Polyurethane–poly(vinylidene fluoride) (PU–PVDF) thin film composite membranes for gas separation

Engineering Dental Tissues Using Biomaterials with Piezoelectric Effect: Current Progress and Future Perspectives

Dental caries and traumatic injuries to teeth may cause irreversible inflammation and eventual death of the dental pulp. Nevertheless, predictably, repair and regeneration of the dentin-pulp complex remain a formidable challenge. In recent years, smart multifunctional materials with antimicrobial, anti-inflammatory, and pro-regenerative properties have emerged as promising approaches to meet this critical clinical need. As a unique class of smart materials, piezoelectric materials have an unprecedented advantage over other stimuli-responsive materials due to their inherent capability to generate electric charges, which have been shown to facilitate both antimicrobial action and tissue regeneration. Nonetheless, studies on piezoelectric biomaterials in the repair and regeneration of the dentin-pulp complex remain limited. In this review, we summarize the biomedical applications of piezoelectric biomaterials in dental applications and elucidate the underlying molecular mechanisms contributing to the biological effect of piezoelectricity. Moreover, we highlight how this state-of-the-art can be further exploited in the future for dental tissue engineering.

Oxygen-Sensitive Photo- and Radioluminescent Polyurethane Nanoparticles Modified with Octahedral Iodide Tungsten Clusters

The development of cancer treatment techniques able to cure tumors located deep in the body is an urgent task for scientists and physicians. One of the most promising methods is X-ray-induced photodynamic therapy (X-PDT), since X-rays have unlimited penetration through tissues. In this work, octahedral iodide tungsten clusters, combining the properties of a scintillator and photosensitizer, are considered as a key component of nanosized polyurethane (pU) particles in the production of materials promising for X-PDT. Cluster-containing pU nanoparticles obtained here demonstrate bright photo- and X-ray-induced emission in both solid and water dispersion, great efficiency in the generation of singlet oxygen, and high sensitivity regarding photoluminescence intensity in relation to oxygen concentration. Additionally, incorporation of the cluster complex into the pU matrix greatly increases its stability against hydrolysis in water and under X-rays.

Understanding the langmuir and Langmuir-Schaefer film conformation of low-bandgap polymers and their bulk heterojunctions with PCBM

Low-bandgap polymers are widely used as p-type components in photoactive layers of organic solar cells, due to their ability to capture a large portion of the solar spectrum. The comprehension of their supramolecular assembly is crucial in achieving high-performance organic electronic devices. Here we synthezed two exemplar low-bandgap cyclopentadithiophene (CPDT):diketopyrrolopyrrole (DPP)-based polymers, with either a twelve carbon (C12) or a tri etyleneglycol (TEG) side chains on the DPP units (respectively denoted PCPDTDPP_C12 and PCPDTDPP_TEG). We deposited Langmuir-Schaefer films of these polymers blended with the widely used electron donor material [6,6]-phenyl-C61-butyric-acid methyl ester (PCBM). We then characterized the conformational, optical and morphological properties of these films. From the monolayers to the solid films, we observed distinct self-organization and surface properties for each polymer due to the distinct nature of their side chains. Emphasizing their attraction interactions with PCBM and the phase transitions according to the surface pressure. The elements amount on the surface, calculated through the XPS, gave us a good insight on the polymers' conformations. Through UV-visible absorption spectroscopy, the improvement in the PCPDTDPP film ordering upon PCBM addition is evident and we saw the contribution of the polymer units on the optical response. Chemical attributions of the polymers were assigned using FTIR Spectroscopy and Raman Scattering, revealing the physical interaction after mixing the materials. We showed that it is possible to build nanostructured PCPDTDPPs films with a high control of their molecular properties through an understanding of their self-assembly and interactions with an n-type material.

Solution Blow Spinning of Polyvinylidene Fluoride Based Fibers for Energy Harvesting Applications: A Review

Polyvinylidene fluoride (PVDF)-based piezoelectric materials (PEMs) have found extensive applications in energy harvesting which are being extended consistently to diverse fields requiring strenuous service conditions. Hence, there is a pressing need to mass produce PVDF-based PEMs with the highest possible energy harvesting ability under a given set of conditions. To achieve high yield and efficiency, solution blow spinning (SBS) technique is attracting a lot of interest due to its operational simplicity and high throughput. SBS is arguably still in its infancy when the objective is to mass produce high efficiency PVDF-based PEMs. Therefore, a deeper understanding of the critical parameters regarding design and processing of SBS is essential. The key objective of this review is to critically analyze the key aspects of SBS to produce high efficiency PVDF-based PEMs. As piezoelectric properties of neat PVDF are not intrinsically much significant, various additives are commonly incorporated to enhance its piezoelectricity. Therefore, PVDF-based copolymers and nanocomposites are also included in this review. We discuss both theoretical and experimental results regarding SBS process parameters such as solvents, dissolution methods, feed rate, viscosity, air pressure and velocity, and nozzle design. Morphological features and mechanical properties of PVDF-based nanofibers were also discussed and important applications have been presented. For completeness, key findings from electrospinning were also included. At the end, some insights are given to better direct the efforts in the field of PVDF-based PEMs using SBS technique.

Constructing anhydrous proton exchange membranes based on cadmium telluride nanocrystal-doped sulfonated poly(ether ether ketone)/polyurethane composites

Cadmium telluride (CdTe) nanocrystals with thiol stabilizers have been applied widely in the fields of energy storage and transformation. The aim of this work is to develop anhydrous proton exchange membranes (PEMs) by introducing CdTe nanocrystals bearing thioglycolic acid (tga) or mercaptopropionic acid (mpa) stabilizers into sulfonated poly(ether ether ketone) (SPEEK) and polyurethane (PU) systems. In the prepared SPEEK/PU/CdTe membranes, CdTe nanocrystals could provide desirable properties such as improving mechanical strength and enhancing proton conductivity by combining with phosphoric acid (PA) molecules. Successful preparation of SPEEK/PU/CdTe/PA membranes was demonstrated by the identification of high and stable proton conductivity and satisfactory thermal/chemical stability and mechanical properties. The fine appearance of membranes revealed uniform dispersion of components. Measurements of properties showed that the SPEEK(74%)/PU/CdTe-mpa(20/60/20)/100%PA membrane as a candidate anhydrous PEM is promising for use in high-temperature proton exchange membrane fuel cells. Specifically, the recommended membrane showed a proton conductivity of 1.18 × 10^-1 S cm^-1 at 160 °C and 3.96 × 10^-2 S cm^-1 at 100 °C, lasting for 600 h, and a tensile stress of 14.6 MPa at room temperature. Mixing inorganic CdTe nanocrystals with polymers to form inorganic/organic composite membranes is effective for producing anhydrous PEMs with cheaper polymers without functional groups to conduct protons.

Properties and Applications of the β Phase Poly(vinylidene fluoride)

Poly(vinylidene fluoride), PVDF, as one of important polymeric materials with extensively scientific interests and technological applications, shows five crystalline polymorphs with α, β, γ, δ and ε phases obtained by different processing methods. Among them, β phase PVDF presents outstanding electrical characteristics including piezo-, pyro-and ferroelectric properties. These electroactive properties are increasingly important in applications such as energy storage, spin valve devices, biomedicine, sensors and smart scaffolds. This article discusses the basic knowledge and character methods for PVDF fabrication and provides an overview of recent advances on the phase modification and recent applications of the β phase PVDF are reported. This study may provide an insight for the development and utilization for β phase PVDF nanofilms in future electronics.

Effects of ZnO Nanoparticle on the Gas Separation Performance of Polyurethane Mixed Matrix Membrane

Polyurethane (PU)-ZnO mixed matrix membranes (MMM) were fabricated and characterized for gas separation. A thermogravimetric analysis (TGA), a scanning electron microscope (SEM) test and an atomic-force microscopy (AFM) revealed that the physical properties and thermal stability of the membranes were improved through filler loading. Hydrogen Bonding Index, obtained from the Fourier transform infrared spectroscopy (FTIR), demonstrate that the degree of phase separation in PU-ZnO 0.5 wt % MMM was more than the neat PU, while in PU-ZnO 1.0 wt % MMM, the phase mixing had increased. Compared to the neat membrane, the CO₂ permeability of the MMMs increased by 31% for PU-ZnO 0.5 wt % MMM and decreased by 34% for 1.0 wt % ZnO MMM. The CO₂/CH₄ and CO₂/N₂ selectivities of PU-ZnO 0.5 wt % were 18.75 and 64.75, respectively.

Blend membranes based on polyurethane and polyethylene glycol: exploring the impact of molecular weight and concentration of the second phase on gas permeation enhancement

This work seeks to explore the permeability dependence of polyurethane (PU)/polyethylene glycol (PEG) blend membranes on the molecular weight and composition of PEG constituent polymer. In this regard, gases with different polar nature were mixed (CO2/N2, CO2/CH4, and O2/N2) and subjected to a series of PU/PEG blends prepared via solution casting method. With the alteration of the molecular weight (1000, 2000, and 6000 g/mol) and composition (0, 10, 15, and 20 wt.%) of PEG in the blend films, the potentials of membranes in controlling the permeation of gas molecules within the films were quantified, compared, and discussed. It is known that the introduction of PEG into PU-based membranes causes the films to become more flexible, which brings advantages from an application point of view. Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and scanning electron microscopy analyses were used to study the microstructural changes in the prepared PU/PEG blend membranes. The selectivity of the films was obviously displaced by the introduction of PEG, particularly when higher-molecular-weight PEGs were used and the resulting hybrid membranes were subjected to a mixture of CO2/CH4 or CO2/N2 gases.

Synthesis of an original fluorinated triethylene glycol methacrylate monomer and its radical copolymerisation with vinylidene fluoride. Its application as a gel polymer electrolyte for Li-ion batteries

The synthesis and characterisation of novel poly[VDF-g-oligo(EO)] graft copolymers are presented.

Synthesis and characterization of metal-containing poly(siloxane-urethane) crosslinked structures derived from siloxane diols and ferrocene diisocyanate

Ferrocene, siloxane and polyurethane moieties were combined for the first time in cross-linked materials with interesting electric and electro-chemical behavior.

Performance of an electrothermal swing adsorption system with postdesorption liquefaction for organic gas capture and recovery

The use of adsorption on activated carbon fiber cloth (ACFC) followed by electrothermal swing adsorption (ESA) and postdesorption pressure and temperature control allows organic gases with boiling points below 0 °C to be captured from air streams and recovered as liquids. This technology has the potential to be a more sustainable abatement technique when compared to thermal oxidation. In this paper, we determine the process performance and energy requirements of a gas recovery system (GRS) using ACFC-ESA for three adsorbates with relative pressures between 8.3 × 10(-5) and 3.4 × 10(-3) and boiling points as low as -26.3 °C. The GRS is able to capture > 99% of the organic gas from the feed air stream, which is comparable to destruction efficiencies for thermal oxidizers. The energy used per liquid mole recovered ranges from 920 to 52,000 kJ/mol and is a function of relative pressure of the adsorbate in the feed gas. Quantifying the performance of the bench-scale gas recovery system in terms of its ability to remove organic gases from the adsorption stream and the energy required to liquefy the recovered organic gases is a critical step in developing new technologies to allow manufacturing to occur in a more sustainable manner. To our knowledge, this is the first time an ACFC-ESA system has been used to capture, recover, and liquefy organic compounds with vapor pressures as low as 8.3 × 10(-5) and the first time such a system has been analyzed for process performance and energy consumption.

Capture and recovery of isobutane by electrothermal swing adsorption with post-desorption liquefaction

A bench-scale capture and recovery system to convert a low concentration organic gas to a liquid is described here. Adsorption of isobutane onto activated carbon fiber cloth (ACFC) followed by electrothermal desorption and subsequent liquefaction is demonstrated. Experimental conditions to condense desorbed isobutane were determined based on Dalton's law and Antoine's equation. Breakthrough curves for a gas stream containing 2000 ppm(v) isobutane in air adsorbing onto ACFC-15 demonstrate an adsorption capacity of 0.094 ± 0.017 g of isobutane/g of ACFC with >98% capture efficiency. The system described here utilizes two adsorbers, which operate cyclically to allow for continuous treatment of the isobutane. Adsorption followed by electrothermal desorption provided a concentration ratio of 240, which facilitates condensation of the isobutane after compression and cooling and is an order of magnitude greater than what has been previously demonstrated.