reduced graphene oxide on polymer film

Field emission of reduced graphene oxide coated on polystyrene film is studied in both parallel and perpendicular configurations. Low turn-on field of 0.6 V/lm and high emission current density of 200 mA/cm(2) are observed in perpendicular configuration (along the cross section), whereas a turn-on field of 6 V/lm and current density of 20 mu A/cm(2) are obtained in parallel configuration (top surface). The emission characteristics follow Fowler-Nordheim (FN) tunneling and the values of enhancement factor estimated from FN plots are 5818 (perpendicular) and 741 (parallel). Furthermore, stability and repeatability of the field emission characteristics in perpendicular configuration are presented. (C) 2013 American Institute of Physics. http://dx.doi.org/10.1063/1.4788738]

Polymer film packaging for food: An environmental assessment

Plastics packaging is ubiquitous in the food industry, fulfilling a range of functions including a significant role in reducing food waste. The public perception of packaging, however, is dominated by end-of-life aspects, when the packaging becomes waste often found littering urban, rural and marine environments. A balanced analysis of the role of packaging demands that the whole lifecycle is examined, looking not only at the packaging itself but also at the product being packaged. This paper focuses on packaging in the meat and cheese industry, analysing the impact of films and bags. The functions of packaging are defined and the environmental impact of delivering these functions is assessed. The influence of packaging on levels of waste and energy consumption elsewhere in the system is examined, including the contentious issue of end-of-life for packaging. Strategies for minimizing the environmental impact of the packaging itself involve reduction in the amount of material used (thinner packaging), rather than emphasizing end-of-life issues. Currently, with polymer recycling not at a high level, evidence suggests that this strategy is justifiable. Biodegradable polymers may have some potential for improving environmental performance, but are still problematic. The conclusion is that although current packaging is in some ways wasteful and inefficient, the alternatives are even less desirable. © 2013 Elsevier B.V. All rights reserved.

Determination of the absorption for incident light propagating parallel through the guest-host polymer film waveguide

Guest host polymer thin films of polymethyl methacrylate (PMMA) incorporated with (4'-nitrobenzene)-3-azo-9-ethylcarbazole (NAEC) were fabricated by spin coating and then poled by the method of corona-onset poling at elevated temperature. The absorption mechanism of the polymeric film, which is very important for the optical transmission losses and directly relates to the orientation of chromophore NAEC in polymer PMMA, was investigated in detail. From the UV-visible absorption spectra for NAEC/PMMA film before and after being poled, we determined the change of absorption coefficient kappa with the wavelength and approximately calculated the maximum absorption A(parallel tomax) as 3.46 for incident light propagating parallel through the film, i.e. the ordinary polarized light, which cannot be directly measured in the spectro photometer. (C) 2002 Elsevier Science Ltd. All rights reserved.

Cellulose acetate polymer film modified microstructured polymer optical fiber towards a nitrite optical probe

A novel microstructured polymer optical fiber (MPOF) probe for nitrites (NO(2)(-)) detection was made by forming rhodamine 6G (Rh 6G)-doped cellulose acetate (CA) on the side wall of array holes in a MPOF It was found that the MPOF probe only have a response to nitrites in a certain concentration of sulfuric acid solution The calibration graph of fluorescence intensity versus nitrites concentration was linear in the range of 2.0 x 10(-4) g/ml-5.0 x 10(-3) g/ml. The method possesses case of chemical modification, low cost design, and potential for direct integration with existing instrumentation, and has been applied to the determination of nitrites in real samples with satisfactory results. (C) 2010 Elsevier B.V. All rights reserved

Pattern formation in a confined polymer film induced by a temperature gradient

We have studied a morphological instability of a double layer comprising the polymer film and air gap confined between the two plates set to different temperatures. The temperature gradient across the double layer causes the breakup of the polymer film into well-defined columnar, striped or spiral structures spanning the two plates. The pattern formation mechanisms have been discussed. The formed patterns can be transferred to produce PDMS stamp, a key element of soft lithography for future microfabrication.

Ordered droplet formation by thin polymer film dewetting on a stripe-patterned substrate

The dewetting process of thin polystyrene (PS) film on flat and stripe-patterned substrates is presented. Different dewetting processes were observed when the thin PS films annealed at above the glass transition temperature on these different kinds of substrates. The final dewetting on the flat substrate led to formation of polygonal liquid droplets, while on the stripe-patterned substrate, the droplets were observed to align at the centers of the stripes. A possible explanation for the dewetting process on the stripe-patterned substrate is proposed.

A composite polymer film with both superhydrophobicity and superoleophilicity

A composite film composed of porous polyurethane (PU) and polystyrene (PS) microspheres with both superhydrophobicity and superoleophilicity has been prepared. In this film, the dual-scale structure enhances both the hydrophobicity and oleophilicity of the surface material. The composite film with such an 'intelligent' wettability property can be utilized to separate oil and water systems efficiently.

ELECTROACTIVE COATINGS OF DICYANO-BIS(1,10-PHENANTHROLINE)IRON(II) ATTACHED TO NAFION POLYMER FILM-MODIFIED ELECTRODES VIA ADSORPTION

A dicyano-bis(1,10-phenanthroline)iron(II) modified elecrode was prepared. The voltammetric and the spectroelectrochemical behavior of this electrode were investigated. The influence of pH and the amount of Nafion and dicyano-bis(1,10-phenanthroline) iron(II) (DBPI) used in the electrode preparation on the electrochemical behavior is presented.

AMPEROMETRIC DETECTION OF AMINO-ACIDS IN A FLOW-INJECTION SYSTEM WITH A NICKEL(II)-MODIFIED ELECTRODE WITH AN EASTMAN-AQ POLYMER FILM

Amperometic flow measurements were made at +0.55 V (vs. Ag/AgCl) in 0.1 mol l-1 KOH electrolyte with an Ni(II) chemically modified electrode (CME) with an Eastman-AQ polymer film. The use and characteristics of a Ni(II)-containing crystalline and polymer-modified electrode obtained by a double coating step as a detector for amino acids in a flow-injection system using reversed-phase liquid chromatography are described. The detection of these analytes is based on the higher oxidation state of nickel (NiOOH) controlled by the applied potential. The electroanalytical parameters and the detection current for a series of amines and amino acids were investigated. The use of such a CME in the flow-injection technique was found to be suitable in a solution at low pH. The linear range for glycine is 5 X 10(-6)-0.1 mol 1-1 with a detection limit of 1.0 X 10(-6) mol l-1. A 1 X 10(-4) mol 1-1 mixture of serine and tyrosine was also detected after separation on an Nucleosil C18 column.

STUDY ON MASS-TRANSPORT IN EASTMAN-AQ POLYMER FILM BY USING NON-STEADY-STATE CHRONOAMPEROMETRY AT AN ULTRAMICRODISK ELECTRODE

Non-steady-state chronoamperometry of ultramicroelectrodes is a powerful method for the study of mass transport in polymer films. This method has many advantages over the conventional methods at a macroelectrode and the steady state method at an ultramicroelectrode, which yield the most information. The apparent diffusion coefficient, D(app), and the concentration of reactant in the film, c(f), can be determined from a single experiment without knowing the thickness of the film. We studied the transport of several species such as Ru(NH3)63+, Ru(bpy)3(2+), NR and MV2+ in Eastman-AQ polymer film coated ultramicroelectrodes by using this method.

A NEW KIND OF ION-SELECTIVE ELECTRODE BASED ON CONDUCTING POLYMER FILM

Organic conducting polymers have attracted much interest in material science. This letter reports potentiometric response behavior of polypyrrole (PPy)polymer film electrodes prepared by electrochemical polymerization, and a new kind of ion selective