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Polymers are extensively used in food and beverage packaging to shield against contaminants and external damage due to their barrier properties, protecting the goods inside and reducing waste. However, current trends in polymers for food, water, and beverage applications are moving forward into the design and preparation of advanced polymers, which can act as active packaging, bearing active ingredients in their formulation, or controlling the head-space composition to extend the shelf-life of the goods inside. In addition, polymers can serve as sensory polymers to detect and indicate the presence of target species, including contaminants of food quality indicators, or even to remove or separate target species for later quantification. Polymers are nowadays essential materials for both food safety and the extension of food shelf-life, which are key goals of the food industry, and the irruption of smart materials is opening new opportunities for going even further in these goals. This review describes the state of the art following the last 10 years of research within the field of food and beverage polymer's applications, covering present applications, perspectives, and concerns related to waste generation and the circular economy.

Low-density porous aramid films using inexpensive and widely available polymers as porosity promoters, that is, polyvinyl alcohol (PVA), poly(2-ethyl-2-oxazoline) (PEOx), and cellulose polyacetate (CA) were fabricated. Porous poly (m-phenylene isophthalamide) films were obtained by the standard casting procedure using mixtures of the aramid with either PVA, PEOx, or CA, followed by the removal of the porosity promoter polymers by immersing them in water or acetone. As a result, films with up to a 65% density reduction with pore sizes ranging from 0.02 to 10 μm and up to 30% increment in Young's modulus were obtained. In addition, the morphology of the films was homogeneous and was controlled by the proportion and nature of the porosity promoter polymer. The density reduction of materials plays a significant role in energy crises and the need for fuel reduction. This study revealed that it is possible to prepare low-density porous aramid films inexpensively without impairing their outstanding performance by using PVA in the casting procedure as a porosity promoter polymer., Regional Government of Castilla y León (Junta de Castilla y León), the Ministry of Science and Innovation MICIN and the European Union NextGenerationEU / PRTR, and the Spanish Agencia Estatal de Investigación (State Research Agency), Grant/Award Number: PID2019-108583RJ-I00/AEI/10.13039/501100011033

We report on the preparation, characterization, and foaming behavior of cellular polymers based on 1-vinyl-2-pyrrolidone (VP) and methyl methacrylate (MMA). Samples with different feed ratios proportions of VP and MMA were prepared following the bulk radical copolymerization procedure, using commercially available monomers and testing two different initiators (photochemical and thermal), obtaining solid samples of around 1.5 mm thick. To evaluate the polymerization process, the chemical structure of VP/MMA copolymers was determined by proton nuclear magnetic resonance measurements. In a second step, single-batch supercritical carbon dioxide (CO2) foaming tests were carried out at different temperatures to evaluate the influence of the VP to MMA feed ratios and the foaming temperature in the density, the presence of solid outer skin, the CO2 sorption–desorption process, and the cellular morphology of the foamed polymers.

We prepared high-performance aromatic copolyamides, containing bithiazole and thiazolo-thiazole groups in their main chain, from aromatic diamines and isophthaloyl chloride, to further improve the prominent thermal behavior and exceptional mechanical properties of commercial aramid fibers. The introduction of these groups leads to aramids with improved strength and moduli compared to commercial meta-oriented aromatic polyamides, together with an increase of their thermal performance. Moreover, their solubility, water uptake, and optical properties were evaluated in this work., Fondo Europeo de Desarrollo Regional and both the Spanish Ministerio de Economía, Industria y Competitividad (MAT2017-84501-R) and the Consejería de Educación, Junta de Castilla y León (BU306P18) is gratefully acknowledged. M.T.L. also thankfully acknowledges the Spanish Ministerio de Ciencia e Innovación (PID2019-108583RJ-I00/AEI/10.13039/501100011033)

We prepare low density nanoporous aramid films reinforced with carbon-based nanocharges (graphene, carbon nanofibers and carbon nanotubes), using ionic liquids to generate and control the porous structure, reaching a density reduction of about 4 times and pore sizes down to 240 nm. Because of the low dispersion ability of the nanocharges in the aramid matrix, we carried out a novel functionalization process in which nanocharges were chemically modified by anchoring a polyamide model to their surface. Then, we tested the different behavior of the aramid films reinforced with neat and functionalized nanocharges, observing that functionalization led to better nanocharges dispersion, reduction of pore size from the micrometer to the nanometer range and the improvement of the mechanical behavior, resulting in higher relative Young's moduli values (around 60% higher in porous aramids reinforced with functionalized nanocharges)., FEDER (Fondo Europeo de Desarrollo Regional) and both the Spanish Agencia Estatal de Investigación (MAT2017–84501-R) and the Consejería de Educación-Junta de Castilla y León (BU306P18)

We have prepared solid sensory materials for the visual detection of cyanide in 100% water solutions and gas phases. The materials are hybrid polymers that were prepared from a palladium-containing acrylic monomer for use as sensory films and smart textiles.

We prepared microporous aramid films through a simple, inexpensive and green way, using ionic liquids (IL) as porosity promoters. Commercial poly(m-phenylene isophthalamide) (MPIA) films with different IL proportions were prepared, and then microporous films were obtained by removing the IL in distilled water. Microporous films presented density values between 0.34 and 0.71 g⋅cm (around five times lower to commercial MPIA), with a homogeneous and controlled cellular morphology dependent on the proportion of the IL, showing cell sizes in the microcellular range (radii between 1 and 8 µm). Thermal, mechanical and electrical properties (specifically ionic conductivity) of the aramid films were analyzed to evaluate the influence of the IL proportion. Finally, it was observed that the MPIA/IL system presented a reversible thermally induced phase-separation process around 60 °C, which was characterized through AFM-Raman images and spectra, together with the variation of the ionic conductivity., The financial support provided by FEDER (Fondo Europeo de Desarrollo Regional) and both the Spanish Agencia Estatal de Investigación (MAT2017-84501-R) and the Consejería de Educación- Junta de Castilla y León (BU306P18) is gratefully acknowledged.

We have prepared high-performance functional aromatic polyamides with sensory pendant groups toward amines. These polymers are colourless. The pendant groups have bromonaphthalimide motifs that react with amines rendering coloured arylamines by nucleophilic aromatic substitution of the halide. Thus, these materials are colorimetric sensors toward amines. In the interest of saving costs, while having a sensory material with a high specific surface, cotton fabrics were coated, in order to render coated fibres as smart colorimetric labels toward amines. Moreover, as fish spoilage by microorganism increases the biogenic amines in food, we have applied the smart labels to visually follow the food spoilage. Also, a picture taken to the films allowed to obtain, in seconds, the digital colour definition parameters (RGB) that were correlated with the results of expensive and time-consuming conventional techniques used to obtain relevant food quality data, such as total amine concentration (treatment of the sample and HPLC), colony-forming unit (microbiological assays), total volatile basic nitrogen (TVB-N), and organoleptic test (sensory test). The smart labels are inexpensive, granting in seconds the visual qualitative evaluation of the food quality, or even quantitative, and they comply with the European food contact materials regulation., FEDER (Fondo Europeo de Desarrollo Regional), and both the Spanish Ministerio de Economía, Industsria y Competitividad (MAT2017-84501-R) and the Consejería de Educación—Junta de Castilla y León (BU061U16)

This work describes the preparation of intrinsically blue-colored, high-performance aromatic polyamides (aramids). The color was achieved by preparing a diamine monomer containing a chromogenic azadipyrromethene (ADPM) core, which after polymerizing it with commercially available m -phenyleneisophtahlamide and isophthaloyl chloride gave the blue-colored polyisophthalamide copolymers. These materials were structurally compared to commercialized and high-value-added meta -aramid fibers [poly( m -phenyleneisophthalamide), MPIA , brand names: NOMEX ® and Teijinconex ® ]. Blue is the highest demanded color in the market of protective aramid fibers. The coloration efficiency of this special monomer is very high. Furthermore, the aramids showed even better thermal properties than commercial MPIA .

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., FEDER and both the Spanish Ministerio de Economía, Industria y Competitividad (MAT2014-54137-R) and the Consejería de Educación—Junta de Castilla y León (BU061U16)

We have prepared a solid sensory polymer kit to detect and quantify the water in organic solvents, as well as the ambient humidity; these determinations are cheap, easy and rapid with our new material. The limit of detection of water is 7 × 10−4% in acetone, 4 × 10−3% in THF, and 3 × 10−4% in toluene. Additionally, the relative humidity in air can be measured between 20% and 100%.

The use of supercritical CO2 (ScCO2) has been established as a standard technique to produce micro- and nanocellular polymers with controlled morphologies and cell sizes between 500 nm and several microns. However, overcoming the gap between micro and nanocellular polymers implies the use of long saturation times (up to several days) and low temperatures (below 0 °C) combined with high saturation pressures (above 30 MPa). This work presents a different approach to obtain microporous poly (methyl methacrylate) (PMMA) structures with controlled morphologies using a physical procedure employing ionic liquids that are mixed in solution with PMMA. The ionic liquid can produce interesting fine microporous materials simply by being removed with distilled water. The work compares the two fabrication methods previously mentioned to critically analyze the benefits and drawbacks of each preparation route. The method in this paper opens the possibility to obtain microporous polymers by employing ionic liquids, thus reducing the time of processing, avoiding specific foaming equipment and broadening the applicability of crosslinked and semi crystalline polymers. Low velocity tensile test results are also presented to point out the improvement in the mechanical parameters of microporous films obtained from ionic liquids compared to those of films foamed using ScCO2.

This work describes the design of efficient, inexpensive and easily prepared selective sensory polymers with chemically anchored amine groups as 2,4,6-trinitrotoluene (TNT)-sensing motifs as materials for the selective visual detection of TNT in aqueous media and as vapours. The materials are prepared as handleable sensory films or dense membranes from which sensory discs are cut, as well as smart fibres by coating conventional and commercial cotton fabrics. Both types of material exhibited a highly visible colour development from colourless to red upon contact with TNT both in the gas phase and in solution, and the colour change was used to build titration curves using the colour definition parameters of a digital image acquired with a smartphone, i.e., the RGB system. The materials were selective, remaining silent with other nitroaromatic compounds, such as 4-nitrotoluene and 2,4-dinitrotoluene, and the detection limit in solution was close to the micromolar range.

Aromatic polyamides are high performance materials with superior thermal and mechanical properties which make them extremely useful for advanced technologies. These polymers can be transformed into high-tensile strength synthetic fibers and into flame and cut-resistant materials that have technological applications in the field of coatings and fillers in the aerospace and armaments industry, in asbestos substitutes, electrical insulation, bullet-proof body armor, industrial filters, and sports fabrics, among others. This article sets out to review the existing literature and recent patent claims that describe the design, the preparation and the applications of wholly aromatic polyamides, semiaromatic polyamides and poly(amide imide)s.

Colorimetric cation responsive water soluble polymers and manageable films or membranes have beendesigned. The sensory materials respond with a colour change to the presence in water of Fe(III), Co(II),Cu(II), and Sn(II). The colour change is specific of each metal cation, and enables its identification (purplefor iron, orange for cobalt, green for copper, and yellow for tin). The design of the materials relies onan addition monomer having a terpyridine moiety, which behaves as a dye in presence of transitionmetal cations due to its proven chelating capability towards these species and the colour developmentthat always accompany the metallic complex formation. Water solutions of the sensory linear polymersallow for the UV/vis titration of Fe(III), Co(II), Cu(II), and Sn(II) with a limit of detection of 1.3 × 10−7,6.4 × 10−8, 1.3 × 10−5and 1.4 × 10−5M, respectively. On the other hand, sensory kits, cut from sensorymembranes, permitted the visual quantification of the cations in a dynamic range of five decades (1 × 10−7to 5 × 10−3M) for Fe(III) and Co(II) and of two decades (9 × 10−5to 9 × 10−3M) for Cu(II) and Sn(II).Titration curves can also be drawn from a picture taken to the sensory kits with a smartphone, by usingthe digital colour definition of the materials as analytical signal. Also, after entering into contact withhands, shapes of metallic objects (iron and cobalt containing tools) can be colour revealed by pressingthe hands on paper or cotton fabrics wetted with water solutions of the linear sensory polymer., Spanish Ministerio deEconomía y Competitividad-Feder (MAT2014-54137-R)

El trabajo que conforma Tesis Doctoral titulada Polímeros funcionales. Aplicaciones como sensores y materiales de altas prestaciones se encuadra en el ámbito científico y tecnológico de los materiales avanzados para aplicaciones específicas. En este marco se han diseñado materiales funcionales con aplicaciones en protección y seguridad civil, industria y medio ambiente. Concretamente se han elaborado sensores químicos poliméricos cromogénicos y fluorogénicos de explosivos (TNT), cationes metálicos, alta acidez y agua. Los receptores orgánicos utilizados son insolubles en agua, pero su incorporación a polímeros con el grado de hidrofilia adecuada ha permitido la obtención de polímeros solubles en este medio, así como geles capaces de detectar a las moléculas de interés en entornos acuosos. Además, se han preparado materiales de altas prestaciones, concretamente poliamidas aromáticas, con grupos funcionales que aportan características de interés como color, potencial funcionalización adicional, o mejores propiedades mecánicas y térmicas., The work constituting this Thesis lies within the scientific and technological field of advanced materials for specific applications. In this framework, functional materials with applications in civil protection and security, industry and environment have been designed. Specifically, fluorogenic and chromogenic polymeric chemosensors towards explosives (TNT), metal cations, high acidity and water were developed. The organic receptors used were insoluble in water, but their incorporation into polymers with the appropriate degree of hydrophilicity allowed for the preparation of water soluble polymers, as well as gels capable of detecting target molecules in aqueous environments. In addition, high performance materials were prepared, particularly aromatic polyamides containing functional groups that provide interesting features, such as color, additional functionalization potential, or better mechanical and thermal properties.

We synthesized a solid sensory material for the extraction, detection and quantification of iron(III) in aqueous media. The material is a film-shaped colorless polymer membrane that exhibits gel behavior. The Fe(III) extraction and sensing characteristics are imparted by a new monomer derived from a natural product (i.e., Kojic acid), which exhibits chelating properties toward Fe(III). The sorption of Fe(III) on the membrane in water has been thoroughly characterized, including the sorption kinetics, sorption isotherms and profiles as a function of the pH. Fe(III) sorption followed pseudo first-order kinetics and required approximately 30 min to reach equilibrium. The maximum sorption capacity was approximately 0.04 mmol/g, and the sorption isotherms are well modeled by the Langmuir equation. The complexes that were found in the solid phase are in good agreement with those previously identified in the aqueous phase. Moreover, the sorption is highly specific (i.e., a recognition process) and results from the formation of a colored complex (iron(III)-Kojic acid derivative moieties). Therefore, the colorless sensory membrane turns red upon immersion in aqueous solutions containing Fe(III). The color output allows for both the qualitative visual determination of the Fe(III) concentration as well as also titration of Fe(III) using a) a UV/vis technique (limit of detection of 3.6 × 10−5 M; dynamic range of five decades, lower concentration = 1.65 × 10−6 M) and b) a computer vision-based analytical chemistry approach via color definition of the sensory membrane (RGB parameters) obtained from an image recorded with a handy device (e.g., a smartphone) (limit of detection of 2.0 × 10−5 M)., Spanish Ministerio de Economía y Competitividad-Feder (MAT2011-22544 and MAT2014-54137-R) and by the Consejería de Educación – Junta de Castilla y León (BU232U13)

This study developed sensory polymeric materials for the colorimetric sensing of TNT in aqueous media. Solid films and coated fabrics permitted the detection of TNT, through colour change, and its quantification, by taking a picture of the materials and processing their RGB parameters to define the evolved colour.