Diseño de polianilinas nanoestruturadas para aplicaciones termoeléctricas y sensores

Programa Oficial de Doutoramento en Física Aplicada. 5021V01[Resumen] Dentro del conjunto de los polímeros intrínsecamente conductores, la polianilina (PANI) presenta una gran versatilidad en cuanto a su síntesis y propiedades que la hacen adecuada para un amplio campo de aplicaciones. Dentro de este contexto, la presente tesis tiene como objetivo el diseño y caracterización de nuevas polianilinas que combinen buenas propiedades (eléctricas, termoeléctricas, estabilidad térmica o piezorresistivas) con un coste asequible y con menor impacto medioambiental. Para ello se estudió la influencia del HCl, DBSA (ácido dodecilbencensulfónico) y NaSIPA (sal de sodio del ácido 5-sulfoisoftálico) como dopantes y de distintas rutas de síntesis sencillas y respetuosas con el medio ambiente, para la obtención de las PANIs. Así mismo, con el fin de mejorar las propiedades mecánicas del polímero sintetizado y reducir costes, se elaboraron nuevos materiales compuestos utilizando acetato de polivinilo como matriz polimérica y polianilina como carga conductora. Tanto las polianilinas sintetizadas como sus compuestos se han caracterizado por TGA, FTIR, Análisis Elemental, XRD y TEM. Las propiedades eléctricas, termoeléctricas y piezorresistivas se han estudiado en función del tipo de dopante, tipo de síntesis y cantidad de polianilina (en el caso de los compuestos), analizando el potencial uso de estos materiales en sensores y generadores termoeléctricos. Entre los distintos polímeros estudiados: las PANIs dopadas con DBSA obtenidas tanto por ruta de síntesis directa como por la indirecta, muestran las mejores propiedades para su uso en sensores térmicos; sin embargo, la PANI-NaSIPA muestra la mejor eficiencia termoeléctrica; los materiales compuestos de látex con un 30% en masa de PANI-HCl presentaron la conductividad de la PANI original obteniendo un buen balance de propiedades piezorresistivas y coste económico.[Resumo] Dentro do conxunto dos polímeros intrinsecamente condutores, a polianilina (PANI) presenta unha grande versatilidade en canto a súa síntese e propiedades que a fan axeitada para un amplo campo de aplicacións. Neste contexto, a presente tese ten como obxecto o deseño e caracterización de novas polianilinas que combinen boas propiedades (eléctricas, termoeléctricas, estabilidade térmica ou piezorresistivas) cun custo asumíbel e con menor impacto medioambiental. Para iso, estudouse a influencia do HCl, DBSA (ácido dodecilbencensulfónico) e NaSIPA (sal de sodio do ácido 5-sulfoisoftálico) coma dopantes e distintas rutas de síntese, sinxelas e respectuosas co medio ambiente, na obtención das polianilinas. Ase mesmo, co fin de mellorar as propiedades mecánicas do polímero sintetizado e reducir custos, elaboráronse novos materiais compostos empregando acetato de polivinilo como matriz polimérica e a PANI como carga condutora. Tanto as polianilinas sintetizadas coma os seus compostos, caracterizáronse por TGA, FTIR, análise elemental, XRD e TEM. As propiedades eléctricas, termoeléctricas e piezorresistivas estudáronse en función do tipo de dopante, tipo de síntese e cantidade de polianilina (no caso dos compostos), para avaliar o potencial uso destes materiais en sensores e xeradores termoeléctricos. Entre os distintos polímeros estudados: as PANIs dopadas con DBSA, obtidas tanto por ruta de síntese directa como pola indirecta, amosaron as mellores propiedades para seu uso en sensores térmicos; con todo, a PANI-NaSIPA mostra a mellor eficiencia termoeléctrica; namentres que os materiais compostos de látex cun 30% en masa de PANI-HCl presentaron a condutividade da PANI orixinal, obtendo un bo balance entre as propiedades piezorresistivas e custo económico.[Abstract] Among the class of materials known as intrinsically conducting polymers, polyaniline (PANI) stands out due to the great versatility of synthetic methods and properties which greatly enlarge its fields of applications. Within this context, the scope of the present doctoral thesis is the design and characterization of novel polyanilines which combine suitable physical properties (electrical conductivity, thermoelectric performance, thermal stability or piezoresistivity) with affordability and less environmental impact. In order to fulfill this aim, the first part of this work studies the influence on PANI properties of HCl, dodecylbenzenesulfonic acid (DBSA) and 5- sulfoisophtalic acid sodium salt (NaSIPA) as dopants and several simple and ecofriendly synthetic routes. Furthermore, with the purpose of improving the mechanical properties of PANI together with cost reduction, new composite materials were designed using poly(vinyl acetate) (PVAc) as polymer matrix and PANI as conductive filler. Both doped PANIs and the PANI-PVAc composites had been analyzed by means TGA, FTIR, Elemental Analysis, XRD and TEM. The electrical, thermoelectric and piezoresistive properties had been studied as a function of the type of dopant, synthetic route and PANI content, in the case of the PANI-PVAc composites, so as to evaluate the potential application of these materials as sensors and thermoelectric generators. As a conclusion, PANI doped with DBSA and synthesized either by the so called “direct” or “indirect” routes, are the best candidates for thermal sensors; however, PANI-NaSIPA offers the highest thermoelectric efficiency, whereas polyaniline–poly(vinyl acetate) latex nanocomposites (PANI– PVAc) with 30% PANI-HCl (weight%), which preserve the conductivity values of pristine PANI, present a worthy compromise between piezoresistive properties and affordability

Thermoelectric properties and intrinsic conduction processes in DBSA and NaSIPA doped polyanilines

Seeking to gain fundamental understanding of the thermoelectric (TE) behavior of polyanilines (PANIs), structure- property relationships of PANI nanorods, doped with dodecylbenzenesulfonic acid (DBSA) and 5-sulfoisophtalic acid sodium salt (NaSIPA), and prepared by an indirect synthetic route, are discussed in terms of the contribution of the acid concentrations on the thermoelectric properties. The synergistic combination of high doping level and layer structure, accounts for the moderately high electrical conductivities (σ) and low constant Seebeck coefficients (α) of PANI-DBSA. Conversely, the poor doping ability of NaSIPA and low crystallinity degree explain the low electrical conductivities along with significant increases in Seebeck coefficient values. In relation to conduction mechanisms, PANI-DBSA shows a hopping behavior with a carrier concentration of c≈0.49 (hole type), while PANI-NaSIPA displays a diffusive regime, characteristic of degenerate metallic semiconductors, with an estimated charge carrier density of n≈3 × 1021 e/cm3

Piezoresistive polymer blends for electromechanical sensor applications

Doped polyaniline (PANI) exhibits excellent electrical properties that can be used in composite materials to replace metallic or carbonaceous nanofillers commonly used in composites for sensor applications. Polymer blends based on PANI and thermoplastic elastomer styrene-ethylene/butylene-styrene (SEBS) copolymer have been prepared by solvent casting showing large strain yield (>10% for 40 wt% PANI content), high electrical conductivity, 1 S/m, after the percolation threshold at ≈10 wt% PANI. Further, the composites show suitable piezoresistive response with gauge factor (GF) between GF ≈ 1.5 and 2.4 for deformations up to 10%. The overall properties of the solution casted PANI/SEBS blends indicate their suitability for advanced electromechanical sensors applications, with simple integration and processable by solution printing technologies.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. Financial support also provided by ERDF funds through the Portuguese Operational Programme for Competitiveness and Internationalization -COMPETE 2020, and national funds through FCT, under projects PTDC/EEI-SII/5582/2014 and PTDC/CTM-ENE/5387/2014. PC and JO thanks to FCT by financial support for the SFRH/BPD/110914/2015 and SFRH/BD/98219/2013 grants, respectively. Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support) and from the Basque Government Industry Department under the ELKARTEK and HAZITEK program are also acknowledged.info:eu-repo/semantics/publishedVersio

Piezoresistive response of extruded polyaniline/(styrene-butadiene-styrene) polymer blends for force and deformation sensors

Smart materials for sensor applications are increasingly being used in a wide variety of applications ranging from engineering to medical devices. This work reports on piezoresistive sensors based on conductive polyaniline and thermoplastic elastomer processed by conventional polymer extrusion. The material presents excellent processability and piezoresistive performance offering an alternative to traditional composites with conductive nanofillers for sensor applications. The polyaniline/ styrene-butadiene-styrene (PANI/SBS) conductive polymer blends present good mechanical properties, high electrical conductivity and piezoresistive response. The maximum strain reaches ≈60% for 30 weight percentage (wt%) PANI content and the electrical conductivity is σ ≈0.1 S/m for blends with 40 wt% PANI content. Further, the sample with 40 wt% PANI content shows a piezoresistive gauge factor GF ≈1 for deformation measurements between 0.1 to 3 mm in bending cycles.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. The authors thank the FCT for financial support under projects PTDC/EEI-SII/5582/2014 and PTDC/CTM-ENE/5387/2014. P. C. also thank the FCT for the SFRH/BPD/110914/2015 grant, as well POCH and European Union. Financial support from the Basque Government Industry Department under the ELKARTEK Program is also acknowledged as well as funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R and by Xunta de Galicia-FEDER though the Program of Consolidation and structuring competitive research units (GRC2014/036).info:eu-repo/semantics/publishedVersio

Multifunctional electromechanical and thermoelectric polyaniline-poly(vinyl acetate) latex composites for wearable devices

This paper reports on the piezoresistive, thermoresistive and thermoelectric behaviour of polymer-based nanocomposites, composed of polyaniline and poly(vinylacetate) latex (PANI/PVAc) matrix. The samples were prepared by simple, scalable, eco-friendly and low-cost latex technology with PANI concentrations spanning form 2.5 to loadings of 60 wt.%. The observed electrical and mechanical behaviour can be explained in the framework of the percolation theory. Specifically, stretchable PANI/PVAc films with PANI contents ranging from 10 to 30 wt.% are particularly useful for applications involving electrical conductivity with elastomeric performance. Due to the combination of the reinforcement effect of PANI and enhanced interfacial adhesion via H-bonding between PANI and the polymer matrix, they present higher Young´s modulus and tensile strength together with a slight decrease in ductility, compared to pure PVAc latex. PANI/PVAc ratio plays an important role in the electromechanical composites, both in the GF values and fatigue. Accordingly, the mechanical properties of PVAc latex, tailored with conductive PANI, can develop interesting electromechanical properties for sensors devices up to large deformations. This tunability together with the soft nature of composites paves the way for low-cost macroscale diverse and adaptable applications such as temperature sensing, mapping, and compensation in stretchable and wearable electronics.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, project PTDC/EEI-SII/5582/2014 and grant SFRH/BPD/110914/2015 (PC). The authors acknowledge funding by the Spanish ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry Department under the ELKARTEK and HAZITEK program. Bincheng Huang would like to thank the support from the China Scholarship Council.info:eu-repo/semantics/publishedVersio