Dispersion of gold nanoparticles above the poly(methyl methacrylate) surface by the use of fluoroalkyl end-capped oligomeric aggregates

Nanometer size-controlled gold particles were prepared under mild conditions by reducing the corresponding metal precursor in the presence of self-assembled molecular aggregates formed by fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers. The stable gold nanoparticles protected by these fluorinated molecular aggregates were applied to the dispersion above the poly(methyl methacrylate) film surface.     

PREPARATION OF CAULIFLOWER-LIKE PMMA PARTICLES AND THEIR FORMATION MECHANISM

A simple technique for preparing cauliflower-like PMMA particles by a self-formation method is proposed.PMMA particles can be obtained with tunable surface morphology by varying the polymerization time. Experimental results show that the formation of these cauliflower-like particles can be attributed to the special particle growth mechanism in the self-formation method.     

Two-sided ignition of a thin PMMA sheet in microgravity

Numerical computations and a series of experiments were conducted in microgravity to study the ignition characteristics of a thin polymethylmethacrylate (PMMA) sheet (thicknesses of 0.2 and 0.4 mm) using a CO₂ laser as an external radiant source. Two separate ignition events were observed, including ignition over the irradiated surface (frontside ignition), and ignition, after some delay, over the backside surface (backside ignition). The backside ignition was achieved in two different modes. In the first mode, after the laser was turned off, the flame shrank and stabilized closer to the fuel surface. This allowed the flame to travel from the frontside to the backside through the small, open hole generated by the laser’s vaporization of PMMA. In the second mode, backside ignition was achieved during the laser irradiation. The numerical calculation simulating this second process predicts fresh oxygen supply flows from the backside gas phase to the frontside gas phase through the open hole, which mixes with accumulated hot MMA fuel vapor which is ignited as a second flame in the frontside gas phase above the hole. Then, the flame initiated from the second ignition travels through the hole to ignite the accumulated flammable mixture in the backside gas phase near the hole, attaining backside ignition. The first backside ignition mode was observed in 21% oxygen and the second backside ignition mode in 35%. The duration of the laser irradiation appears to have important effects on the onset of backside ignition. For example, in 21% oxygen, the backside ignition was attained after a 3 s laser duration but was not observed after a 6 s laser duration (within the available test time of 10 s). Longer laser duration might prevent two-sided ignition in low oxygen concentrations.     

Ion irradiation of poly(methyl methacrylate) for precise control of electrical and optical properties

Ion irradiation with Xe+ has been utilized to produce electrical conductivity in PMMA, as measured using a four-point in-line probe. Incident ion beam energy and current density have been varied to investigate their effect on electrical conductivity and optical absorbance of the samples after irradiation. Results support the premise that selection of beam parameters that maximize the ratio of energy transfer-producing displacements to energy transfer-producing ionization maximizes the ratio of induced conductivity to induced absorbance in the irradiated samples. Conductivity versus ion dose has also been shown to be well estimated using a damage trial model. © 1994 John Wiley & Sons, Inc.     

Fibre optic target reflectivity sensor

This paper reports the principle of operation, the design aspects, experimentation and performance of a fibre optic target reflectivity sensor to examine the correlation between the detector output, variation in material type and the reflectivity properties of the materials tested. The device consists of a fibre optic transmitter, a fibre optic probe, target and a photodiode detector. The fibre optic probe consists of two well-polished PMMA (polymethyl methacrylate) fibres cemented together along some distance over the length. The principle of fibre optic lever displacement sensors is applied. Material effects are examined by preparing a variety of samples namely gold coated mirror, copper, brass, aluminium, steel and galvanized iron using the same polishing techniques. It is found that the response of the sensor changes with change of target surface. The results show that the fibre optic probe is capable of discriminating between materials. With the use of commercially available fibre, source and detector, the set-up proves to be simple, highly sensitive, low cost and versatile one, which can be adopted for on-line measurement or inspection of test components.     

Chemically selective soft X‐ray patterning of polymers

The chemically selective modification of polymer mixtures by monochromated soft X‐rays has been explored using the high‐brightness fine‐focused 50 nm beam of a scanning transmission X‐ray microscope. Four different polymer systems were examined: a polymethylmethacrylate (PMMA) polyacrylonitrile (PAN) bilayer film; a PMMA‐blend‐PAN microphase‐separated film; a poly(MMA‐co‐AN) copolymer film; and a poly(ethyl cyanoacrylate) homopolymer film. A high level of chemically selective modification was achieved for the PMMA/PAN bilayer; in particular, irradiation at 288.45 eV selectively removed the carbonyl group from PMMA while irradiation at 286.80 eV selectively reduced the nitrile group of PAN, even when these irradiations were carried out at the same (x,y) position of the sample. In the last two homogenous polymer systems, similar amounts of damage to the nitrile and carbonyl groups occurred during irradiation at either 286.80 or 288.45 eV. This is attributed to damage transfer between the C[triple‐bond]N and C=O groups mediated by primary electrons, secondary electrons or radical/ionic processes, aided by their close spatial proximity. Although the overall thickness of the bilayer sample at 70 nm is smaller than the lateral line spreading of 100 nm, the interface between the layers appears to effectively block the transport of energy, and hence damage, between the two layers. The origins of the line spreading in homogeneous phases and possible origins of the damage blocking effect of the interface are discussed. To demonstrate chemically selective patterning, high‐resolution multi‐wavelength patterns were created in the PMMA/PAN bilayer system.     

Selective Hg2+ sensor performance based various carbon‐nanofillers into CuO‐PMMA nanocomposites

Ternary nanocomposites (NCs) containing copper oxide (CuO)/poly(methyl methacrylate)/various carbon‐based nanofillers have been successfully prepared as thin films by an ex situ method as a selective Hg⁺² sensor. The structural, morphological, and electrochemical properties of the NCs were identified by all common characterization tools. The FT‐IR curves of these NCs proved the efficiency of CuO mixed with single‐walled CNTs (CuO/SWCNTs), multi‐walled CNTs (CuO/MWCNTs), or graphene (CuO/G) nanoparticles in the PMMA polymer matrix. The mixed nanofillers significantly improved the properties of the PMMA film. The thermal characteristics of the pure PMMA polymer matrix were highly developed by adding nanofillers in the form of NCs. The maximum composite degradation temperature (CDT_max) values were comparable for all the NCs and were in the range of 345 to 406°C. For fabrication, the CuO‐PMMA‐SWCNT, CuO‐PMMA‐MWCNT, and CuO‐PMMA‐GNCs were coated onto a glassy carbon electrode (GCE) to form a tiny layer with orderly thickness using a conductive 5% Nafion chemical binder. During the electrochemical investigation, it was found that CuO‐PMMA‐SWCNT had the maximum response toward Hg²⁺ ions compared to the other nanofillers in a buffer medium (phosphate type). To calibrate the Hg²⁺ ionic sensor, the data were plotted against Hg²⁺ ion concentration and the proposed sensor showed linearity over a wide range of concentrations (0.1‐0.01 mM), which is called the linear dynamic range (LDR). The analytical parameters, such as sensitivity (1.70 × 102 μAμM^‐1 cm^?2), detection limit (55.76 ± 2.79 pM), and limit of quantification (185.87 pM) were calculated from the calibration curve. Moreover, it showed good reproducibility, fast response time, good linearity, large LDR, and good stability. The CuO‐PMMA‐SWCNT NC‐modified GCE offers a new route to fabricate novel heavy metal ionic sensors, which might be used in green environment and health development applications.     

Chemical modification of polymeric microchip devices

Analytical polymeric microchips in both fluidic and array formats offer short analysis times, coupling of many sample processing and chemical reaction steps on one platform with minimal sample and reagent consumption, as well as low cost, minimal fabrication times and disposability. However, the invariable bulk properties of most commercial polymers have driven researchers to develop new modification strategies. This article critically reviews the scope and development of chemical modifications of such polymeric chips since 2003. Surface modifications were based on chemical derivatization or activation of surface layers with reagent solutions, reactive gases and irradiation. Bulk modification of polymer chips used newly incorporation of monomers with selective chemical functionalities throughout the bulk polymer material and integrated the chip modification and fabrication into a single step. Such modifications hold a great promise for establishing a true ‘lab-on-chip’ as can be seen from many novel applications for modulating electroosmosis, suppressing protein adsorption in microchip capillary electrophoretic separations, extraction of analytes and for zone-specific binding of enzymes and other biomolecules.     

Effect of LiCF3SO3 on L-Chitosan/PMMA Blend Polymer Electrolytes

This paper focuses on the effect of lithium triflate (LiCF₃SO₃) on the structural and conduction properties of lauroyl (L)-chitosan/poly(metylmethacryalate) (PMMA)-based polymer electrolytes. Films of L-chitosan/PMMA blends and its complexes were prepared using a solution-casting technique. The ionic conductivity of the system was measured over a wide range of frequency between 50 Hz-1 MHz. Impedance plot for the samples demonstrates two well-defined regions. The disappearance of the high frequency semicircular region led to a conclusion that the current carriers are ions. Sample with 30 wt% of LiCF₃SO₃ showed the highest conductivity of 7.59 ± 3.64 × 10^?4 Scm^?1 at room temperature. This is consistent with the results obtained from infrared spectroscopy.     

Optimal design for extending the lifetime of thin film luminescent solar concentrators

This study is concerned with the enhancement of the molecular, weathering stability of two models of thin film luminescent solar concentrators (LSCs). Two model systems of thin film LSCs had been proposed; the first model consists of a transparent PMMA/SiO₂ nanohybrid layer coated on a coumarin doped PMMA substrate. The second model designed as the ordinary configuration in which coumarin dye is dissolved in PMMA/SiO₂ nanohybrid layer then coated on a transparent PMMA substrate. The effect of nanosilica concentration on the prepared models was studied by TEM, SEM, DSC, FT-IR, UV–vis absorption and indoor photodegradation test. The obtained results suggested the first model for a durable design of thin film LSC applications specially in hot regions.