Abstract: For the first time vapour sensors were made by assembling multi-wall carbon nanotube (CNT) decorated poly(methyl methacrylate) microbeads (PMMAµB) by spray layer by layer (sLbL). This combination of materials and technique resulted in an original hierarchical architecture with a segregated network of CNT bridging PMMAµB. The chemo-resistive behaviour of these conductive polymer nanocomposite (CPC) sensors was studied in terms of sensitivity and selectivity towards standard volatile organic compounds (VOC), as well as quantitativity and reproducibility of responses Ar to methanol, water, toluene and chloroform. Results show that 3D sLbL assembly allows boosting CNT network sensitivity by a factor 2 and selectivity for methanol vapour by a factor of 5. Additionally CNT-PMMAµB sensors gave responses proportional to vapour molecules content that could easily be fitted by the Langmuir–Henry-clustering model. Such sensors are thus expected to be good candidates for implementation in electronic noses.
Abstract: In contrast to conventional hydrophobic Conductive Polymer nanoComposites (CPCs) used to design vapor sensors, which are mostly soluble in organic solvents, monodispersed acrylate copolymer latexes present the double advantage of being more sensitive and selective towards polar vapors such as water. A hierarchically structured latex based CPC film was obtained by co-dispersion of an aqueous acrylic emulsion with multiwalled carbon nanotubes (CNTs), followed by spray layer by layer (sLbL) assembly. The analysis of CPC films morphology by AFM and TEM show that a segregated network of CNT as been achieved by partial coalescence of latex nanoparticles and homogeneously assembled in 3D. Transducer sensitivity was investigated as a function of CNT content, latex glass transition temperature (Tg), organic vapor nature and vapor concentration. The source of the high sensitivity and selectivity observed for these latex-based composites towards water vapor is assumed to mainly result from ionic interaction of SDS with water molecules offering interesting perspectives of development. The different diffusion regimes through the CPC transducer are visualized, modeled and interpreted with the Langmuir–Henry-Clustering (LHC) model, showing that only water is reaching a clustering mode at high vapor concentration. Finally it is believed that the unique hierarchical architecture of BA latex–CNT sensors is responsible for their quick, stable and reproducible responses to vapors.
Abstract: Chitosan films with various compositions of silver nanoparticles were prepared by solution casting with an aqueous solution of chitosan and l-lactic acid. The chitosan/Ag nanocomposites were characterized by wide angle Xray diffraction (WAXD) and UV-vis spectroscopy. An analysis of the surface topography and size of the Ag nanoparticles (≤100 nm) were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. Thermogravimetric analysis (TGA/DTA) confirmed the increase in thermal stability with increasing Ag nanoparticle content in the nanocomposites. Dynamic thermal analysis (DMA) was used to examine the phase relaxation behavior of chitosan and its nanocomposites. The conductivity of chitosan/Ag nanocomposites was considered with respect to the frequency. Contact angle measurements were used to characterize the surface twistability, surface cleanliness, and hydrophilic/hydrophobic nature of the surface.
Abstract: The chemo-electrical properties of chitosan-carbon nanotubes (Chit-CNT) Conductive bio-Polymer nano-Composites (CPC) transducers processed by spray layer-by-layer (LbL) technique have been investigated. Results show that unlike most synthetic polymer matrices, chitosan provides the transducer with high sensitivity towards not only polar vapours like water and methanol but also to a lesser extent toluene. Quantitative responses are obtained, well fitted with the Langmuir-Henry-Clustering (LHC) model allowing to link electrical signal to vapour content. Chit-CNT transducers selectivity was also correlated with an exponential law to the inverse of Flory–Huggins interaction parameter χ12. These properties make Chit-CNT a good transducer to be implemented in an e-nose. Additionally, the observation by atomic force microscopy (AFM) of Chit-CNT morphology suggests a chemical nano-switching mechanism promoting tunnelling conduction and originating macroscopic vapour sensing.
Abstract: Abstract
The influence of carbon nanotube (CNT) grafting with poly(ε-caprolactone) (PCL) on vapour sensing properties has been investigated for a series of Conductive Polymer Composite (CPC) transducers developed by layer by layer spray from PCL–CNT solutions. Grafting of ε-caprolactone on the CNT surface through in situ ring opening polymerisation was demonstrated by nuclear magnetic resonance after solvent extraction of ungrafted chains. Atomic force microscopy observations allowed an evaluation of CNT coating and dispersion level. Chemo-electrical properties of CPC sensors exposed to different vapours: water, methanol, toluene, tetrahydrofuran and chloroform have been analysed in terms of signal sensitivity, selectivity, reproducibility and stability. An increase of sensor response amplitude was observed when using PCL grafted CNT (PCL-g-CNT) composites in formulations.
Abstract: Preparation and properties of Chitosan (CS)-clay nanocomposites grafted with polydimethyl siloxane (PDMS) with different clay ratios are herein discussed. CS is intercalated into sodium montmorrilonite and PDMS is grafted onto CS under UV irradiation. Sample films of CS intercalated into clay and grafted with PDMS were prepared by solvent casting method with varying amount of nanoclay and PDMS. They were characterized by conventional techniques such as X-ray diffractometry, fourier transform infrared spectroscopy, 13C NMR, thermo gravimetric analysis, and differential thermal analysis. Sorption behavior of samples has been followed by measuring swelling degree and issues on the interactions of biopolymers with clay are also discussed. The water absorption of composites films reduces with an increase in the amount of incorporated clay. This is due to the barrier formation in the form of cross-linking points, which prevents water permeation into CS. The amount of adsorbed water is more, when the amount of CS exceeds the amount of PDMS. This shows high water retention capacity of CS
Abstract: The copolymers of ethylene/propylene as well as their terpolymers with polar monomers were prepared by Ni-catalyst systems and their photodegradation
behavior was studied by Fourier transform infrared spectroscopy. The polar monomers used to synthesize coand terpolymers of ethylene/propylene/polar monomer were 5-hexen-1-ol, 10-undecen-1-ol, acrylamide, methylmethacrylate,
acrylonitrile, and methylvinyl ketone. The morphological changes of the irradiated samples were determined by scanning electron microscopy. The photodegradation
kinetics has also been studied. The surface damage caused by polychromatic irradiation (l ‡ 290 nm) at 55 8C in atmospheric air is presented in different micrographs. The rate of photo-oxidative degradation is very fast in terpolymers containing polar monomers as compared with copolymers and homopolymers. The morphological study of the photodegraded samples showed a very good
correlation with the photodegraded results.
Abstract: The photo-oxidation of ethylene propylene diene monomer (EPDM)/ layered double hydroxide (LDH) composites as well as EPDM/LDH with stabilizers is studied under accelerated UV irradiation (λ ≥ 290 nm) at 60°C for different time intervals. The development of functional groups during oxidation was monitored by FT-IR spectroscopy. The photodegradation of the pristine polymer and composites take place and the increase in hydroxyl and carbonyl groups with irradiation times, was estimated. EPDM filled LDH showed higher degradation rate than pristine EPDM, while in acidic medium EPDM/LDH showed almost equal degradation as in isolated conditions. These results show the advantages of LDHs as a filler as well as an acid killer. The effect of stabilizers is very less because of their concentration in comparison of LDH.
Abstract: The degradability of ethylene propylene diene monomer (EPDM) nanocomposites, prepared from organically modified montmorillonite (OMMT), is studied under accelerated UV irradiation (290 nm) for different time intervals. The development of functional groups during degradation is monitored by FT-IR spectroscopy whereas, surface changes are studied by scanning electron microscopy (SEM). The effect of clay modifier and clay concentration on the degradability are studied. The degradation of neat polymer and composites taking place traditionally and an increase in carbonyl and hydroxyl groups are observed with irradiation time. Neat EPDM is found to be less degradable than nanocomposites. Degradation products, as seen by FT-IR in nanocomposites are found to be the same as in neat polymer but are generated at a faster rate. According to the experimental results, one can define that both ammonium ion and neat montmorillonite (MMT) accelerate the photo-oxidation of EPDM.
Abstract: A polymeric hindered amine light stabilizer (HALS), where HALS moiety was attached at the terminal end of the polypropylene chain via end-functionalized
vinylidine PP through simple organic reactions, was synthesized. It comprises the synthesis of vinylidine-terminated polypropylene by using Cp2ZrCl2/MAO as catalyst
system and epoxidation of vinylidene polypropylene. The final product was synthesized by carrying out the reaction between epoxy end functionalized polypropylene and 4- amino-2,2,6,6-tetrametyl piperidine. The final product was
characterized by using 1H NMR, 13C NMR, and FT-IR spectra. Functionality was calculated by using vapor phase osmometry and 1H NMR. The solubility and diffusion coefficient of the product were calculated and also its stabilization
performance was checked. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1596–1602, 2007
