Itxaso Azcune

Facile and Scalable Synthesis of Nanoporous Materials Based on Poly(ionic liquid)s

A simple, fast, sustainable, and scalable strategy to prepare nanoporous materials based on poly(ionic liquid)s (PILs) is presented. The synthetic strategy relies on the radical polymerization of crosslinker-type ionic liquid (IL) monomers in the presence of an analogous IL, which acts as a porogenic solvent. This IL can be extracted easily after polymerization and recycled for further use. The great advantages of this synthetic approach are the atom-efficiency and lack of waste. The effects of different monomer/porogen ratios on the specific surface area, porosity, and pore size have been investigated. Finally, the potential of the materials as CO2 sorbents has been evaluated.

Poly(vinylbenzyl chloride)-based poly(ionic liquids) as membranes for CO2 capture from flue gas

Over the last decade, membrane-based CO2 capture using ionic liquids (ILs) has been demonstrated as a promising technology. However, elaborative synthesis of monomers and long-term instability of IL-based composite membranes have so far limited their industrial relevance. In this paper, novel membranes are introduced for CO2 separation using poly(ionic liquids) (PILs) based on polyvinylbenzyl chloride (PVBC). Three PIL-based membranes were prepared as thin-film composites (TFC) by solvent casting with subsequent sealing. They were tested for the CO2 removal from synthetic flue gas. An ammonium-derivatised PVBC-analogue was prepared as a first PIL-type by polymerisation of an IL monomer, whereas two other PILs, respectively with hydroxyethyl ammonium and pyrrolidinium cations, were obtained using a modification of commercial PVBC. Introduction of bis(trifluoromethylsulfonyl)imide (Tf2N) anions was accomplished by metathesis. A thorough characterisation of the material structure, composition, membrane morphology and gas separation properties demonstrates that the presence of hydroxyl groups in the polycation enhanced the interaction with CO2 molecules. The mixed-gas selectivity increases with the higher positive charge on the cation species (hydroxyethyl-dimethylammonium > trimethylammonium > pyrrolidinium). More importantly, experiments performed in humidified conditions particularly revealed a doubled CO2 permeance and a 20–30% increased selectivity in comparison to dry conditions. These developments are spurring the application of PIL-based TFC membranes for CO2 capture from flue gas streams.

Functionalization of Cellulose Nanocrystals in Choline Lactate Ionic Liquid

Cellulose nanocrystals (CNCs) are valuable nanomaterials obtained from renewable resources. Their properties make them suitable for a wide range of applications, including polymer reinforcement. However, due to their highly hydrophilic character, it is necessary to modify their surface with non-polar functional groups before their incorporation into a hydrophobic polymer matrix. In this work, cellulose nanocrystals were modified using a silane coupling agent and choline lactate, an ionic liquid derived from renewable resources, as a reaction medium. Modified cellulose nanocrystals were characterized by infrared spectroscopy, showing new peaks associated to the modification performed. X-ray diffraction was used to analyze the crystalline structure of functionalized cellulose nanocrystals and to optimize the amount of silane for functionalization. Poly(lactic acid) (PLA) nanocomposites containing 1 wt % of functionalized cellulose nanocrystals were prepared. They were characterized by field-emission scanning electron microscopy (FE-SEM) and mechanical tests. The use of choline lactate as reaction media has been shown to be an alternative method for the dispersion and silanization of the cellulose nanocrystals without the addition of an external catalyst.

Fully Biodegradable Biocomposites with High Chicken Feather Content

The aim of this work was to develop new biodegradable polymeric materials with high loadings of chicken feather (CF). In this study, the effect of CF concentration and the type of biodegradable matrix on the physical, mechanical and thermal properties of the biocomposites was investigated. The selected biopolymers were polylactic acid (PLA), polybutyrate adipate terephthalate (PBAT) and a PLA/thermoplastic copolyester blend. The studied biocomposites were manufactured with a torque rheometer having a CF content of 50 and 60 wt %. Due to the low tensile strength of CFs, the resulting materials were penalized in terms of mechanical properties. However, high-loading CF biocomposites resulted in lightweight and thermal-insulating materials when compared with neat bioplastics. Additionally, the adhesion between CFs and the PLA matrix was also investigated and a significant improvement of the wettability of the feathers was obtained with the alkali treatment of the CFs and the addition of a plasticizer like polyethylene glycol (PEG). Considering all the properties, these 100% fully biodegradable biocomposites could be adequate for panel components, flooring or building materials as an alternative to wood–plastic composites, contributing to the valorisation of chicken feather waste as a renewable material.

Chapter Poly(Ionic Liquid)s and Nanoobjects

This chapter describes the different applications of Poly(ionic liquid)s in nanotechnology, including nanocomposites and nanodevices.

Flexible Biocomposites with Enhanced Interfacial Compatibility Based on Keratin Fibers and Sulfur-Containing Poly(urea-urethane)s

Feathers are made of keratin, a fibrous protein with high content of disulfide-crosslinks and hydrogen-bonds. Feathers have been mainly used as reinforcing fiber in the preparation of biocomposites with a wide variety of polymers, also poly(urea-urethane)s. Surface compatibility between the keratin fiber and the matrix is crucial for having homogenous, high quality composites with superior mechanical properties. Poly(urea-urethane) type polymers are convenient for this purpose due to the presence of polar functionalities capable of forming hydrogen-bonds with keratin. Here, we demonstrate that the interfacial compatibility can be further enhanced by incorporating sulfur moieties in the polymer backbone that lead to new fiber-matrix interactions. We comparatively studied two analogous thermoplastic poly(urea-urethane) elastomers prepared starting from the same isocyanate-functionalized polyurethane prepolymer and two aromatic diamine chain extenders, bis(4-aminophenyl) disulfide (TPUU-SS) and the sulfur-free counterpart bis(4-aminophenyl) methane (TPUU). Then, biocomposites with high feather loadings (40, 50, 60 and 75 wt %) were prepared in a torque rheometer and hot-compressed into flexible sheets. Mechanical characterization showed that TPUU-SS based materials underwent higher improvement in mechanical properties than biocomposites made of the reference TPUU (up to 7.5-fold higher tensile strength compared to neat polymer versus 2.3-fold). Field Emission Scanning Electron Microscope (FESEM) images also provided evidence that fibers were completely embedded in the TPUU-SS matrix. Additionally, density, thermal stability, and water absorption of the biocomposites were thoroughly characterized.