Recent developments in sensing devices based on polymeric systems

This review is focused on the analysis of recent developments in the application of polymers in the detection and quantification of target species. The work begins with a description of the polymers that are employed as sensory materials, covering molecularly imprinted polymers or MIPs, hybrid polymers, acrylic polymers, conductive polymers, polymers with chiral motifs and also the use of polymeric arrays. After the description of the sensory polymers, the different target species which can be detected using sensory polymeric devices, including metallic cations and anionic species, gases, explosives, radionuclides and bacteria or the recent biomedical and biological applications is described. Finally, the sensory devices fabricated using smart polymers, including, for example, sensory devices based on Quartz Crystal Microbalances or the use of micro and nanoporous materials as substrates for sensory polymeric coatings is listed and reviewed. The work also details the different detection mechanisms based on the type of response of the sensory polymers, such as electrical, piezoelectric or fluorescence. In brief, the review details a review of the research work published in the last 10 years in this quickly evolving field, with special emphasis in the biomedical and biological applications, which have emerged recently raising great attention. To conclude, some perspectives and future challenges that must be overcome by this research field in the next years is exposed.FEDER (Fondo Europeo de Desarrollo Regional) and the Spanish Agencia Estatal de Investigación (AEI) (MAT2017-84501-R

Structural, thermal, and mechanical properties of gelatin-based films integrated with tara gum

Films with different morphology can be obtained by mixing fish gelatin, Tara gum and glycerol in different ratio and by subjecting the Tara gum to a ball milling treatment before its use. The amount of the plasticizer glycerol, as well as the type of Tara gum employed (as received or milled) resulted, from SEM and AFM analyses, to strong influencing the morphology of the films and their density. Also, the morphological differences determine different thermal and mechanical behaviours. In particular, the employment of milled Tara gum allows to improve the thermal stability, as well as the mechanical properties of the polymers. A similar outcome can be obtained by increasing the glycerol content, which can be used up to 20 wt%. Glycerol amounts exceeding that percentage, are detrimental for the quality of the films and reduce their thermal and mechanical performances.FEDER (Fondo Europeo de Desarrollo Regional) and both the Spanish Agencia Estatal de Investigacióon (MAT2017–84501-R; MAT2017-88923-P) and the Consejería de Educación, Junta de Castilla y León (BU306P18

Smart polymers in micro and nano sensory devices

The present review presents the most recent developments concerning the application of sensory polymers in the detection and quantification of different target species. We will firstly describe the main polymers that are being employed as sensory polymers, including, for example, conducting or acrylate-based polymers. In the second part of the review, we will briefly describe the different mechanisms of detection and the target species, such as metal cations and anions, explosives, and biological and biomedical substances. To conclude, we will describe the advancements in recent years concerning the fabrication of micro and nano sensory devices based on smart polymers, with a bibliographic revision of the research work published between 2005 and today, with special emphasis on research work presented since 2010. A final section exposing the perspectives and challenges of this interesting research line will end the present review article.FEDER (Fondo Europeo de DEsarrollo Regional), and both the Spanish Ministerio de Economía, Industria y Competitividad (MAT2014-54137-R, MAT2017-84501-R) and the Consejería de Educación–Junta de Castilla y León (BU061U16

Photopolymerization of ionic liquids in flexible microporous aramids for ion conductive solid polyelectrolytes

This work presents the preparation of novel solid polymer electrolytes based on flexible microporous aramids filled with photopolymerized ionic liquids and lithium salt. The materials combined a high ionic conductivity with the mechanical and thermal characteristics of the aramids, including also good flexibility and handleability. First, a simple casting process was followed to obtain microporous aramids with an interconnected channel morphology. In a second step, this channel structure was filled with a solution of non-commercial photopolymerizable ionic liquid, commercial ionic liquids and the lithium salt, followed by UV irradiation to obtain the conducting aramids. Ionic conductivity of the materials was studied at 25 °C, and also in the temperature range between −50 to 90 °C, together with SEM analyses of the filled porous structure and thermal properties, to fully characterize the photopolymerization process of the ionic liquids inside the porous structure. The materials showed high ionic conductivity values together with excellent thermal and mechanical properties, indicating their viability as flexible and thermally stable solid electrolytes.FEDER (Fondo Europeo de Desarrollo Regional) and both the Spanish Ministerio de Economía, Industria y Competitividad (MAT2017-84501-R and MAT2017-88923-P), the Consejería de Educacion-Junta ´ de Castilla y Leon ´ (BU306P18) and the Spanish Ministerio de Ciencia e Innovacion ´ (PID2019-108583RJ-I00/AEI/10.13039/501100011033)

Polymer-based chemical sensors

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Microcellular polymeric foams based on 1‐vinyl‐2‐pyrrolidone and butyl‐acrylate with tuned thermal conductivity

Microcellular polymers have been produced by ScCO2 foaming, based on 1-vinyl-2-pyrrolidone (VP) and butyl-acrylate (BA). Three different copolymers were prepared, varying the compositions of VP and BA, following a simple radical polymerization process using an UV initiator. The samples a good foaming behavior and also excellent flexibility and handle ability, with expansion ratios between 1.53 and 1.72, and cell sizes in the microcellular range (below 5 mm). However, it was observed that the gas distribution and, consequently, the cellular structure inside the polymer foams was highly dependent on the VP and BA proportions, leading to very different thermal conductivity values, even for similar volume gas fraction values. These results were related to the copolymer nanostructuration, which seems to have an influence in the final pore structure, thus opening the possibility of designing microcellular foams with similar macroscopic characteristics but different thermal conductivity valuesFEDER and both the Spanish Ministerio de Economıa y Competitividad (MAT2014–54137-R) and the Consejerıa de Educacion-Junta de Castilla y Leon (BU061U16

Microcellular polymer films based on cross-linked 1-vinyl-2-pyrrolidone and methyl methacrylate

A series of cross-linked copolymer films based on 1-vinyl-2-pyrrolidone and methyl methacrylate were produced using different poly(ethylene glycol) dimethacrylates as cross-linking agents. The average molecular mass of the cross-linking agent was varied, then allowing the foaming process using supercritical CO2 (ScCO2), obtaining microcellular films with different cellular structures as a function of the molecular mass of the cross-linking agent. The chemical structure, swelling behavior, CO2 uptake and cellular morphology of the materials were studied. Finally, the influence of the different cross-linking agents in the mechanical properties was also evaluated by measuring the tensile properties of the microcellular films.Fondo Europeo de Desarrollo Regional (FEDER) and the Spanish Agencia Estatal de Investigación (AEI) (MAT2017-84501-R

Easy and inexpensive method for the visual and electronic detection of oxidants in air by using vinylic films with embedded aniline

Conventional nonconductive vinylic films with dispersed aniline change their color and become conductive in the presence of specific oxidant gases, namely, chlorine and hydrogen peroxide. The color change arises from the polymerization of the aniline to yield the conjugated polymer polyaniline, which at the same time renders the flexible vinylic films conductive. We present a simple and straightforward method using both colorimetric and electrical responses to detect and quantify the presence of oxidants (Cl2 and H2O2) in the air. Using RGB analysis (red, green and blue parameters defining the colors in digital pictures on a computer display) based on different pictures taken with a smartphone of discs extracted from the films and by measuring the UV–vis spectral variation in the presence of different concentrations of Cl2 and H2O2, we obtained limits of detection and quantification between 15 and 200 ppbv for H2O2 and between 37 and 583 ppbv for Cl2. Additionally, the electrical response was measured using a fabricated device to visually detect the electrical conductivity activation of the sensor in the presence of oxidant atmospheres, detecting a rapid decrease in resistivity (three orders of magnitude) when the polymerization of aniline began, changing the film from non-conductive to conductive.FEDER (Fondo Europeo de Desarrollo Regional) and the Spanish Agencia Estatal de Investigación (AEI) (MAT2017-84501-R

Sensory polymeric foams as a tool for improving sensing performance of sensory polymers

Microcellular sensory polymers prepared from solid sensory polymeric films were tested in an aqueous Hg(II) detection process to analyze their sensory behavior. First, solid acrylic-based polymeric films of 100 µm thickness were obtained via radical copolymerization process. Secondly, dithizone sensoring motifs were anchored in a simple five-step route, obtaining handleable colorimetric sensory films. To create the microporous structure, films were foamed in a ScCO2 batch process, carried out at 350 bar and 60 °C, resulting in homogeneous morphologies with cell sizes around 5 µm. The comparative behavior of the solid and foamed sensory films was tested in the detection of mercury in pure water media at 2.2 pH, resulting in a reduction of the response time (RT) around 25% and limits of detection and quantification (LOD and LOQ) four times lower when using foamed films, due to the increase of the specific surface associated to the microcellular structure.Fondo Europeo de Desarrollo Regional) and both the Spanish Agencia Estatal de Investigación (MAT2017-84501-R) and the Consejeria de Educación-Junta de Castilla y León (BU306P18

Segmented-block poly(ether amide)s containing flexible polydisperse polyethyleneoxide sequences and rigid aromatic amide moieties

We describe the synthesis and characterization of three novel aromatic diamines containing oxyethylene sequences of different lengths. These diamines were polymerized using the low-temperature solution polycondensation method with isophthaloyl chloride (IPC), terepthaloyl chloride (TPC), [1,1’-biphenyl]-4,4’-dicarbonyl dichloride (BDC), and 4,4′-oxybis(benzoyl chloride) (OBE), obtaining twelve poly(ether amide)s with short segments of polydisperse polyethyleneoxide (PEO) sequences in the polymer backbone. These polymers show reasonably high molecular mass materials (Mw > 12,000), and the relationship between their structure and properties has been carefully studied. Compared with conventional polyamides containing monodisperse PEO sequences, the polydispersity of the PEO segments within the structural units exerts a significant influence on the crystallinity, flexibility, solubility, and the thermal properties of the polymers. For instance, the all-para oriented polyamides (TPCP-A), with an average number of 8.2 ethylenoxide units per structural unit can be transformed conventionally (Tm = 259 °C) in comparison with thermally untransformable polymer with 2 ethylenoxide units (Tm = 425 °C)FEDER (Fondo Europeo de Desarrollo Regional), the Spanish Agencia Estatal de Investigación (PID2020-113264RB-I00/AEI/10.13039/501100011033) and (PID2019-108583RJ-I00/AEI/ 10.13039/501100011033), and the Consejería de Educación—Junta de Castilla y León (BU306P1