Polar Polymers Research Articles

Molecular Dynamics Investigation of the Pressure Dependence of Glass Formation in a Charged Polymer Melt

Most commodity polymers are derived from petroleum raw materials, and correspondingly, these materials are normally uncharged and nonpolar, attributes that make this class of material relatively insoluble in water and relatively slow to breakdown in the environment. Natural and synthetic charged polymer materials often do not exhibit these drawbacks, thereby offering the potential for being more sustainable. As with all polymer materials, properties related to glass formation play a central role in the design and characterization of materials. Here, we investigate the influence of a crucial processing variable, the pressure P, on the glass formation of a coarse-grained charged polymer melt using molecular dynamics simulation. We find that the temperature (T) dependence of the thermodynamics and segmental dynamics under variable P conditions largely resemble the trends observed before for uncharged polymer liquids. In particular, we are able to organize all our segmental relaxation data as functions of both T and P in terms of the conventional phenomenology for uncharged polymer melts, namely, the Vogel–Fulcher–Tammannn temperature dependence of the structural relaxation time τα and a pressure analog of this equation, etc. Moreover, we can quantitatively describe all our simulation data for both charged and uncharged polymer melts with the string model of glass formation. Importantly, our results indicate that the main effect of charge on the dynamics of polymeric glass-forming liquids is to “renormalize” the cohesive interaction strength. This opens the possibility of applying theories of neutral polymer melts to describe the glass formation of synthetic and natural charged polymer melts, ionic fluids, and possibly even polar polymer melts, once an accounting is made for how charge modifies the effective cohesive interaction strength.

An Integrated Plasma-Photocatalytic System for Upcycling of Polyolefin Plastics.

Nondegradable polyolefin plastics, which account for >60 % of total plastic waste, trigger severe global concerns and thus demand effective management technologies. However, owing to the chemical inertness of non-polar C-C backbones in the polyolefin structure, efficient upcycling of polyolefin plastics under ambient conditions remains a great challenge. This study introduces an integrated plasma-photocatalytic technology, coupling plasma treatment with solar-driven reforming under mild conditions, for the efficient upcycling of polyolefin plastics into value-added hydrogen and gaseous fuels. The first plasma step grafts oxygenated groups, such as -OH, O-C=O, and C=O, onto the polyolefin chains, which leads to the formation of a polar and hydrophilic polymer that facilitates the subsequent reforming in the photocatalytic step. Therefore, high hydrogen production activity with a benchmark efficiency of >100 μmol g-1 h-1 was achieved. Moreover, the integrated process also demonstrates high versatility in upcycling different polyolefin plastics including polyethylene, polypropylene and polyvinyl chloride. The findings provide a new avenue for plastic upcycling in an efficient and sustainable way.

High‐damping ultralow−gel nonpolar elastomeric polymer through thiol−ene photo−click chemistry reaction

AbstractWith the increasing demand for high‐performance damping rubber material in various fields, improving the damping performance of existing nonpolar rubber has garnered tremendous scientific and industrial interest. However, it remains a long‐standing challenge to improve the damping properties of nonpolar rubber materials due to their low intrinsic glass transition temperature (Tg) and incompatible surface energy with high‐damping polar polymers or fillers. To solve this conundrum, ultra‐low gel multifunctional carboxy‐functional high vinyl polybutadiene HVBR (HVBR/COOH‐x%) was prepared by grafting 3‐mercaptopropionic acid (3PMA) onto HVBR via thiol−ene photo−click. The effects of reaction parameters including molecular weight, 1,2‐vinyl content, photoinitiators, reaction time, thiol and photoinitiator dosage on gel content and carboxyl grafting ratio were investigated. The HVBR/COOH‐x% demonstrate a controllable grafting ratio range from 2% to 73%. Furthermore, the increased Tg and intermolecular force resulted in excellent performance, including high‐glass transition temperature of 26.3°C, tensile strength of 15.52 MPa, and elongation at break of 396.16%. Particularly with a wide range of effective damping temperatures above 46.6°C. Meanwhile, COOH endowed the HVBR with better self‐viscosity, but also equipped it with stronger mutual viscosity. Therefore, this experiment proposes a feasible path to high damping and high adhesion in nonpolar rubber materials.

Creating Ultrahigh and Long‐Persistent Triboelectric Charge Density on Weak Polar Polymer via Quenching Polarization

AbstractTo achieve high charge density for the triboelectric polymer is a crucial task for fabricating triboelectric nanogenerators (TENGs). This work has developed a quenching polarization (QP) method to create ultrahigh and long‐persistent triboelectric charge on the triboelectric polymer with weak dipole polarity. The Ethylene chlorotrifluoroethylene copolymer (ECTFE) film can reach a charge density of 391 µC m−2 in the vertical contact mode by using this QP treatment, which is 200% higher than the result achieved by the most widely used method of corona polarization. The mechanism of the improvement through QP on the triboelectric properties is studied on the basis of the polarization induced grain refinement and interfacial trapping. The QP‐treated ECTFE can maintain ultra‐high charge density for both solid‐solid and solid‐liquid TENG. More interestingly, the charge induced by QP treatment is so persistent that it produces a recoverable discharging phenomenon for solid‐liquid TENG, which has never been observed before. This QP method provides a different approach for fabricating high‐performance triboelectric materials, while the QP‐induced changes in crystallization and tribo‐charge density can help to complete the physical understanding of the electrification mechanism of triboelectric polymer.

Investigations of Band Alignment at Interfaces of Au/Polypropylene and Au/Polyimide

As charge injection from metal into dielectric polymer causes degradation and breakdown of electronic and power devices, the band alignment at the metal/polymer interface should be revealed. To investigate the dominant factors of the band alignment at the metal/polymer interface, we carried out a combined experimental and first-principles computational study. We examined Au/polypropylene (PP) interface and Au/polyimide (PI) interface. PP and PI were chosen as a model system for nonpolar and polar polymers, respectively. The results imply that the band alignment can be determined under the assumption that vacuum levels of metal and polymer match at the interface regardless of the dipole moment of polymers.

Using the method of calculating the total molar energy of cohesion to choose the most effective plasticizer

It is known that products made of polar, crystallized, and high-strength polymers (polyamides, polyesters, cellulose triacetate, polyvinyl chloride, etc.) lose their initial properties that reduce reliability and durability in the process of operation and even during long-term storage due to the increase in internal stresses in them caused by crystallization processes over time. To reduce the impact of such processes on the properties of polymer products, special substances are introduced into their composition, plasticizers, the selection of which is usually carried out empirically, which is not always successful. We proposed in this study to use the ratio of the calculated total molar volumetric energy of cohesion of the compound (the cumulative interaction of interatomic and intermolecular forces in the composition of the compound) to its molecular weight as the specific mass total energy of cohesion, which can be compared with a similar indicator for a plasticizing polymer. The use of such an approach makes it possible to purposefully, even before experimental verification, evaluate the suitability of using this or that compound, oligomer, or polymer as a plasticizer (or modifier), or develop a molecular structure of a new, necessary compound with the inclusion of certain groups in its composition for the purpose of further use as a plasticizer or modifier. In addition, there is an opportunity to monitor the influence of individual structural components of a new compound, oligomer or polymer, its molecular weight, side substituents and their nature on the value of the specific mass total energy of cohesion, as well as to reduce the time for performing research works in this direction and expenses for their implementation.

TSD investigation of P(VDF-TeFE)/Si composites under the gamma irradiation

In the presented work, the charge state of P(VDF-TeFE)/Si-based composites obtained on the basis of nano-Si with a size of 50[Formula: see text]nm and micro-Si particles with a size of 50[Formula: see text][Formula: see text]m and P(VDF-TeFE) copolymer of polyvinylidenefluoride with tetrafluoroethylene from polar polymers, was investigated, the amount of filler and the effect of ionizing radiation on these properties were studied. It has been shown that the observed differences in the charge state parameters of P(VDF-TeFE)/Si composites obtained with nano- and micro-sized Si are due to the higher concentration of nanoparticles and, accordingly, the effective surface area in the composites obtained with nanosized Si, and the change in the mobility of relaxors due to the effects of construction and destruction processes that occur in the polymer matrix and at the interphase boundary after the effect of gamma radiation. The reason for the observed changes in the depolarization processes of polarized P(VDF-TeFE)/nano-Si composites after gamma radiation is the change in the ratio between the construction and destruction processes in the system.

Binder‐Induced Ultrathin SEI for Defect‐Passivated Hard Carbon Enables Highly Reversible Sodium‐Ion Storage

AbstractHard carbon is one of the most promosing anodes for resource‐rich sodium‐ion batteries. However, an unsatisfactory solid–electrolyte‐interphase formed by irreversible electrolyte consumption caused by defects or oxygen‐containing functional groups of hard carbon impedes its further application. Herein, a novel composite binder that is composed of polar polymer chondroitin sulfate A (sodium salt) and polyethylene oxide by hydrogen bonding demonstrates defect passivation capability. This composite binder can reduce the exposure of defects by forming hydrogen bonds with oxygen functional groups on the hard carbon surface and inhibit the decomposition of electrolyte confirmed by in situ differential electrochemical mass spectrometry. In situ Raman and theoretical calculations reveal that multiple polar functional groups in chondroitin sulfate A (sodium salt) can accelerate the transport of Na+ by adsorbing and facilitate the decomposition of PF6− to form NaF. Additionally, polyethylene oxide in the composite binder can increase viscosity and accelerate the transport of Na+. As a result, an ultra‐thin (9 nm, cyro‐TEM) and NaF‐rich solid–electrolyte interphase is obtained, thereby the hard carbon anode achieves improved initial Coulombic efficiency (84%) and high‐capacity retention of 94% after 150 cycles in a NaPF6/ethylene carbonate/dimethyl carbonate electrolyte.

Microplastic pollution in the sediments of interconnected lakebed, seabed, and seashore aquatic environments: polymer-specific total mass through the multianalytical “PISA” procedure

The total mass of individual synthetic polymers present as microplastic (MP < 2 mm) pollutants in the sediments of interconnected aquatic environments was determined adopting the Polymer Identification and Specific Analysis (PISA) procedure. The investigated area includes a coastal lakebed (Massaciuccoli), a coastal seabed (Serchio River estuarine), and a sandy beach (Lecciona), all within a natural park area in Tuscany (Italy). Polyolefins, poly(styrene) (PS), poly(vinyl chloride) (PVC), polycarbonate (PC), poly(ethylene terephthalate) (PET), and the polyamides poly(caprolactame) (Nylon 6) and poly(hexamethylene adipamide) (Nylon 6,6) were fractionated and quantified through a sequence of selective solvent extractions followed by either analytical pyrolysis or reversed-phase HPLC analysis of the products of hydrolytic depolymerizations under acidic and alkaline conditions. The highest concentrations of polyolefins (highly degraded, up to 864 µg/kg of dry sediment) and PS (up to 1138 µg/kg) MPs were found in the beach dune sector, where larger plastic debris are not removed by the cyclic swash action and are thus prone to further aging and fragmentation. Surprisingly, low concentrations of less degraded polyolefins (around 30 µg/kg) were found throughout the transect zones of the beach. Positive correlation was found between polar polymers (PVC, PC) and phthalates, most likely absorbed from polluted environments. PET and nylons above their respective LOQ values were found in the lakebed and estuarine seabed hot spots. The pollution levels suggest a significant contribution from riverine and canalized surface waters collecting urban (treated) wastewaters and waters from Serchio River and the much larger Arno River aquifers, characterized by a high anthropogenic pressure.Graphical abstract

Dipole doping effect in MoS2 field effect transistors based on phase transition of ferroelectric polymer dopant

Molybdenum disulfide (MoS2) has great potential for next-generation electronic devices. On the other hand, stable doping methods are required to adjust its physical properties so MoS2 can be utilized in practical applications, such as transistors and photodetectors. On the other hand, a conventional doping method based on ion implantation is incompatible with 2D MoS2 because of the damage to the lattice structures of MoS2. This paper presents an n-type doping method for MoS2 field-effect transistors (FETs) using a poly (vinylidene fluoride-co-trifluoroethylene) (P (VDF-TrFE)) and polar polymer. The dipole moment of P (VDF-TrFE) provides n-type doping on MoS2 FETs. The polar phase formation in dopant films enhances the doping effects, and the relationship between phase transition and n-type doping states was investigated using optical and electrical characterization methods. Under the optimal doping conditions, the doped MoS2 FET achieved an improved field effect mobility of 34.4 cm2 V−1s–1, a negative shift in the threshold voltage by −25.6 V, and a high on-current of 21 μA compared to the pristine MoS2 FET.

Mechanism of the Polysiloxane Concentration-Dependent Hydrophobicity in Epoxy Resin Based on a Thermodynamic Ring Model With Saturation Effect

To deeply understand the controversial results about nonpolar organics concentration-dependent hydrophobicity in polar polymers, we establish a thermodynamic ring model combined with the saturation effect of surface tension for a smooth multiphase surface. It is found that the static contact angle of the water droplet on the smooth solid surface is significantly affected by the area proportion of nonpolar dispersed phases near the three-phase contact line. The proportion of the nonpolar dispersed phase on the surface is affected by the concentration of the nonpolar dispersed phase and the particle size of the dispersed phase. Due to the high concentration and large particle size of the dispersed phase, the proportion of the nonpolar dispersed phase on the surface has obvious dispersibility, which may lead to the increase or decrease of the proportion of the nonpolar dispersed phase on the surface. When the proportion of the surface nonpolar dispersed phase is low, the static contact angle increases with the increase of the proportion of the surface nonpolar dispersed phase. However, the further increase of the proportion of nonpolar dispersed phase enhances the saturation effect of surface tension, contributing to a saturated static contact angle. Our findings afford a thorough explanation for the reported discordant results about the effect of nonpolar organics concentration on hydrophobicity in polar polymers, which is critical to rational design for polar polymers modified by nonpolar organics.

Photoelectret effect in polymer-AIIBVI (CdS, ZnS) composites of photosensitive semiconductors

The photoelectret effect in composite heterostructures consisting of polar (fluorinecontaining) and non-polar (polyolefins) polymers - high density polyethylene (HDPE), low density polyethylene (LDPE), F42, F2-ME and the inorganic phase AııBvı (CdS, ZnS) has been studied. It has been established that the difference in photoelectret potentials in a given volume share of the inorganic phase mainly depends on the polarity of the polymer matrix. A possible mechanism of the photoelectret effect formed under the combined action of a strong electric field and light in these composites. It has been experimentally established that the potential barrier formed at the polymer- AııBvı semiconductor interface separates the electric charge carriers formed as a result of the internal photoelectric effect and ensures the formation of an electret potential difference. The electret charge state of polymer- AııBvı composites was studied using the spectrum of thermally stimulated current.

A facile strategy to achieve room‐temperature organic long afterglow from melt processible, new two‐dimensional polyamide doped γ‐polyamide 6

AbstractOrganic long afterglow materials can be incorporated into commercial polar polymer in very small amount to significantly reduce cost for application, while gaining excellent mechanical deformability attractively. Their luminescence can be usually enhanced, as the polar polymer can block oxygen diffusion and inhibit inclusion aggregation. However, due to thermal instability of most afterglow materials at high temperature, it is still a great challenge when they are applied for widely used polymer melt in material industry. Herein we report a new afterglow material of doped polymer system by blending a new luminescent, two‐dimensional polyamide sheet (TIB‐3CPBA‐TAPA) with a high‐temperature polyamide 6 (γPA6) melt. The excellent thermal stability of TIB‐3CPBA‐TAPA results from the amide bond‐linked, imidazolium salted and conjugated structure. Interestingly, TIB‐3CPBA‐TAPA/γPA6 is found to emit greenish afterglow luminescence that can last for 4 s at room temperature, only under a loading of 0.1 wt% that harvests the UV exposure efficiently. Different from converting non‐afterglow γ crystal (γPA) into afterglow α crystal (αPA), our facile strategy achieves longer afterglow with a higher melting point (220°C) and a tripled quantum yield (1.8%). In addition, the viscoelasticity of the polymer melt is improved by TIB‐3CPBA‐TAPA with a mechanical toughening effect.

Factors Influence on Electrophysical Parameters of the Composite Varistors

Purpose. Evaluation influence structural state polymer phase on the response voltage and coefficient nonlinearity of a multilayer varistor based on zinc oxide. Methodology. Zinc oxide consisted of 97% zinc oxide and 3% total oxides of Bi2O3, Co3O4, MnO2, B2O3, SbO3, ZrO2, Al2O3. At a temperature of 1573°K, the synthesis of semiconductor ceramics based on Zinc oxide was carried out. For composite of thermoplastic polymers and Zinc oxide, non-polar and polar polymers, high pressure polyethylene and polyvinylidene fluoride were used. The composites were obtained by hot pressing at the melting temperature of the polymer phase and a pressure of 15 MPa. After that, using silver paste, measuring electrodes 10 mm in diameter were applied to the surface of the synthesized samples, and then current–voltage characteristics were measured. Modification of composites under action of gas-discharge plasma was carried out in a special cell that creates a dielectric-gas-composite system. The structure of the composites was studied by X-ray diffraction analysis and IR spectroscopy. Findings. The obtained experimental results show that the size of the particles of the inorganic phase significantly affects the current-voltage characteristics of the composite varistor: at a given thickness of the composite varistor, the operation voltage decreases markedly, and the nonlinearity coefficient increases. Numerous experimental results obtained by us show that the impact of electric discharge plasma on the polymer Zinc oxide-composite leads to a significant change in the permittivity and the concentration of local levels at the interface of the composite. The results research showed that effect electrical plasma on the opening voltage depends on the polarity of polymer matrices. Moreover, plasma processing itself significantly changes the structure of the polymer phase at composite. Originality. The magnitude of the potential barrier at phase boundary is mainly determined by the volume fraction and size of the main structural element of ZnO ceramics. Changing the structural state of the polymer matrix allows the adjust response voltage and coefficient nonlinearity of volt-ampere characteristic of the multilayer varistor. Practical value. The discovered development of electron-ion processes at polymer phase of the varistor indicates the need to take into account change in its service characteristics from the duration and intensity of use. The result obtained has a certain practical significance, since it indicates not only the reason for the change in properties, but also the need to develop measures to increase the service life of the varistor.

Dissolution dynamics of partially protected poly(4-hydroxystyrene) in tetraalkylammonium hydroxide aqueous solution

A 0.26 M tetramethylammonium hydroxide (TMAH) aqueous solution has been used as a standard developer for manufacturing semiconductor devices. Alternative developers have recently attracted much attention because the 0.26 M TMAH developer may be approaching its performance limit. In this study, we measured the dissolution and swelling behavior of resist polymers in tetraalkylammonium hydroxide (TAAH) aqueous solutions using a quartz crystal microbalance method to clarify the effects of the alkyl chain length of TAAH. The resist polymer was poly(4-hydroxystyrene), whose hydroxyl groups were partially protected with t-butoxycarbonyl groups. When the alkyl chain length of TAAH was increased from two (ethyl) to three (propyl), the dissolution mode markedly changed. The dissolution mode did not depend on the polymer polarity. The change in the dissolution mode is probably caused by the size effect of TAAH, considering the independence of polymer polarity and the discrete change in the dissolution mode.

Effects of Polarity of Polymers on Conformation and Lubricating Film Formation of Adsorbed Films

The conformations and lubricating film formation ability of adsorbed films on metal surfaces formed by poly(alkyl methacrylate) (PAMA) homopolymers with different polarities from nonpolar lubricant oil were investigated. It was found that as the polarity of the polymers became higher, the chains in the adsorbed films adsorbed more loosely to the surfaces (i.e., they formed more loops and tails). The loosely adsorbed chains temporarily trapped free polymer chains flowing into the gap between sliding surfaces, resulting in a much thicker lubricating film. Thus, the sliding surfaces were better protected from wear caused by direct contact. On the other hand, flattened chains occupying in the adsorbed film formed by low polarity-polymers could not trap free polymer chains, resulting in a thinner lubricating film.

Hybrid Interfacial Engineering: An Enabling Strategy for Highly Sensitive and Stable Perovskite Quantum Dots/Organic Heterojunction Phototransistors

All-inorganic lead halide perovskite quantum dots (PQD) have attracted tremendous research interest in the field of phototransistors due to their excellent optoelectronic properties. However, the inefficient charge transport/extraction and high trap-state density of the assembled PQD films seriously limit the photoresponsivity of PQD-based phototransistors. Herein, we demonstrate that these limits can be overcome by adopting a novel device architecture composed of a polar-polymer capping layer on a PQD/organic semiconductor (OSC) heterojunction. The polar polymer film plays the role of both electron trapping and encapsulation, whereas OSC provides the fast transport tracks for charges and PQD serves as the photoactive materials. Owing to the balanced dynamic processes of photogenerated charges, highly sensitive photodetection is achieved, as demonstrated by the peak photosensitivity of 1.5 × 104, a photoresponsivity of 2.1 × 104 A/W, a detectivity of 1 × 1015 Jones, and a high gain of 6.4 × 104 under weak incident light of 3 μW/cm2. Additionally, the phototransistors exhibit superior stability and reproducibility with negligible changes in the output current both in darkness and under illumination after storing for 4 months. The results demonstrate the promising potentials of the polar polymer/PQD/OSC heterojunction for high-performance photodetectors, and the mechanism and strategy described here can be applied to other kinds of quantum dots-based optoelectronic devices.

An Ultrathin Nonporous Polymer Separator Regulates Na Transfer Toward Dendrite-Free Sodium Storage Batteries.

Sodium storage batteries are one of the ever-increasing next-generation large-scale energy storage systems owing to the abundant resources and low cost. However, their viability is severely hampered by dendrite-related hazards on anodes. Herein, a novel ultrathin (8 µm) exterior-nonporous separator composed of honeycomb-structured fibers is prepared for homogeneous Na deposition and suppressed dendrite penetration. The unhindered ion transmission greatly benefitsfrom honeycomb-structured fibers with huge electrolyte uptake (376.7%) and the polymer's inherent transport ability. Additionally, polar polymer chains consisting of polyethersulfone and polyvinylidene customize the highly aggregated solvation structure of electrolytes via substantial solvent immobilization, facilitating ion-conductivity-enhanced inorganic-rich solid-electrolyte interphase with remarkable interface endurance. With the reliable mechanical strength of theseparator, the assembled sodium-ion full cell delivers significantly improved energy density and high safety,enabling stable operation under cutting and rolling. The as-prepared separator can further be generalized to lithium-based batteries for which apparent dendrite inhibition and cyclability are accessible and demonstrates its potential for practical application.

Boosted Mechanical Properties of Polyamide 11 Tube Originated from the Hierarchical Architecture Manipulation by Helical Flow Field

Polyamide 11 (PA11) is a biobased polymer originated from the renewable plant-based resources and thus holds promising potential in reducing the consumption of limited fossil resources and protecting the environment. Compared to the commonly investigated polyolefin, the flow manipulation strategy for improving the mechanical properties of PA11 still remained a huge challenge because the strong intermolecular interactions elevated the difficulty of stretching the polar polymer chains. Herein, a helical flow was introduced in the PA11 tube extrusion by superposing a hoop flow from mandrel rotation onto an axial flow. Then, the helical flow-induced hierarchical architecture was investigated to reveal the effect of intermolecular interactions on the orientation and crystalline structure. Limited by strong hydrogen bonds between the amide groups, the PA11 chains were not stretched sufficiently to form anisotropic shish-kebab crystals but assembled into a helically aligned configuration in amorphous regions, similar to that in natural materials, endowing the as-prepared tube with enhanced hoop kink resistance and axial compression properties which were favorable to the practical application of the thin-wall tube. This study not only can provide a feasible way to tailor the mechanical properties of the PA11 tube by constructing a special multidimensional flow but also is beneficial to the fundamental understanding on the flow-induced crystallization mechanism of polar polymers with strong intermolecular interactions.

Stereoselective Polymerization of Aromatic Vinyl Polar Monomers

AbstractPolar vinyl polymers, a class of polymers with polar groups as side chains, have significant advantages over conventional nonpolar polyolefin materials in terms of viscosity, toughness, interfacial properties (dyeability and printability), and compatibility with solvents or other polymers. Among them, aromatic polar vinyl polymers are of interest because of their good heat resistance properties. In addition, stereoselective polymerization of aromatic polar vinyl monomers has been rapidly developed because the steric structure of the polymer has a significant impact on its physical properties. In this paper, we review the research progress of stereoselective polymerization catalysts for aromatic polar vinyl monomers in recent years, discuss in detail the influence of ligand structure, electronic effect of substituents, spatial site resistance effect, central rare earth metal species and polymerization solvents on the activity and stereoselectivity of polymerization reactions, and explore the possible mechanism of polymerization reaction.