We describe herein the state of the art following the last 8 years of research into aromatic polyamides, wholly aromatic polyamides or aramids. These polymers belong to the family of high performance ...materials because of their exceptional thermal and mechanical behavior. Commercially, they have been transformed into fibers mainly for production of advanced composites, paper, and cut and fire protective garments. Huge research efforts have been carried out to take advantage of the mentioned characteristics in advanced fields related to transport applications, optically active materials, electroactive materials, smart materials, or materials with even better mechanical and thermal behavior.
High-performance aromatic polyamides García, José M.; García, Félix C.; Serna, Felipe ...
Progress in polymer science,
05/2010, Letnik:
35, Številka:
5
Journal Article
Recenzirano
Wholly aromatic polyamides (aramids) are considered to be high-performance organic materials due to their outstanding thermal and mechanical resistance. Their properties arise from their aromatic ...structure and amide linkages, which result in stiff rod-like macromolecular chains that interact with each other via strong and highly directional hydrogen bonds. These bonds create effective crystalline microdomains, resulting in a high-level intermolecular packing and cohesive energy. The better known commercial aramids, poly(
p-phenylene terephthalamide) and poly(
m-phenylene isophthalamide), are used in advanced technologies and have been transformed into high-strength and flame resistant fibers and coatings, with applications in the aerospace and armament industry, bullet-proof body armor, protective clothing, sport fabrics, electrical insulation, asbestos substitutes, and industrial filters, among others. Owing to their chemical structure, they exhibit extremely high transition temperatures that lie above their decomposition temperatures, are sparingly soluble in common organic solvents and, accordingly, can only be transformed upon solution. Research efforts are therefore underway to take advantage of their properties, enhance their processability and solubility, and incorporate new chemical functionalities in the polyamide backbone or lateral structure, so that their applicability is expanded and remains on the forefront of scientific research.
Attempts to polymerize trinitrobenzene derivatives (TNB) have been fruitless so far. Accordingly, polymers containing TNB have not been exploited in spite of their envisaged potential applications. ...Here, we describe two ways for preparing polymers with TNB moieties thus overcoming the previously reported polymerization impairments. We also report on the exploitation of the materials, both obtained as tractable transparent films and coated fibers, as smart labels for the visual detection of amine vapors. More precisely, amines in the atmosphere surrounding the sensory materials diffuse into them reacting with the TNB motifs forming highly colored Meisenheimer complexes, giving rise to development of color and to the naked eye sensing phenomenon. This is the case of highly volatile amines, such as trimethylamine, produced in food spoilage, specifically in the deterioration of fish or meat, for which the color development of the smart labels can be used as a visual test for food freshness.
Is this fish fresh? Polymers containing chemically anchored trinitrobenzene motifs are exploited as colorimetric sensors for biogenic amine vapors. Tractable transparent films and coated fibers as chromogenic smart labels are reported. Therefore, the color change of these materials upon interaction/detection of volatile amines produced in food spoilage, specifically in the deterioration of fish or meat, can be used as a visual test for food freshness.
The present work describes the implementation of a prototype to characterize thermoelectric modules (TEM). The goal is to study the energy conversion by means of thermoelectric modules mounted on ...concrete structures. The proposed experimental system is used for the electrical characterization of a commercially available thermoelectric module TEC1-12710 to prove its operation while embedded in a concrete slab, typical of building constructions. In this case, the parameters that define thermal energy conversion into electrical energy are open-circuit voltage generation, loaded circuit voltage generation, and load current. A known external load is connected to the terminals of the TEM for the purpose of its electric characterization. An electrical heating element on the hot side and a thermoelectric cooler on the cold side produce a temperature difference on the concrete slab. This arrangement allows the emulation of a temperature gradient produced by sunlight over a concrete structure. The objective is to measure the resulting electrical energy produced by the combination of concrete slab and the thermoelectric module. By controlling the temperature difference between the sides of the thermoelectric module under test, it is possible to simulate the effect of the temperature gradient under different sunlight conditions. Two digital PI controllers regulate the temperature conditions, thus providing controlled conditions for the experiments.
This study reports the results of 5 years of monitoring reef fish post‐larvae using light traps in the Bay of Tamandaré, north‐east Brazil. An annotated checklist of pre‐settlement fish species, ...their frequency of occurrence and taxonomic characteristics are provided. In total, 4,422 post‐larval fishes belonging to 36 families, 56 genera and 76 species were captured. The most species‐rich families were Carangidae (7), Lutjanidae (6) and Pomacentridae (4), while the families Gerreidae (30.47%), Holocentridae (16.54%), Blenniidae (12.01%), Labrisomidae (8.36%), Lutjanidae (8.29%) and Acanthuridae (5.95%) were the most abundant. This is the first study of the taxonomic diversity and assemblage structure of settlement‐stage reef fishes in the tropical south‐west Atlantic Ocean. Although a few common species were not captured due to selectivity of light traps, the composition and taxonomic diversity of this first collection suggests that light traps are useful for studies of the early life history of a wide range of pre‐settlement reef fishes.
A fluorogenic perylenediimide‐functionalized polyacrylate capable of generating color and fluorescence changes in the presence of triacetone triperoxide TATP), an improvised explosive used in ...terrorist attacks, under solvent‐free, solid‐state conditions has been developed. The material works by accumulating volatile TATP until it reaches a threshold; therefore, triggering colorimetric and fluorescent responses.
Spontaneous glow: A fluorogenic perylenediimide‐functionalized polyacrylate is capable of generating color and fluorescence changes in the presence of triacetone triperoxide (TATP), which is an improvised explosive used in terrorist attacks, under solvent‐free, solid‐state conditions (see figure).
Marine protected areas (MPAs) are used as fisheries management and conservation tools. Well‐enforced no‐take zones allow the rebuilding of natural populations of exploited species; however, there is ...still controversy on the role of buffer zones.
The effectiveness of MPAs could be underestimated, as fish population assessments depend largely on traditional methodologies that have difficulties in detecting predatory fish because of their low abundances, their patchy distribution, and their reaction to the presence of divers.
The performance of different census methods was compared in assessing the protection benefits for large predatory fishes under different protection levels (i.e. no‐take and buffer zones) in five Mediterranean MPAs. Specifically, conventional strip transects (CSTs, 50 × 5 m2) and tracked roaming transects combined with distance sampling (TRT + DS, variable lengths) were compared, including a series of TRT‐derived estimators with variable transect lengths and fixed widths of 20, 10, and 6 m (TRT20, TRT10, and TRT6, respectively). Additionally, the effectiveness of the MPAs studied and protection levels for conserving large predatory species was evaluated.
Transects covering larger areas (i.e. TRT + DS and TRT20) allowed the detection of a greater number of species and yielded more accurate estimates of density and biomass than transects of narrower fixed widths, particularly the CSTs, which were associated with the lowest richness detection capability, accuracy, and precision. On average, both no‐take zones and buffer zones appeared effective for the conservation of predatory fishes, indicating that multiple protection areas were ecologically effective. Differences between MPAs were also observed, however, probably arising from both local environmental and management factors.
We suggest the implementation of methodologies with larger transects for the study of large predatory fish, combined with CSTs for the rest of the fish community, in order to avoid biases in predatory population assessments, which are key indicators of MPA effectiveness.
We report herein a fluorescence polymer membrane as a film-shaped solid sensory kit for the detection and quantification in water of saccharides, namely, fructose and glucose, and dopamine. The ...sensory motifs are phenylboronic acids, which are chemically incorporated in the polymer network in the radically initiated bulk polymerization process. The sensory membrane is fluorescent. The interaction of the sensory motifs with dopamine “turn-off” the fluorescence due to a dynamic quenching, while stable complexes are formed with saccharides giving rise to a fluorescence “turn-on”. The variation of the fluorescence intensity and the wavelength of the maxima permitted the titration of the species with a detection limit of 3–4 × 10–4 M. The hydrophilic membrane allowed for the detection in water in spite of the lack of solubility in this medium of the sensory phenylboronic acid derivative monomer.
The preparation of a fluorogenic sensory material for the detection of biomolecules is described. Strategic functionalisation and copolymerisation of a water insoluble organic sensory molecule with ...hydrophilic comonomers yielded a crosslinked, water-swellable, easy-to-manipulate solid system for water "dip-in" fluorogenic coenzyme A, cysteine, and glutathione detection by means of host-guest interactions. The sensory material was a membrane with gel-like behaviour, which exhibits a change in fluorescence behaviour upon swelling with a water solution of the target molecules. The membrane follows a "turn-on" pattern, which permits the titration of the abovementioned biomolecules. In this way, the water insoluble sensing motif can be exploited in aqueous media. The sensory motif within the membrane is a chemically anchored piperazinedione-derivative with a weakly bound Hg(II). The response is caused by the displacement of the cation from the membrane due to a stronger complexation with the biomolecules, thus releasing the fluorescent sensory moieties within the membrane.
We have developed a new fluorogenic polymer capable of detecting the presence of mercury contamination in fish samples. The modified polymer emits blue light when irradiated with UV light ...proportional to the quantity of mercury, as MeHg
or Hg
, present in fish. The quantitative relation between the concentration of mercury in fish and the increase of fluorescence in the polymer in contact with fish samples was confirmed, giving rise to quick and reliable results in the measurements of the presence of mercury in fish using a portable fluorogenic polymeric probe.
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