Technological progress strongly relies on the development of high-performance materials. However, numerous environmental problems associated with the over-exploitation of fossil resources made the process of material design much more demanding and, in particular, sustainable. In this context, the idea behind the present dissertation is to create a biobased conductive nanocomposite material for potential applications in various advanced areas. Specifically, the nanocomposite consists of a poly(ε-caprolactone) (PCL) matrix functionalized with silver nanowires (AgNWs). The main asset of this material is its biobased nature, as well as its improved mechanical and electroconductive performance. Firstly, silver nanowires were synthesized via the polyol method, and characterized by ultraviolet-visible (UV-vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Secondly, the PCL-based nanocomposite films with different percentages of AgNWs, namely 1, 2, 3 and 7.5% (w/w), were fabricated via the simple and fast solvent casting film-processing methodology. The ensuing nanocomposite films were characterized by Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, XRD, SEM, SEM/EDS mapping, thermogravimetric analysis (TGA), tensile tests, dynamic mechanical analysis (DMA), and dielectric measurements. Overall, the synthetized AgNWs were highly crystalline and presented a needle-like morphology. The incorporation of these nanowires into the PCL matrix generated nanocomposite films with thermal stability up to almost 325°C and good mechanical performance with Young’s modulus values higher than 350 MPa. Moreover, the electrical conductivity (σAC) of the PCL-based films was evaluated by impedance spectroscopy and reached a maximum value of 5.7×10-6 S m–1 (at 235 K and 1.0×106 Hz) for the nanocomposite with the highest content of AgNWs (7.5%, PCL/AgNWs_7.5). All the obtained results revealed the potentiality of these thermoplastic nanocomposite films as biobased electroconductive materials for advanced applications.

Materials with the capacity to transform mechanical stresses into electrical energy and vice versa include piezoelectric polymers and polymer composites. The chapter introduces the piezoelectric effect and discusses polymer composites, emphasizing the polymer matrix and fillers to enhance performance and tune specific materials characteristics. We illustrate the versatility of these materials by analyzing the impact of filler type, size, and distribution on the composite’s piezoelectric response and its potential applications in biomedical devices, sensors, actuators, and energy harvesting. Lastly, we discuss present issues and needed advancements, such as the development of eco-friendly piezoelectric polymers and composites, which will further promote technological development and implementation.

Rapid technological developments in biomedicine, sensors, actuators and energy areas are taken place in the context of the global digital transformation, supported by the “Industry 4.0″ and “Internet of Things” (IoT) concepts. Those developments must include circular economy considerations in the scope of the 2030 sustainable developments goals to ensure easy access to affordable, sustainable, reliable, and modern services for all. To fulfil these advances, materials with high-performance based on biopolymers with tailored dielectric, magnetic and conducting properties are needed for improving devices performance while reducing environmental impact. Within this scope, bio-based resources are considered as next-generation materials for a broader range of applications. In this context, we present on the molecular structure, organization, main physical-chemical and functional properties of the most promising biopolymers. Further, the various possible modifications and processing methods are discussed to reach specific morphological, structural and/or functional characteristics. Finally, bio polymers-based blends and composites are discussed, alongside with their main application areas, opportunities, and challenges.

Fibrous materials are finding widespread applications in diversified areas, starting from clothing sector to medical fields, various structural and infrastructural applications of civil engineering, aerospace industries and even for energy harvesting and storage applications. In this paper, the results of various research activities conducted by the Fibrous Materials Research Group (FMRG), University of Minho to explore fibrous materials in several advanced and emerging applications have been presented and discussed.

Fibrous materials are finding widespread applications in diversified areas, starting from clothing sector to medical fields, various structural and infrastructural applications of civil engineering, aerospace industries and even for energy generation and storage applications. In this paper, some of the most recent research studies on the application of fibrous materials in various advanced sectors have been reviewed and presented.