Solid Polymeric Materials Research Articles

Development and Characterization of Polymeric-based Biomaterial from Agro-food Waste: A Sustainable and Eco-friendly Approach Towards Plastic Pollution

Commercial plastics are potentially hazardous and can be carcinogenic due to the incorporation of chemical additives along with other additional components utilized as brominated flame retardants and phthalate plasticizers during production that excessively produce large numbers of gases, litter, and toxic components resulting in environmental pollution. Biodegradable plastic derived from natural renewable resources is the novel, alternative, and innovative approach considered to be potentially safe as a substitute for traditional synthetic plastic as they decompose easily without causing any harm to the ecosystem and natural habitat. The utilization of undervalued compounds, such as by-products of fruits and vegetables in the production of biodegradable packaging films, is currently a matter of interest because of their accessibility, affordability, ample supply, nontoxicity, physiochemical and nutritional properties. Industrial food waste was processed under controlled conditions with appropriate plasticizers to extract polymeric materials. Biodegradability, solubility, and air test analysis were performed to examine the physical properties of polymers prior to the characterization of the biofilm by Fourier-transformed infrared spectroscopy (FTIR) for the determination of polymeric characteristics. The loss of mass examined in each bioplastic film was in the range of 0.01g to 0.20g. The dimension of each bioplastic was recorded in the range of 4.6 mm to 28.7 mm. The existence of -OH, C=C, C=O stretching, and other crucial functional groups that aid in the creation of a solid polymeric material are confirmed by FTIR analysis. This study provides an alternative approach for sustainable and commercially value-added production of polymeric-based biomaterials from agro-industrial waste as they are rich in starch, cellulose, and pectin for the development of bio-plastics. The rationale of this project is to achieve a straightforward, economical, and durable method for the production of bio-plastics through effective utilization of industrial and commercial fruit waste, ultimately aiding in revenue generation.

Intermediate Color Emission via Nanographenes with Organic Fluorophores

AbstractPhotoluminescence (PL) color can be tuned by mixing fluorophores emitting the three primary colors in an appropriate ratio. When color tuning is achieved on a single substrate, we can simplify device structures. We demonstrated that nanographenes (NGs), which are graphene fragments with a size of tens of nanometers, could be utilized as carriers of fluorophores. The addition of red‐ and blue‐light‐emitting fluorophores on the edge successfully reproduced the purple light. The relative PL intensities of the fluorophores could be regulated by the excitation wavelength, enabling multicolor emission between blue and red light. Owing to the triphenylamine units of the fluorophores, the NGs showed PL enhancement due to aggregation. This characteristic was valuable for the fabrication of solid polymer materials. Specifically, the functionalized NGs can be dispersed into polyvinylidene difluoride. The resultant polymer films emitted red, blue, and purple color. Our study demonstrated the potential applicability of NGs for fluorophore carriers capable of reproducing intermediate colors of light.

Intermediate Color Emission via Nanographenes with Organic Fluorophores.

Photoluminescence (PL) color can be tuned by mixing fluorophores emitting the three primary colors in an appropriate ratio. When color tuning is achieved on a single substrate, we can simplify device structures. We demonstrated that nanographenes (NGs), which are graphene fragments with a size of tens of nanometers, could be utilized as carriers of fluorophores. The addition of red- and blue-light-emitting fluorophores on the edge successfully reproduced the purple light. The relative PL intensities of the fluorophores could be regulated by the excitation wavelength, enabling multicolor emission between blue and red light. Owing to the triphenylamine units of the fluorophores, the NGs showed PL enhancement due to aggregation. This characteristic was valuable for the fabrication of solid polymer materials. Specifically, the functionalized NGs can be dispersed into polyvinylidene difluoride. The resultant polymer films emitted red, blue, and purple color. Our study demonstrated the potential applicability of NGs for fluorophore carriers capable of reproducing intermediate colors of light.

Naphthopyrans as efficient dual color photoinitiators for volumetric 3D printing

By combining photochromic naphthopyran with a Norrish-type II benzophenone photoinitiator, a new photoswitchable photoinitiator was created that is activated by the successive absorption of two different wavelengths. This dual-colour photoinitiator was used to prepare various thin solid polymeric materials using UV and visible light LED to promote the formation of radicals that initiate polymerization of an acrylate monomer. The use of this system ensures that only the areas that receive double irradiation polymerize, providing a simple way to control polymerization using only light.

One-pot ternary sequential reactions for photopatterned gradient multimaterials

One-pot ternary sequential reactions for photopatterned gradient multimaterials

Effect of Tannins Addition on Thermal Stability of Furfurylated Wood.

This article presents the effect of the addition of condensed tannins, used as a reticulation agent, on the polymerization of furfuryl alcohol during wood furfurylation, as well as the effect of these condensed tannins on the thermal stability of modified wood. Three kinds of dicarboxylic acids (adipic acid, succinic acid, and tartaric acid), as well as glyoxal, used as model of a wood reticulation agent, were used to catalyze the polymerization of furfuryl alcohol or tannin-furfuryl alcohol solutions. Impregnation of furfuryl alcohol or tannin-furfuryl alcohol solution into the wood, followed by curing at 103 °C for a specific duration, was performed for the wood modification. The thermal stability of the obtained tannin-furfuryl alcohol polymers and their corresponding modified woods was investigated. The leaching resistance and dimensional stability of the modified woods were also evaluated. Results indicated that the partial substitution of furfuryl alcohol by the tannins improved the polymerization reactivity in conditions where furfuryl alcohol alone did not lead to the formation of a solid polymeric material. The thermal stability and leaching resistance of the furfurylated wood in the presence of tannins were improved. Dimensional stability was also improved for furfurylated samples, but the effect of tannin addition was not so obvious, depending on the acidic catalyst used.

An Air- and Moisture-stable Zinc(II) Carbene Dithiolate Dimer Showing Fast Thermally Activated Delayed Fluorescence and Dexter Energy Transfer Catalysis.

A dimeric ZnII carbene complex featuring bridging and chelating benzene-1,2-dithiolate ligands is highly stable towards air and water. The donor-Zn-acceptor structure leads to visible light emission in the solid state, solution and polymer matrices with λmax between 577-657 nm and, for zinc(II) complexes, unusually high radiative rate constants for triplet exciton decay of up to kr =1.5×105 s-1 at room temperature. Variable temperature and DFT/MRCI studies show that a small energy gap between the 1/3 LL/LMCT states of only 79 meV is responsible for efficient thermally activated delayed fluorescence (TADF). Time-resolved luminescence and transient absorption studies confirm the occurrence of long-lived, dominantly ligand-to-ligand charge transfer excited states in solution, allowing for application in Dexter energy transfer photocatalysis.

Investigation of elastic properties of solid polymer materials by indentation method

The mechanical properties of solid (crystalline) polymer materials are proposed to be investigated simultaneously using two complementary methods based on controlled indentation of a spherical indenter. The first method consists in the direct analysis of the load curve without using the concept of contact stiffness; the second method is based on measurements of the size of prints depending on the magnitude of the static load. The study shows that the reinforcement of a solid polymer with carbon fibers can lead to a significant increase in its elastic-strength properties. Keywords: polymer composite materials, indentation, Hertz contact theory, spherical stamp, reduced modulus of elasticity, Brinell hardness, ultimate strength.

Исследование упругих свойств твердых полимерных материалов методом индентирования

The mechanical properties of solid (crystalline) polymer materials are proposed to be investigated simultaneously using two complementary methods based on controlled indentation of a spherical indenter. The first method consists in the direct analysis of the load curve without using the concept of contact stiffness; the second method is based on measurements of the size of prints depending on the magnitude of the static load. The study shows that the reinforcement of a solid polymer with carbon fibers can lead to a significant increase in its elastic-strength properties.

Исследование упругих свойств полиэфирэфиркетона методом одноосного сжатия

The mechanical properties of polyetheretherketone, which has a partially crystalline structure, were studied using the low-speed uniaxial compression method. Compression diagrams were measured, from which the elastic and elastoplastic properties of the material were characterized. Compression experiments are applicable to selecting the mode of cold gas-dynamic spraying of solid polymer materials.

Effect of segmental motion on hydrolytic degradation of polyglycolide in electro-spun fiber mats.

Recently, environmentally degradable polymers have received great attention from the perspective of sustaining the aquatic environment. To control the degradation behavior of solid polymer materials in an aqueous phase, it is crucial to better understand the thermal molecular motion of polymer chains in water. We herein focus on polyglycolide (PGA), which is one of the representative aliphatic polyesters that are hydrolytically degradable. Three kinds of fiber mats of PGA with different fiber diameters and comparable crystallinities were prepared using an electrospinning method. Our choice of fiber mats was because the ratio of the surface area, where the hydrolytic degradation starts to occur, to the volume was larger than that for the films. Dynamic mechanical analysis (DMA) enabled us to gain direct access to the dynamic glass transition temperature (Tgα) of PGA in the fiber mats both in dry gaseous nitrogen and liquid water. The Tgα value varied not only with the presence of water molecules, but also with the fiber diameter, or the specific surface area. The degradation behavior of PGA fiber mats was examined by immersing the samples in phosphate-buffered saline at various temperatures. When the segmental motion of PGA in the fiber mats was released, the apparent crystallinity of the mats increased, meaning that PGA amorphous chains were cleaved and thus partially eluted into the aqueous phase. It was also shown that partially cleaved chains crystallized.

Photocycloadditions for the Design of Reversible Photopolymerizations

The quest for circular designs and ways to reuse polymer materials demands further advances in the development of reversible chemistries. Stimuli-responsive systems incorporated into polymer materials that enable the formation and cleavage of covalent bonds, hold great potential to reversibly decompose materials into their original building blocks. [2π+2π] photocycloadditions, for which the addition and reversion mechanism can be triggered by disparate wavelengths, stand as an attractive platform for triggering such controlled and reversible photoligation towards achieving renewable polymer materials. This perspective highlights the potential of this type of photochemistry to incorporate solid polymer materials and generate reversible polymerizations. The design of effective photoresponsive materials with specific functions requires the consideration of a number of parameters. Following a bottom-up approach – from molecular chemistry to macromolecular functionality – this perspective provides a recipe of the key aspects to consider in the design of such advanced renewable materials. Furthermore, examples of the state of the art in the field are highlighted and an overview of the fundamental challenges that remain is provided. Finally, an outlook on the next frontiers to cross is proposed.

Investigation of Dry Sliding Friction Wear Behavior of CuSn11 Bronze Plain Bearing Applying Impregnated Graphite-Filled PTFE

Self-lubricating bearings are produced by using copper-based materials and solid lubricating polymer materials, which are widely used in industrial applications. Self-lubricating bearings have been developed to improve systems that do not have the possibility of continuous lubrication. This study describes the experimental investigation of tribological properties of graphite-filled polytetrafluoroethylene (PTFE) composites. First, the CuSn11 porous specimens were produced by powder metallurgy. The superior properties of bronze and PTFE were used to create the composite specimens. Solid lubricants, namely, pure PTFE and two different graphite-filled PTFE (PTFE + 10 wt% graphite and PTFE + 20 wt% graphite) mixtures were impregnated into pores of the bronze specimens using a spray coating method. Thus, bronze composite specimens with graphite-filled PTFE were obtained. Then changes in the friction coefficient and wear loss were achieved differently under three loads and sliding speeds with wear tests performed under dry test conditions. The results showed that the graphite additive reduced the friction coefficient and the wear loss. The lowest friction coefficient was obtained from the 20 wt% graphite-filled specimen under the lowest sliding distance (4500 m) and the highest load (70 N) test conditions. However, a 2.95% reduction in the friction coefficient and 16.28% reduction in the wear loss of PTFE + 10 wt% graphite specimen were detected compared to the 20 wt% graphite specimen, depending on the increase in sliding distance under the highest sliding distance (13,500 m) and the highest applied load (70 N) test conditions.

A Perspective on the Force-Induced Heterolytic Bond Cleavage in Triarylmethane Mechanophores

AbstractTriarylmethane derivatives and their corresponding trityl carbocations are among the oldest chemical species synthesized and studied by chemists. The carbocationic platforms are particularly interesting due to their stability, high extinction coefficient, and tunable absorption of light in the visible spectrum, which can be achieved through structural modifications. These stable cations are traditionally obtained through heterolytic cleavage of judiciously designed, parent triarylmethanes by exposure to acids or UV light (λ < 300 nm), and methods based on electrochemistry or radiolysis. Our group has recently discovered that trityl carbocations can be generated also via mechanical stimulation of solid polymer materials featuring triarylmethane units as covalent crosslinks. In this Synpacts contribution, we expand on our previous finding by discussing some intriguing research questions that we aim to tackle in the immediate future.1 Introduction2 The Development of Our First Triarylmethane Mechanophore3 The Potential Reversibility of Triarylmethane Mechanophores4 A General Molecular Platform for Force-Induced, Scissile, Homolytic and Heterolytic Bond Cleavage?5 Conclusion

Chemically Recyclable CO2 -Based Solid Polyesters with Facile Property Tunability.

Synthesizing chemically recyclable solid polymeric materials is a significant strategy to potentially achieve carbon neutral production of new polymers and alleviate plastic pollution, especially when the synthesis is based on CO2 and inexpensive co-feedstocks available in large scales. Additionally, polymeric materials should have high enough molecular weight to exhibit distinguished properties from low molar mass polymers to serve for a broader range of application scenarios. However, up to now, strategies for developing solid-state CO2 -based chemically recyclable polyesters with both high molecular weight and facile property tunability are still unprecedented. Herein, a brand-new synthetic route is developed to synthesize chemically recyclable CO2 -based solid polyesters with high molecular weight (Mn up to 587.7kg mol-1 ) and narrow dispersity (Đ <1.2), which should further broaden the potential application scenarios of new CO2 -based polyesters. Additionally, complete monomer recovery from poly(δLH2 ) material is also achieved. The preserved terminal alkene groups allow facile property tuning of the polyesters via photo-initiated thiol-ene click reactions, enabling more potential utilities and further functionalizations.

Donor–Acceptor Stenhouse Adduct‐Polydimethylsiloxane‐Conjugates for Enhanced Photoswitching in Bulk Polymers

Donor-acceptor Stenhouse adducts (DASAs) are a rapidly emerging class of visible light-activated photochromes and DASA-functionalized polymers hold great promise as biocompatible photoresponsive materials. However, the photoswitching performance of DASAs in solid polymer matrices is often low, particularly in materials below their glass transition temperature. To overcome this limitation, DASAs are conjugated to polydimethylsiloxanes which have a glass transition temperature far below room temperature and which can create a mobile molecular environment around the DASAs for achieving more solution-like photoswitching kinetics in bulk polymers. The dispersion of DASAs conjugated to such flexible oligomers into solid polymer matrices allows for more effective and tunable DASA photoswitching in stiff polymers, such as poly(methyl methacrylate), without requiring modifications of the matrix. The photoswitching of conjugates with varying polymer molecular weight, linker type, and architecture is characterized via time-dependent UV-vis spectroscopy in organic solvents and blended into polymethacrylate films. In addition, DASA-functionalized polydimethylsiloxane networks, accessible via the same synthetic route, provide an alternative solution for achieving fast and efficient DASA photoswitching in the bulk owing to their intrinsic softness and flexibility. These findings may contribute to the development of DASA-functionalized materials with better tunable, more effective, and more reversible modulation of their optical properties.

Пожарная опасность светодиодных осветительных систем в условиях обитаемых гермоотсеков космических летательных аппаратов

Представлены результаты оценки пожарной опасности светодиодных осветительных систем в условиях обитаемых гермоотсеков космических летательных аппаратов (КЛА). Проведен анализ этих систем с учетом влияния обогащения атмосферы кислородом, а также особенностей их конструкционного исполнения. Показана перспектива пожаробезопасного использования светодиодных осветительных систем для освещения и сигнализации в условиях обитаемых гермоотсеков КЛА и даны рекомендации по обеспечению пожарной безопасности светодиодных осветительных систем. When operating the habitable hermetic compartments of spacecrafts there is a need for high-quality illumination of the hermetic compartment for astronauts’ activities. It is also required to use light sources to indicate the operating modes of the equipment. Previously occurring fire-hazardous situations in the habitable hermetic compartments of manned spacecrafts caused the need to put fire hazard of these products among the main hazards of space flight. Currently, LEDs, which are semiconductor elements, are widely used as sources of optical radiation. They began to be used in space engineering not only as lamps, but also for other purposes. LED lamps have a significant advantage over all alternative options. They have longer service life, high lamp efficiency, reduced heat generation, high vibration resistance, low weight. At the same time, in LED lighting systems there are used highly flammable polymer materials, in particular polypropylene, which is one of the most flammable polymer materials in the air environment. In the oxygen-rich atmosphere of hermetic compartments the fire risk in any electrical equipment increases due to a significant decrease of the self-ignition temperature and the ignition energy of polymer materials with the oxygen concentration increase in the atmosphere. The paper analyzes fire hazard of LED lighting systems used as illumination in the command compartment of a manned transport space vehicle (MTSV). The analysis was carried out taking into account the influence of oxygen enrichment of the atmosphere, as well as taking into account the design features of LED lighting systems for use in the habitable hermetic compartments of spacecrafts. The analysis of the lamp showed that solid and liquid polymeric materials are the only combustible substances in their design.

Simultaneous Measurement of Temperature and Relative Humidity Using Cascaded C-shaped Fabry-Perot interferometers

In this paper, a novel platform for simultaneous measurement of relative humidity (RH) and temperature using dual Fabry&#x2013;Perot interferometers (FPIs) based on C-shaped fiber was demonstrated. The sensor was composed by splicing two sections of C-shaped fiber between single mode fiber (SMF). Polydimethylsiloxane (PDMS) and polyvinyl alcohol (PVA) are filled in the two sections of C-shaped fibers to increase sensitivity to temperature and RH. This is the first demonstration that solid polymer materials can be added to the C-shaped fiber interferometers for sensing. In our experiment, RH sensitivities of -0.128 nm&#x002F;&#x0025;RH and 0.038 nm&#x002F;&#x0025;RH in the range of 20&#x0025;RH to 45&#x0025;RH, and temperature sensitivities of 0.022 nm&#x002F;&#x00B0;C and -0.722 nm&#x002F;&#x00B0;C in the temperature range of 15 &#x00B0;C to 45&#x00B0;C, were acquired for dual FPIs, respectively. We verified that it is possible to use the sensitivity matrix method to measure two parameters simultaneously. In addition, it has the benefits of simple structure, excellent stability and high sensitivity, and has a broad application prospect in agriculture, food processing and environmental measurement.

Chemically recyclable polyesters from CO2, H2, and 1,3-butadiene

Chemically recyclable solid polymeric materials with commercializable properties only using CO2 and inexpensive bulk chemicals as chemical feedstock can open a brand-new avenue to economically viable, large-scale fixation of CO2 over a long period of time. Despite previous great advancements, development of such a kind of CO2-based polymers remains a long-term unsolved research challenge of great significance. Herein, we reported the first methodology to polymerize six-membered lactone with two substituents vicinal to the ester group (HL), a compound previously found to be non-polymerizable. The present methodology enables the first synthesis of chemically recyclable solid polyesters (polyHL) with a high CO2 content (28 wt %) and large molecular weights (Mn up to 613.8 kg mol−1). Transparent membranes with promising pressure-sensitive adhesive (PSA) properties comparable with their commercial counterparts can be conveniently fabricated from the polyesters. Mechanistic studies indicate that rigorous removal of water impurity is the key to the successful polymerization of the relatively inert disubstituted six-membered lactone. A complete monomer recovery from polyHL was also successfully achieved under mild catalytic conditions. The synthesis of polyHL only requires CO2 and two inexpensive bulk chemicals, H2 and 1,3-butadiene, as the starting materials, thus providing a new strategy for potential scalable chemical utilization of CO2 with desirable economic values and concomitant mitigation of CO2 emissions. This work should inspire future research to make useful new solid CO2-based polymers that can meaningfully increase the scale of chemical utilization of CO2 and promote the contribution of chemical utilization of CO2 to global mitigation of CO2 emissions.

Biophysical Properties of Foamed and Solid Polymers Used in Orthotics and Prosthetics.

Orthotic and prosthetic materials should have good mechanical and antibacterial properties. Therefore, in our study, we consider four common foamed closed-cells and two solid polymeric materials regarding their mechanical behaviour and tendency for bacterial adhesion. For all materials, the surface roughness, hydrophobicity, zeta potential, tensile properties, hardness and CIE color parameters were measured. We found that foamed polymeric materials have higher roughness, higher hydrophobicity, lower Young’s modulus, lower maximum tensile strength and lower hardness than solid materials. Bacterial adhesion test measurements based on observation by scanning electron microscopy show much a lower adhesion extent of S. aureus on solid materials than on foamed materials. The measured biophysical properties could be the key data for users to select the optimal materials.