Effect of blend composition on microstructure, morphology, and gas permeability in PU/PMMA blends

Poly Methacrylic Acid Sodium Salt (PMANa)/Polyurethane (PU) Latex-Polyelectrolyte Colloid Systems Enabling One-Pot Fabrication of Nonperiodic Structured Mechanoresponsive Smart Windows

Mechanoresponsive smart windows can modulate optical transparency by mechanical actuation, showing the advantages of low cost, energy efficiency, and chemical stability. To date, mechanoresponsive smart windows are mainly built on periodic nano- or microstructures such as arrays, wrinkles, 3D photonic crystals, and polymeric nanocomposites. However, the production of periodic structures requires multiple and complicated processes, which restricts large-scale manufacturing of mechanoresponsive smart windows for practical application. Here, we report one-pot fabrication of poly methacrylic acid sodium salt (PMANa)/polyurethane (PU) mechanoresponsive smart windows with a nonperiodic naturally occurring microsized structure. The obtained smart windows display a high contrast ratio and stable transparency switching behavior under 80% tensile strain over 1000 cycles and have a large breaking elongation of 820%. It offers a promising platform for designing and fabricating multifunctional optical devices including anticounterfeiting labels and dynamical light gratings.

Mechanically robust hydrophobic interpenetrating polymer network-based nanocomposite of hyperbranched polyurethane and polystyrene as an effective anticorrosive coating

Facile fabrication of Si/RGO reinforced interpenetrating polymer network-based nanocomposites with inherent surface hydrophobicity and anticorrosive attributes.

Development of Thermally Conductive Polyurethane Composite by Low Filler Loading of Spherical BN/PMMA Composite Powder

The issue of electronic heat dissipation has received much attention in recent times and has become one of the key factors in electronic components such as circuit boards. Therefore, designing of materials with good thermal conductivity is vital. In this work, a thermally conductive SBP/PU composite was prepared wherein the spherical h-BN@PMMA (SBP) composite powders were dispersed in the polyurethane (PU) matrix. The thermal conductivity of SBP was found to be significantly higher than that of the pure h-BN/PU composite at the same h-BN filler loading. The SBP/PU composite can reach a high thermal conductivity of 7.3 Wm^-1 K^-1 which is twice as high as that of pure h-BN/PU composite without surface treatment in the same condition. This enhancement in the property can be attributed to the uniform dispersion of SBP in the PU polymer matrix that leads to a three-dimensional continuous heat conduction thereby improving the heat diffusion of the entire composite. Hence, we provide a valuable method for preparing a 3-dimensional heat flow path in polyurethane composite, leading to a high thermal conductivity with a small amount of filler.

Influence of Blend Composition and Silica Nanoparticles on the Morphology and Gas Separation Performance of PU/PVA Blend Membranes

Polymer blending and mixed-matrix membranes are well-known modification techniques for tuning the gas separation properties of polymer membranes. Here, we studied the gas separation performance of mixed-matrix membranes (MMMs) based on the polyurethane/poly(vinyl alcohol) (PU/PVA) blend containing silica nanoparticles. Pure (CO₂, CH₄, N₂, O₂) and mixed-gas (CO₂/N₂ and CO₂/CH₄) permeability experiments were carried out at 10 bar and 35 °C. Poly(vinyl alcohol) (PVA) with a molecular weight of 200 kDa (PVA200) was blended with polyurethane (PU) to increase the CO₂ solubility, while the addition of silica particles to the PU/PVA blend membranes augmented the CO₂ separation performance. The SEM images of the membranes showed that the miscibility of the blend improved by increasing the PVA contents. The membrane containing 10 wt % of PVA200 (PU/PVA200–10) exhibited the highest CO₂/N₂~32.6 and CO₂/CH₄~9.5 selectivities among other blend compositions, which increased to 45.1 and 15.2 by incorporating 20 wt % nano-silica particles.

Response Characteristics of Hydrogen Sensors Based on PMMA-Membrane-Coated Palladium Nanoparticle Films

Coating a polymeric membrane for gas separation is a feasible approach to fabricate gas sensors with selectivity. In this study, poly(methyl methacrylate)-(PMMA-)membrane-coated palladium (Pd) nanoparticle (NP) films were fabricated for high-performance hydrogen (H₂) gas sensing by carrying out gas-phase cluster deposition and PMMA spin coating. No changes were induced by the PMMA spin coating in the electrical transport and H₂-sensing mechanisms of the Pd NP films. Measurements of H₂ sensing demonstrated that the devices were capable of detecting H₂ gas within the concentration range 0-10% at room temperature and showed high selectivity to H₂ due to the filtration effect of the PMMA membrane layer. Despite the presence of the PMMA matrix, the lower detection limit of the sensor is less than 50 ppm. A series of PMMA membrane layers with different thicknesses were spin coated onto the surface of Pd NP films for the selective filtration of H₂. It was found that the device sensing kinetics were strongly affected by the thickness of the PMMA layer, with the devices with thicker PMMA membrane layers showing a slower response to H₂ gas. Three mechanisms slowing down the sensing kinetics of the devices were demonstrated to be present: diffusion of H₂ gas in the PMMA matrix, nucleation and growth of the β phase in the α phase matrix of Pd hydride, and stress relaxation at the interface between Pd NPs and the PMMA matrix. The retardation effect caused by these three mechanisms on the sensing kinetics relied on the phase region of Pd hydride during the sensing reaction. Two simple strategies, minimizing the thickness of the PMMA membrane layer and reducing the size of the Pd NPs, were proposed to compensate for retardation of the sensing response.

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.

Miscibility Behavior of Ethylene/Vinyl Acetate and C5 Petroleum Resin by FTIR Imaging

FTIR microscopic imaging was used to investigate the miscibility behavior of ethylene/vinyl acetate copolymer (EVA) and C5 petroleum resin. Images with an area of 500 x 500 microm(2) were collected in the reflection mode. The miscibility was characterized by probing the spatial distribution of the carbonyl group (C=O) of EVA in the whole images. It was found that a 1:1 hot-melt mixture of EVA and C5 resin showed a good miscibility behavior. For two different EVA copolymers, one with 18% vinyl acetate (VAc) content showed a better miscibility behavior than that with 28% VAc content. Our results demonstrated that this method allowed a direct, convenient and nondestructive visualization. This developed technique promises to become a powerful tool for studying the miscibility behavior of composite materials.

Correlation between thermal, optical and morphological properties of heterogeneous blends of poly(3-hexylthiophene) and thermoplastic polyurethane

A correlation between thermal, optical and morphological properties of self-sustained films formed from blends of poly(3-hexylthiophene) (P3HT) and thermoplastic polyurethane (TPU), with 1, 10 and 20 wt% of P3HT in TPU, is established. Images of scanning electron microscopy (SEM) show the formation of domains of P3HT into the TPU matrix, characterizing the blend material as heterogeneous. The heat capacity (C(p)) dependence on P3HT contents was investigated in a large temperature interval. In the region of the TPU glass transition, the difference between the experimental and predicted ΔC(p) values is more pronounced for the 1 wt% case, which strongly suggests that in this case there is a higher influence of the P3HT chains on the TPU matrix. The SEM images for the 1 wt% blended film present the formation of the smallest P3HT domains in the TPU matrix. The relatively high reduction of the PL intensity of the pure electronic transition peak in the 1 wt% blended film, in comparison to the other blended films and also to a pure P3HT film, favours the assumption that the smallest P3HT domains are at the origin of a more structural disordered character. This fact is in agreement with the results obtained by Raman spectroscopy and also by photoluminescence resolved by polarization in stretched self-sustained films, showing an ample correlation between morphological, thermal and optical properties of these blended materials. In addition, the thermoplastic properties of the polyurethane configure very good conditions for tensile drawing of P3HT and other conjugated polymer molecules.