Thermal Crosslinking Research Articles

Poly (vinyl alcohol)/Polyquaternium-7 Anion Exchange Membranes for Alkaline Polymer Electrolyte Fuel Cells

Anion exchange membrane (AEM) is one of the critical components in Alkaline polymer electrolyte fuel cells. This is due to the crucial function in facilitating the process of hydroxide ion conduction. A series of anion exchange membranes (AEMs) were synthesized using poly (vinyl alcohol) (PVA) as the backbone polymer and polyquaternium-7 as the copolymer that provides a hydroxide conducting group source. Thermal and chemical crosslinking was introduced to reduce the excessive swelling of the membranes. The effect of the PVA/PQ7 mass ratio on AEMs performance was investigated. The FTIR study reveals that the spectra exhibit the primary functional groups of PVA, polyquaternium-7, and chemical crosslinking. According to the SEM image, the PVA/PQ7 membranes have smooth and uniform morphology. Water uptake and swelling degree increased with increasing mass ratio of polyquaternium-7 to PVA. AEMs with a polyquaternium-7 to PVA ratio of 0.5 provide the highest IEC and hydroxide conductivity values of 1.52 mmol/g and 9.26 mS/cm at room temperature, respectively.

Tissue-specific gelatin bioink as a rheology modifier for high printability and adjustable tissue properties.

Decellularized extracellular matrix (dECM) has emerged as an exceptional biomaterial that effectively recapitulates the native tissue microenvironment for enhanced regenerative potential. Although various dECM bioinks derived from different tissues have shown promising results, challenges persist in achieving high-resolution printing of flexible tissue constructs because of the inherent limitations of dECM's weak mechanical properties and poor printability. Attempts to enhance mechanical rigidity through chemical modifications, photoinitiators, and nanomaterial reinforcement have often compromised the bioactivity of dECM and mismatched the desired mechanical properties of target tissues. In response, this study proposes a novel method involving a tissue-specific rheological modifier, gelatinized dECM. This modifier autonomously enhances bioink modulus pre-printing, ensuring immediate and precise shape formation upon extrusion. The hybrid bioink with GeldECM undergoes a triple crosslinking system-physical entanglement for pre-printing, visible light photocrosslinking during printing for increased efficiency, and thermal crosslinking post-printing during tissue culture. A meticulous gelatinization process preserves the dECM protein components, and optimal hybrid ratios modify the mechanical properties, tailoring them to specific tissues. The application of this sequential multiple crosslinking designs successfully yielded soft yet resilient tissue constructs capable of withstanding vigorous agitation with high shape fidelity. This innovative method, founded on mechanical modulation by GeldECM, holds promise for the fabrication of flexible tissues with high resilience.

Theoretical, structural, and thermal aspects of nitro-HTPB as a prospective energetic binder–A detailed computational and experimental analysis

This study is focused on several key parameters of nitro-HTPB, such as the theoretical prediction of propulsive performance in composite propellants, determination of microstructural changes on the HTPB backbone before and after nitration, detailed analysis of the thermal decomposition mechanism, and kinetic analysis, to understand its potential as an energetic binder. When compared to conventional AP/Al/HTPB/DOA composition, nitro-HTPB-based propellant with AP/Al/NHTPB/TEGDN composition increases density-specific impulse by 40–50 s, depending on the extent to which the HTPB backbone is nitrated. As evidenced by 2D NMR methods such as 1H–13C HSQC and 1H–1H COSY, nitration only happened on alkene segments via dehydro-nitration, keeping the alkene segment in the process and barely changing the HTPB backbone's olefinic proton percentage (38%). The thermal cross-linking process during the first stage of decomposition of NHTPB begins at about 190 ºC and finishes at about 280 ºC, which is about 130 °C lower than that of HTPB, according to an FTIR analysis of TGA residues. Although nitro-HTPB has a shorter shelf life than HTPB, the kinetic analysis showed that it can be stored for extended periods in tightly packed conditions without degrading its performance, primarily because of its low K (reaction factor) value of 109 min−1. These encouraging results open up new avenues for nitro-HTPB's possible applications as an energetic binder and may eventually encourage other propellant researchers to use it in real-world applications. © 2017 Elsevier Inc. All rights reserved.

Crosslinked Polymer Coatings of Poly (Acrylic Acid-co-acrylamide)/Polyethyleneimine (P(AA-co-AAm)/PEI) on Titanium Alloy with Excellent Lubrication Performance for Artificial Joints

The development of coatings with efficient lubrication and load-bearing capacity is an urgent need for artificial joints. Here, we successfully fabricated poly (acrylic acid-co-acrylamide)/polyethyleneimine (P(AA-co-AAm)/PEI) coating on titanium alloy (Ti6Al4V) surface via UV irradiation and thermal treatment technique. The dual crosslinked network structures were composed of a P(AA-co-AAm) network via free radical polymerization and a PAA-co-PEI network via thermal crosslinking of amine and carboxyl groups. The thermally crosslinked P(AA-co-AAm)/PEI coatings exhibit a stable low friction coefficient (approximately 0.022) and exceptionally low wear volume, with a 93.8% and 92.6% reduction, respectively, in comparison to the pristine Ti6Al4V. These thermally crosslinked P(AA-co-AAm)/PEI hydrogel coatings exhibit excellent lubrication and anti-wear properties, providing a strategy for developing novel lubricating coatings in the biomedical field.

In Situ Thermal Cross-Linking of 9,9'-Spirobifluorene-Based Hole-Transporting Layer for Perovskite Solar Cells.

A novel 9,9'-spirobifluorene derivative bearing thermally cross-linkable vinyl groups (V1382) was developed as a hole-transporting material for perovskite solar cells (PSCs). After thermal cross-linking, a smooth and solvent-resistant three-dimensional (3D) polymeric network is formed such that orthogonal solvents are no longer needed to process subsequent layers. Copolymerizing V1382 with 4,4'-thiobisbenzenethiol (dithiol) lowers the cross-linking temperature to 103 °C via the facile thiol-ene "click" reaction. The effectiveness of the cross-linked V1382/dithiol was demonstrated both as a hole-transporting material in p-i-n and as an interlayer between the perovskite and the hole-transporting layer in n-i-p PSC devices. Both devices exhibit better power conversion efficiencies and operational stability than devices using conventional PTAA or Spiro-OMeTAD hole-transporting materials.

Environmentally friendly separators based on cellulose diacetate-based crosslinked networks for lithium-ion batteries

Biomass fibers are recognized as degradable and renewable green natural polymer materials. However, research on biomass fiber-based lithium battery separators is still relatively limited. Here, a kind of cellulose diacetate-based composite separator for lithium batteries was investigated via electrostatic spinning technology. In this study, M-CDA/PEO/BM composite separators were obtained by modifying fiber-based nonwovens through deacetylation, followed by an infiltration process and thermal cross-linking reaction to introduce boehmite (BM) and polyethylene oxide (PEO). Wherein the infiltrating solution is composed of polyethylene glycol diglycidyl ether (PEGDE), polyetheramine (DPPG), and boehmite particles. The results demonstrate that this nanofibre composite separator exhibits good heat tolerance (no shrinkage at 200 °C), excellent wettability (contact angles only 15.1°), and high ionic conductivity (2.83 mS cm−1) in electrolytes. Additionally, the cells utilizing the composite separator exhibited superior cycle performance and better multiplier performance (170 mAh·g−1 at 0.5C) compared to the polypropylene separator that is currently available in the market, under identical circumstances. This renewable composite possesses remarkable properties that position it as a highly promising option for lithium-ion battery separators with exceptional performance.

Stretchable and ultra‐light non‐woven thermal material with effective photo‐thermal conversion based on solution blow spinning technology

AbstractAn ideal insulation material has long been envisioned as one that not only minimizes heat loss but also provides additional heat. This study presents a non‐woven fabric, comprising ultra‐fine fibers embedded with zirconium carbide nanoparticles (ZrC NPs), prepared via solution blow spinning (SBS) and thermal crosslinking technology. Our results suggest that the fluffily‐structured elastomer, fabricated using rigid polystyrene and flexible polyurethane, exhibits high porosity (96.96%), ultra‐light characteristics (volume density of 47.12 mg cm−3), and effective heat retention (thermal conductivity of 23.1 mW mK−1 at −40°C). Moreover, the fabric demonstrates remarkable fracture strength (206.38 kPa), high elongation at break (34.5%), and superior elasticity even after 100 compression cycles at 40% strain. Despite the fact that introducing 12% ZrC increases the thermal conductivity of the base fabric by 6%, the NPs endow the material with an excellent photothermal conversion function. Following 10 min of exposure to visible light, the surface temperature increases to 71.5°C. Given its impressive performance, this novel non‐woven fabric demonstrates significant potential for applications in the field of cold protection.

Plasticization resistant gas separation membranes derived from polyimides exhibiting polyethylene-oxide moieties

Despite exhibiting excellent thermal/chemical stability, mechanical robustness, and easy processability, which makes them attractive candidates for gas separation applications, aromatic polyimides are susceptible to plasticization. This study proposes an effective approach to suppress CO2-induced plasticization in a high fractional free volume (FFV) polyimide (PI*) derived from 4,4’-(hexafluoroisopropylidene)diphthalic anhydride and 2,4,6-trimethylphenyldiamine. PI* was first modified by incorporating 3,5-diaminobenzoic acid (DABA) and polyethylene oxide segments (PEO) into the polymer backbone, with the goal of partially removing PEO through high temperature (450 °C) pyrolysis, thereby increasing the membrane FFV and, simultaneously, providing enhanced plasticization resistance via DABA cross-linking. To mitigate the effects of themomechanical history, the membranes were aged prior to the thermal treatment process. However, the great enhancement in plasticization resistance was not accompanied by a parallel improvement in the separation performance relative to PI*. To address this shortcoming, a microporous organic polymer (POP) was blended with the polyimides to fabricate mechanically-robust mixed matrix membranes (MMMs). Remarkably, MMM plasticization was suppressed even without the aid of thermal crosslinking for PEO-containing PI*, which was rationalized by molecular simulation invoking the formation of hydrogen bonds between the lactam groups of the POP and PEO moieties.

Chitosan-based intelligent polymeric networks for site-specific colon medication delivery: A comprehensive study on controlled release of diloxanide furoate and network formation dynamics

Oral medications are prone to gastric degradation and enzymatic inactivation, diminishing their efficacy. This study investigates a solution by developing intelligent polymeric networks, incorporating chitosan, methacrylic acid, N, N, methylene bisacrylamide, and montmorillonite clay, to enable the controlled release of Diloxanide Furoate (DF), an anti-protozoal drug. Employing a swelling-assisted diffusion technique, drug loading percentages varied from 63.96 % to 76.82 % among different formulations. Increased chitosan and methacrylic acid content enhanced drug loading, while N, N, methylene bisacrylamide and montmorillonite clay demonstrated an inverse relationship affecting diffusion and swelling.Equilibrium swelling studies unveiled formulation-dependent behaviors, with chitosan reducing swelling and methacrylic acid promoting it. Higher N, N, methylene bisacrylamide concentrations decreased swelling, indicating a denser cross-linked structure, while montmorillonite clay reduced hydrophilicity and swelling capacity. Further analyses confirmed successful gel formation, particularly in formulations with higher chitosan, methacrylic acid, and N, N, methylene bisacrylamide content, while montmorillonite clay limited gel fraction due to restricted polymer chain mobility. Techniques such as Fourier transform infrared spectroscopy, Differential scanning calorimetry, and thermal gravimetric analyses supported network development, enhancing thermal stability and cross-linking density. This research underscores the flexibility of polymeric networks for precise drug delivery, offering potential advancements in targeted therapies for various medical conditions.

Preparation and Space Charge Properties of Functionalized Zeolite/Crosslinked Polyethylene Composites with High Thermal Conductivity.

Nanocomposite doping is an effective method to improve the dielectric properties of polyethylene. Meanwhile, the introduction of thermal conductivity groups in crosslinked polyethylene (XLPE) is also an effective way to improve the thermal conductivity. Nano-zeolite is an inorganic material with a porous structure that can be doped into polyethylene to improve the insulation performance. In this paper, hyperbranched polyarylamide (HBP) with a high thermal conductivity and an auxiliary crosslinking agent (TAIC) was grafted on the surface of ZSM-5 nano-zeolite successively to obtain functionalized nano-zeolite (TAICS-ZSM-5-HBP) (the "S" in TAICS means plural). The prepared functionalized nano-zeolite was doped in polyethylene and grafted under a thermal crosslinking reaction to prepare nanocomposites (XLPE/TAICS-ZSM-5-HBP). The structural characterization showed that the nanocomposite was successfully prepared and that the nanoparticles were uniformly dispersed in the polyethylene matrix. The space charge of the TAICS-ZSM-5-HBP 5wt% nanocomposite under a high electric field was obviously inhibited. The space charge short-circuit test showed that the porous structure of the nano-zeolite introduced more deep traps, which made the trapped charge difficult to break off, hindering the charge injection. The introduction of TAICS-ZSM-5-HBP particles can greatly improve the thermal conductivity of nanocomposites. The thermal conductivity of the XLPE/5wt% and XLPE/7wt% TAICS-ZSM-5-HBP nanocomposites increased by 42.21% and 69.59% compared to that of XLPE at 20 °C, and by 34.27% and 62.83% at 80 °C.

Inhibiting Ion Migration Through Chemical Polymerization and Chemical Chelation Toward Stable Perovskite Solar Cells.

The migration of ions is known to be associated with various detrimental phenomena, including current density-voltage hysteresis, phase segregation, etc., which significantly limit the stability and performance of perovskite solar cells, impeding their progress toward commercial applications. To address these challenges, we propose incorporating a polymerizable organic small molecule monomer, N-carbamoyl-2-propan-2-ylpent-4-enamide (Apronal), into the perovskite film to form a crosslinked polymer (P-Apronal) through thermal crosslinking. The carbonyl and amino groups in Apronal effectively interact with shallow defects, such as uncoordinated Pb2+ and iodide vacancies, leading to the formation of high-quality films with enhanced crystallinity and reduced lattice strain. Furthermore, the introduction of P-Apronal improves energy level alignment, and facilitates charge carrier extraction and transport, resulting in a champion efficiency of 25.09 %. Importantly, P-Apronal can effectively suppress the migration of I- ions and improve the long-term stability of the devices. The present strategy sets forth a path to attain long-term stability and enhanced efficiency in perovskite solar cells.

Inhibiting Ion Migration Through Chemical Polymerization and Chemical Chelation Toward Stable Perovskite Solar Cells

AbstractThe migration of ions is known to be associated with various detrimental phenomena, including current density‐voltage hysteresis, phase segregation, etc., which significantly limit the stability and performance of perovskite solar cells, impeding their progress toward commercial applications. To address these challenges, we propose incorporating a polymerizable organic small molecule monomer, N‐carbamoyl‐2‐propan‐2‐ylpent‐4‐enamide (Apronal), into the perovskite film to form a crosslinked polymer (P‐Apronal) through thermal crosslinking. The carbonyl and amino groups in Apronal effectively interact with shallow defects, such as uncoordinated Pb2+ and iodide vacancies, leading to the formation of high‐quality films with enhanced crystallinity and reduced lattice strain. Furthermore, the introduction of P‐Apronal improves energy level alignment, and facilitates charge carrier extraction and transport, resulting in a champion efficiency of 25.09 %. Importantly, P‐Apronal can effectively suppress the migration of I− ions and improve the long‐term stability of the devices. The present strategy sets forth a path to attain long‐term stability and enhanced efficiency in perovskite solar cells.

Ultra-thin and high-voltage-stable Bi-phasic solid polymer electrolytes for high-energy-density Li metal batteries

Solid-state electrolytes (SSEs) are essential materials in all-solid-state lithium-metal batteries. However, a comprehensive SSE possessing high ionic conductivity, broad electrochemical window, and high thermal stability remains elusive. In this work, a novel bi-phase SSE featuring a shape memory effect is developed by in-situ thermal cross-linking of 2-ethyl cyanoacrylate (CA), polyethylene glycol methyl ether acrylate (PEGMEA), succinonitrile (SN), and fluoroethylene carbonate (FEC) additives. Due to the phase separation phenomenon and interfacial Li-ion conduction, the bi-phase SSE exhibits a room-temperature ionic conductivity of 1.9 mS cm−1. Meanwhile, the bi-phase SSE exhibits a high oxidation potential of 4.9 V (vs Li/Li+), and a lithium-ion transference number (tLi+) of 0.56. Coupling with LiNi0.8Co0.1Mn0.1O2 (NCM 811) cathode and 11 µm bi-phase SSE, solid-state lithium metal batteries (SSLMBs) demonstrate long-term cycling stability (capacity retention > 92% after 250 cycles), excellent rate performance (126 mA h g−1 at 2 C, and high-voltage stability (208 mA h g−1 at 4.5 V). This investigation demonstrates the potential of bi-phase SSEs as a promising material for the development of high-performance SSLMBs.

Formulation strategies for the development of high drug-loaded amorphous solid dispersions

Amorphous solid dispersions (ASD) have gained tremendous attention over the past two decades as one of the most promising techniques for enhancing the solubility of poorly water-soluble drugs. However, low drug loading is one of the major challenges of ASD technology that limits its commercialization to only a few drug candidates. Increasing the drug loading increases the risk of recrystallization during storage (solid state) and/or during dissolution (solution state). Various formulation and process-related strategies have been explored that open the possibility of formulating high drug-loaded ASDs without the risk of recrystallization. Here, we review various formulation approaches, such as the use of surfactants, mesoporous silicas, polymer combinations, in situ thermal crosslinking, structural modification of polymeric carriers, and surface nanocoating using minerals. We also discuss the mechanisms by which these approaches inhibit solid state and/or solution state recrystallization.

Fabrication of Porous Heteroatom‐Doped Carbon Networks via Polymer‐Assisted Rapid Thermal Annealing

AbstractPorous carbon materials have increasingly drawn interest for applications ranging from supercapacitive energy storage to bioengineering. However, a simple and scalable fabrication process of such materials, employing low‐cost chemical compounds without sacrificing morphological and chemical control, remains lacking. Here, a novel, rapid, continuous bottom‐up strategy for synthesizing structurally tunable porous carbon network films on insulating and conductive substrates is reported. By employing rapid thermal annealing (RTA) of a commercial polyacrylonitrile‐based blend, simultaneous phase separation and thermal crosslinking are induced, effectively freezing the structure. Subsequent burning of degradable components generates a porous carbon framework ( ≈ 360 to 700 nm) doped with nitrogen and oxygen atoms. Introducing a boron‐containing reagent in the precursor solution enables boron doping and pore size reduction as small as 20 nm, enhancing materials' performance. The direct fabrication of micro‐supercapacitors on stainless steel substrates is demonstrated, achieving an areal capacitance of 12.7 mF cm−2 at 50 mV s−1, with ≈98% retention after 10 000 charge/discharge cycles. The benefit of boron doping is further highlighted for wound healing applications. Because RTA is already an established industrial method, this platform directly facilitates the synthesis of functional porous heteroatom‐doped carbon structures using commercial polymers and dopants for various applications.

Robust and stretchable Ti3C2Tx MXene/PEI conductive composite dual-network hydrogels for ultrasensitive strain sensing

The development of high-performance hydrogels with superior strength, stretchability, and conductivity is critical to the practical application of flexible sensors. In this study, we employed a strategy that involves introducing physical cross-linking points, creating a double network, and adding nanofillers. By utilizing a two-step method that involves thermal cross-linking and post-immersion cross-linking, and using two common metal ions to crosslink different polymer networks, we successfully developed a conductive composite dual-network hydrogel. In addition, the incorporation of modified MXene has significantly improved the strength and toughness of the hydrogel. The resulting hydrogel exhibits impressive mechanical properties, including a tensile strength of 2.64 MPa and elongation at break of 689%, as well as high toughness of 10.25 MJ·m−3 and conductivity of 1.89 S/m. When applied as a flexible sensor in electronic skin, the sensor demonstrates a wide operating range (>300%), high sensitivity (GF = 4.64), and excellent linear detection ability (R2 = 0.99).

In-situ crosslinked polyetherimide/BNNS composites with ultrahigh charged-discharged efficiency at high temperature

High performance dielectric polymer composites for capacitive energy storage have been a hot topic in recent years. However, dielectric materials tend to breakdown at high temperature, and its charged-discharged efficiency is greatly reduced. Therefore, preparing high-efficient high-temperature dielectric material is the main challenge in this field. In this work, based on the synergistic effect of in-situ composite and controlled thermal cross-linking, the thermal conducting nano filler and crosslinking system composite has ultra-high charged-discharged efficiency at high temperature. It is proved that the addition amount of BNNS for the peak performance of this kind of composite is 10 vol% and the discharge energy density is 4.58 J/cm3 and the charged-discharged efficiency reaches 96 % at 150 °C and 500 MV/m. At 200 °C and 300 MV/m, these are 1.76 J/cm3 and astonishing 95 %. It is expected to be a candidate for a new generation of high temperature resistant dielectric materials.

Enhanced plasticization resistance of hollow fiber membranes for helium recovery from natural gas based on a novel thermally crosslinkable polyimide

Herein, we develop and investigate the performance of defect-free hollow fiber membranes (HFMs) based on a novel 6FDA-mPDA0.65-DABA0.3-TFMB0.05 copolyimide for helium separation from multi-component natural gas. The copolyimide is synthesized using a two-step condensation polymerization, and the hollow fiber membranes are fabricated using a dry-jet/wet-quench spinning approach. Thermal crosslinking of hollow fiber membranes is conducted to enhance plasticization resistance. The crosslinked membranes exhibit improved He selectivity (α(He/CH4) = 259) compared to the pristine hollow fiber membrane (α(He/CH4) = 210). Gas permeation tests are performed on the pristine and crosslinked hollow fiber membranes using pure-gas and mixed-gas at various pressures. The results demonstrate that the crosslinked membranes effectively resist plasticization even under high-pressure gas feeds containing CO2, light hydrocarbons, and heavy hydrocarbons. In contrast, the uncrosslinked membranes experience plasticization, dramatically decreasing selectivity. The findings provide valuable insights into the plasticization behavior of different impurity compounds in hollow fiber membranes and highlight the potential of thermal crosslinking as an effective strategy to improve the plasticization resistance of HFMs for He recovery. These defect-free and plasticization-resistant membranes hold promise for efficient He recovery from mixed-gas streams, offering a viable and energy-efficient alternative to traditional separation methods.

Identification and characterisation of taste-enhancing peptides from oysters (Crassostrea gigas) via the Maillard reaction.

Oysters, which are flavourful edible marine products, have been utilised to produce Maillard reaction products (MRPs), which contribute to saltiness enhancement. Here, the molecular weight distribution, free amino acids, and taste characteristics of MRPs were analysed, while ultraviolet light was used to observe the Maillard reaction. Both thermal degradation and cross-linking reactions occur during the Maillard reaction. When the Maillard reaction time was 90min, the saltiness, umami, and richness of the MRPs peaked, however bitterness reached its lowest value. Moreover, at an MRP concentration of 1.5mg/mL, salts were reduced by 35.71% in a 3mg/mL sodium chloride solution without reducing saltiness, based on sensory evaluation. Glycation sites of the MRPs, which are crucial for saltiness enhancement and derived from a variety of protein sources, were determined using nano-HPLC-MS/MS analysis. Our study establishes the foundation for preparing salt-enhancing peptides, accelerating the popularisation of oyster-derived flavouring agents.

Wide Bandgap Heterostructured Dielectric Polymers by Rapid Photo‐Crosslinking for High‐Temperature Capacitive Energy Storage

AbstractPolymer dielectrics capable of operating stably at high temperatures (>150 °C) are urgently in great demand to catch up with the booming electric power systems. Enhancing the heat resistance of polymers is typically achieved through thermal crosslinking with the use of crosslinking agents. Unfortunately, the conventional thermal crosslinking faces challenges in terms of commercialization due to its complex fabrication, inevitable introduction of small molecule impurities, and significant time and energy consumption. Here, a convenient, impurity‐free, time and energy efficient photo‐crosslinking method to create wide bandgap heterostructures within a dielectric polymer matrix, is presented. Remarkably, this approach achieves synergistically enhanced heat resistance and electrical insulation. Surprisingly, the crosslinked polymer exhibits an unprecedented Weibull characteristic breakdown strength of 1057 and 810 MV m−1 at room temperature and at 150 °C, respectively, which corresponds to superior energy storage densities of 14.28 and 5.55 J cm−3 with a charge–discharge efficiency of 90%, respectively. Furthermore, the polymer demonstrates an excellent electrical breakdown self‐healing character. These remarkable achievements, combined with the convenient and cost‐effective fabrication process, highlight the potential of cinnamate photo‐crosslinking in advancing high‐performance polymer dielectrics.