Silver Coated Multi-Functional Liquid Crystalline Elastomer Polymeric Composites as Electro-Responsive and Piezo-Resistive Artificial Muscles.

Liquid Crystalline Elastomers (LCEs) are a class of shape-changing polymers with exceptional mechanical properties and potential as artificial muscles/polymer actuators. In this study, we have developed multifunctional LCE actuators with strain sensing and joule heating responsivity. LCEs were successfully synthesized using the thiol-ene Two-staged Michael Addition Polymerization (TMAP) method. The LCE films were further functionalised via sequential polydopamine (PDA) and silver electroless coating. We found that the PDA coating enabled the anchoring of the Ag particles to the LCE, thereby enabling the electrical conductivity of the Ag-LCEs (<0.1 Ωcm-1). Our studies confirm that the Ag/PDA coated LCEs can sense up to ∼30% strain, sense their own actuation strokes, and actuate at a rate of 1.83%/s whilst lifting a weight ∼50 times its mass in response to a 12 V 2A DC current. This article is protected by copyright. All rights reserved.

Crosslinking Rapidly Cured Epoxy Resin Thermosets: Experimental and Computational Modeling and Simulation Study.

The power of computational modeling and simulation for establishing clear links between materials' intrinsic properties and their atomic structure has more and more increased the demand for reliable and reproducible protocols. Despite this increased demand, no one approach can provide reliable and reproducible outcomes to predict the properties of novel materials, particularly rapidly cured epoxy-resins with additives. This study introduces the first computational modeling and simulation protocol for crosslinking rapidly cured epoxy resin thermosets based on solvate ionic liquid (SIL). The protocol combines several modeling approaches, including quantum mechanics (QMs) and molecular dynamics (MDs). Furthermore, it insightfully provides a wide range of thermo-mechanical, chemical, and mechano-chemical properties, which agree with experimental data.

Upcycling Polystyrene.

Several environmental and techno-economic assessments highlighted the advantage of placing polystyrene-based materials in a circular loop, from production to waste generation to product refabrication, either following the mechanical or thermochemical routes. This review provides an assortment of promising approaches to solving the dilemma of polystyrene waste. With a focus on upcycling technologies available in the last five years, the review first gives an overview of polystyrene, its chemistry, types, forms, and varied applications. This work presents all the stages that involve polystyrene's cycle of life and the properties that make this product, in mixtures with other polymers, command a demand on the market. The features and mechanical performance of the studied materials with their associated images give an idea of the influence of recycling on the structure. Notably, technological assessments of elucidated approaches are also provided. No single approach can be mentioned as effective per se; hybrid technologies appear to possess the highest potential. Finally, this review correlates the amenability of these polystyrene upcycling methodologies to frontier technologies relating to 3D printing, human space habitation, flow chemistry, vertical farming, and green hydrogen, which may be less intuitive to many.

Nanocellulose: A Fundamental Material for Science and Technology Applications.

Recently, considerable interest has been focused on developing greener and biodegradable materials due to growing environmental concerns. Owing to their low cost, biodegradability, and good mechanical properties, plant fibers have substituted synthetic fibers in the preparation of composites. However, the poor interfacial adhesion due to the hydrophilic nature and high-water absorption limits the use of plant fibers as a reinforcing agent in polymer matrices. The hydrophilic nature of the plant fibers can be overcome by chemical treatments. Cellulose the most abundant natural polymer obtained from sources such as plants, wood, and bacteria has gained wider attention these days. Different methods, such as mechanical, chemical, and chemical treatments in combination with mechanical treatments, have been adopted by researchers for the extraction of cellulose from plants, bacteria, algae, etc. Cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), and microcrystalline cellulose (MCC) have been extracted and used for different applications such as food packaging, water purification, drug delivery, and in composites. In this review, updated information on the methods of isolation of nanocellulose, classification, characterization, and application of nanocellulose has been highlighted. The characteristics and the current status of cellulose-based fiber-reinforced polymer composites in the industry have also been discussed in detail.

An ultralight, elastic carbon nanofiber aerogel with efficient energy storage and sorption properties.

The fabrication of ultralight strong carbon nanofiber aerogels with excellent elasticity is still a challenge. Herein, 3D mesoporous graphene/carbon nanofibers (G/CNF) were prepared for the first time from polyacrylonitrile/poly(4-vinyl phenol) (PAN/PVPh) electrospun fibers. Through hydrogen bonding interactions between PAN and PVPh polymer chains, traditional soft carbon nanofibers can be converted to form hard nanofiber aerogels with excellent mechanical, electrical, and sorption properties. The specific interactions among PAN/PVPh led to the formation of porous features on carbonized nanofiber foams. The 3D carbon foams are extremely elastic, strong, and light in weight, and they exhibited super oleophilic and fire-resistance properties. Electrochemical studies indicate that the G/CNF foam achieves a capacitance of up to 267 F g-1 (at a scan rate of 1 mV s-1), with an energy density of 37.04 W h kg-1, exhibiting better electrochemical performance than other reported porous carbon devices. In addition, the G/CNF foam also exhibits sorption capacity towards various organic solvents and oils. This study paves the way toward a new class of lightweight and robust porous carbon nanocomposites for application in electrochemical energy storage systems and oil sorption devices.

Core-Shell Nanofibers of Polyvinylidene Fluoride-based Nanocomposites as Piezoelectric Nanogenerators.

Flexible piezoelectric nanogenerators (PENG) are widely applied to harvest sustainable energy from multiple energy sources. The rational and simple design of PENG have great potential in soft electronics. Here we design a highly flexible PENG using the polyvinylidene fluoride (PVDF) and its copolymer, polyvinylidene hexafluoropropylene (PVDF-HFP) with two nanoarchitectures of semiconducting metal oxides, TiO2 and ZnO. The nanotubes of TiO2 and nanoflowers of ZnO are embedded in these different polymeric media by solvent mixing, and new fiber mats are generated by coaxial electrospinning technique. This process aligns the dipoles of polymers and nanomaterials, which is normally a pre-requisite for higher piezo potential. With excellent mechanical strength and flexibility, the tailored lightweight fiber mats are capable of producing good output voltage (a maximum of 14 V) during different mechanical vibrations at various frequencies and in response to human motions. The hybrid nanocomposite PENG is durable and inexpensive and has possible applications in wearable electronics.

Blood Pressure Sensors: Materials, Fabrication Methods, Performance Evaluations and Future Perspectives.

Advancements in materials science and fabrication techniques have contributed to the significant growing attention to a wide variety of sensors for digital healthcare. While the progress in this area is tremendously impressive, few wearable sensors with the capability of real-time blood pressure monitoring are approved for clinical use. One of the key obstacles in the further development of wearable sensors for medical applications is the lack of comprehensive technical evaluation of sensor materials against the expected clinical performance. Here, we present an extensive review and critical analysis of various materials applied in the design and fabrication of wearable sensors. In our unique transdisciplinary approach, we studied the fundamentals of blood pressure and examined its measuring modalities while focusing on their clinical use and sensing principles to identify material functionalities. Then, we carefully reviewed various categories of functional materials utilized in sensor building blocks allowing for comparative analysis of the performance of a wide range of materials throughout the sensor operational-life cycle. Not only this provides essential data to enhance the materials' properties and optimize their performance, but also, it highlights new perspectives and provides suggestions to develop the next generation pressure sensors for clinical use.

Nanofibrillar micelles and entrapped vesicles from biodegradable block copolymer/polyelectrolyte complexes in aqueous media.

Here we report a viable route to fibrillar micelles and entrapped vesicles in aqueous solutions. Nanofibrillar micelles and entrapped vesicles were prepared from complexes of a biodegradable block copolymer poly(ethylene oxide)-block-poly(lactide) (PEO-b-PLA) and a polyelectrolyte poly(acrylic acid) (PAA) in aqueous media and directly visualized using cryogenic transmission electron microscopy (cryo-TEM). The self-assembly and the morphological changes in the complexes were induced by the addition of PAA/water solution into the PEO-b-PLA in tetrahydrofuran followed by dialysis against water. A variety of morphologies including spherical wormlike and fibrillar micelles, and both unilamellar and entrapped vesicles, were observed, depending on the composition, complementary binding sites of PAA and PEO, and the change in the interfacial energy. Increasing the water content in each [AA]/[EO] ratio led to a morphological transition from spheres to vesicles, displaying both the composition- and dilution-dependent micellar-to-vesicular morphological transitions.

Individual dispersion of carbon nanotubes in epoxy via a novel dispersion-curing approach using ionic liquids.

The effective dispersion of carbon nanotubes (CNTs) in a thermoset was achieved using ionic liquid as the dispersion-curing agent. We preferentially dispersed multiwalled carbon nanotubes (MWCNTs) down to individual tube levels in epoxy resin. Here the dispersion is ruled by the depletion of physical bundles within the MWCNT networks, for which molecular ordering of ionic liquids is considered responsible. The quantitative analyses using ultra small angle X-ray scattering (USAXS) confirmed the dispersion of individual MWCNTs in the matrix. The distance between the dispersed nanotubes was calculated at different nanotube loadings using the power law fitting of the USAXS data. The fine dispersion and subsequent curing, both controlled by ionic liquid, lead to composites with substantially enhanced fracture mechanical and thermomechanical properties with no reduction in thermal properties. Merging processing techniques of nanocomposites with ionic liquid for efficient dispersion of nanotubes and preferential curing of thermosets facilitates the development of new, high performance materials.

A simple and effective approach to vesicles and large compound vesicles via complexation of amphiphilic block copolymer with polyelectrolyte in water.

This work reports for the first time a simple and effective approach to trigger a spheres-to- vesicles morphological transition from amphiphilic block copolymer/polyelectrolyte complexes in aqueous solution. Vesicles and large compound vesicles (LCVs) were prepared via complexation of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) with poly(acrylic acid) (PAA) in water and directly visualized using cryo-TEM. The complexation and morphological transitions were driven by the hydrogen bonding between the complementary binding sites on the PAA and PEO blocks of the block copolymer. The findings in this work suggest that complexation between amphiphilic block copolymer and polyelectrolyte is a viable approach to vesicles and LCVs in aqueous media.

Multiple vesicular morphologies in AB/AC diblock copolymer complexes through hydrogen bonding interactions.

We report for the first time multiple vesicular morphologies in block copolymer complexes formed in aqueous media via hydrogen bonding interactions. A model AB/AC diblock copolymer system consisting of polystyrene-block-poly(acrylic acid) (PS-b-PAA) and polystyrene-block-poly(ethylene oxide) (PS-b-PEO) was examined using transmission electron microscopy, small-angle X-ray scattering, and dynamic light scattering. The complexation and morphological transitions were driven by the hydrogen bonding between the complementary binding sites on PAA and PEO blocks of the two diblock copolymers. Upon the addition of PS-b-PEO, a variety of bilayer aggregates were formed in PS-b-PAA/PS-b-PEO complexes including vesicles, multilamellar vesicles (MLVs), thick-walled vesicles (TWVs), interconnected compound vesicles (ICCVs), and irregular aggregates. Among these aggregates, ICCVs were observed as a new morphology. The morphology of aggregates was correlated with respect to the molar ratio of PEO to PAA. At [EO]/[AA] = 0.5, vesicles were observed, while MLVs were obtained at [EO]/[AA] = 1. TWVs and ICCVs were formed at [EO]/[AA] = 2 and 6, respectively. When [EO]/[AA] reached 8 and above, only irregular aggregates appeared. These findings suggest that complexation between two amphiphilic diblock copolymers is a viable approach to prepare polymer vesicles in aqueous media.

Microphase separation through competitive hydrogen bonding in self-assembled A-b-B/C diblock copolymer/homopolymer complexes.

We present a study of microphase separation induced by competitive hydrogen bonding in A-b-B/C diblock copolymer/homopolymer complexes where the diblock copolymer A-b-B is immiscible and the homopolymer C can interact unequally with both A and B blocks through hydrogen bonding. A model system containing poly(2-vinyl pyridine)-block-poly(methyl methacrylate) (P2VP-b-PMMA) and poly(4-vinyl phenol) (PVPh) in tetrahydrofuran was investigated. In these self-assembled complexes, microphase separation takes place due to the disparity in intermolecular interactions. Specifically, PVPh and P2VP blocks interact strongly to form complex, whereas PVPh and PMMA blocks interact weakly. The hydrogen bonding interactions were revealed by infrared spectroscopy and analyzed in terms of the difference in interassociation constants (K), i.e., interaction parameters of each blocks of the block copolymer to the homopolymer and according to the random phase approximation. The phase behavior of the complexes was investigated with small-angle x-ray scattering and transmission electron microscopy. A series of morphologies including lamellae, hexagonal cylinders, wormlike microdomains, and hierarchical structures was documented as a function of the copolymer concentration. Moreover, we outlined how hydrogen bonding determines the self-assembly and causes morphological transitions in different A-b-B/C diblock copolymer/homopolymer systems with respect to the K values.