Crosslinking Temperature Research Articles

Investigating the impact of manufacturing conditions on crack growth rate in nitrile butadiene rubber for enhanced service life – Part 02: Crosslink density via multi-stage swelling analysis

The importance of the state of cure of elastomer components with regard to fatigue behavior and thus also durability was already discussed in more detail in Part 01 of the paper. It was shown that crosslinking time and temperature have an enormous influence on the crack growth behavior in nitrile butadiene rubber (NBR). In the course of this, a fourfold deceleration in crack growth was observed with a 20 K increase in manufacturing temperature. To confirm this trend, test specimens were produced at 180 °C. Crack growth was found to be 40 times slower, especially in high tearing energy ranges, compared to 150 °C. To analyze the observed behavior in more detail, cylindrical samples were taken from the plain strain test specimens (used for the crack growth measurements), and multi-stage swelling was performed with them. This allowed a detailed analysis of the degree of cure and the sulfur chain composition. It was found that the crosslink density decreases with increasing manufacturing temperature due to decomposition and the proportion of polysulfidic crosslinks decreases with increasing heating time due to desulfurization. Furthermore, a correlation between the results found by means of the rubber process analyzer (RPA) and the swelling results could be established looking at the maximum transmitted torque during the isothermal crosslinking phase.

Preparation of photo-crosslinked microalgae-carboxymethyl chitosan composite hydrogels for enhanced wound healing

Integrating microalgae into wound dressings has proven effective in promoting chronic wound healing through photosynthesis-induced oxygen release. However, challenges such as high crosslinking temperatures and prolonged gel molding processes limit microalgae growth and reduce the overall therapeutic impact. In this work, inspired by cell-symbiotic photo-crosslinked hydrogels, we present a novel photo-crosslinked microalgae carboxymethyl chitosan composite hydrogel. This hydrogel completes crosslinking at room temperature within 30 s, enhancing chronic wound healing. The composite gel incorporates photosynthesizing unicellular microalgae (Chlamydomonas reinhardtii) and the antimicrobial agent ciprofloxacin during preparation. In light, the gel continues to photosynthesize, releasing oxygen while simultaneously acting as an antibacterial agent. This dual action results in the upregulation of CD31 and VEGFA levels and the downregulation of HIF-1α levels in diabetic wounds. The wound closure rate reached approximately 96.70 % on day 12 in the composite gel group, compared to only 78.98 % in the control group. Therefore, the composite gel promotes healing by reducing local hypoxia, encouraging angiogenesis, and lowering infection risk. These results suggest that photo-crosslinked microalgae composite gels provide an effective strategy for localized oxygen delivery to promote wound healing and offer a viable method for rapidly preparing living biomaterials under suitable conditions.

Exosome Loaded Protein Hydrogel for Enhanced Gelation Kinetics and Wound Healing.

Exosomes are being increasingly explored in biomedical research for wound healing applications. Exosomes can improve blood circulation and endocrine signaling, resulting in enhanced cell regeneration. However, exosome treatments suffer from low retention and bioavailability of exosomes at the wound site. Hydrogels are a popular tool for drug delivery due to their ability to encapsulate drugs in their network and allow for targeted release. Recently, hydrogels have proven to be an effective method to provide increased rates of wound healing when combined with exosomes that can be applied noninvasively. We have designed a series of single-domain protein-based hydrogels capable of physical cross-linking and upper critical solution temperature (UCST) behavior. Hydrogel variant Q5, previously designed with improved UCST behavior and a significantly enhanced gelation rate, is selected as a candidate for encapsulation release of exosomes dubbed Q5Exo. Q5Exo exhibits low critical gelation times and significant decreases in wound healing times in a diabetic mouse wound model showing promise as an exosome-based drug delivery tool and for future hybrid, noninvasive protein-exosome design.

Modified guanidine gel fracturing fluid system and performance optimization for ultra-deep and ultra-high temperature oil and gas reservoirs

The development of deep high-temperature oil and gas reservoirs gives rise to a rise in reservoir temperature along with the depth of the oil reservoir, thereby imposing higher requirements on the heat resistance of fracturing fluid. Guar gum fracturing fluid has difficulty tolerating temperatures exceeding 160 °C, thereby demanding the development of corresponding cross-linking agents, temperature stabilizers, and other additives to enhance the thermal stability of the fracturing system. Considering the distinctive characteristics of deep and ultra-deep reservoirs, such as extreme burial depth (exceeding 6000 m), ultra-high temperature (higher than 160 °C), and high fracturing pressure, an experimental modification of a guar gum fracturing fluid system was carried out, specifically tailored for ultra-high temperatures. The experiment identified and selected individual agents for ultra-high temperature fracturing fluids, including crosslinking agents, thermal stabilizers, flowback aids, and clay inhibitors. Through rigorous experimentation, these key agents for an ultra-high temperature fracturing fluid system have been successfully developed, including the optimal thickener GBA1-2, crosslinking agent BA1-1, anti-swelling agent FB-1, and gel breaker TS-1. The evaluation of diverse additive dosages has facilitated the development of an optimal guar fracturing fluid system, which exhibits outstanding high-temperature resistance while minimizing damage and friction. The outcomes of our experiments indicate that even after subjecting our ultra-high temperature fracturing fluid to 2 h of shearing at 170 s−1 at 180 °C, its viscosity remained above 200 mPa s—a distinct proof of its superior performance in withstanding high temperatures. This achievement represents a substantial progress in providing a suitable fracturing fluid system for the transformation and stimulation of ultra-deep and ultra-high temperature reservoirs, and also lays a solid foundation for further exploration and application in related fields in the future.

Effect of ultrasonic pretreatment on physicochemical, thermal, and rheological properties of chemically modified corn starch

This study investigated the effects of ultrasonic and three chemical individual and dual modification treatments on corn starch's physicochemical, thermal, and rheological properties. Ultrasonication and the three chemical treatments disrupted the starch granules with a decrease in particle size and a significant increase in the ζ-potential. The hydrophilicity of ultrasonic-oxidized dual-modified starch (U-O-CS) was the highest, at 0.854 g/g. The lipophilicity of ultrasonic-esterified dual-modified starch (U-E-CS) was the highest, at 1.485 g/g. The gelatinization temperature of ultrasonic, oxidation, and cross-linking modified starches increased significantly, with cross-linking starches being the largest. Oxidative treatment significantly decreased the starch's G' and G" and weakened the textural properties. The rheological properties of U-O-CS were further weakened. The G' of the starch decreased after the esterification treatment, while the G" increased, and the textural properties were cut. The maximum rheological and textural properties were obtained for crosslinked modification, with a hardness value of 284.70 g.

Investigating Cross-Linking Parameters and Molecular Arrangement in Liquid Crystalline Epoxy Monomer with Aromatic Diamine: DSC-TOPEM® and WAXS Analysis.

This study presents the characterization of cross-linking parameters of a liquid crystalline epoxy monomer with an aromatic diamine as a curing agent. The mixture tested consisted of bis [4-(10,11-epoxyundecanoyloxy)benzoate] p-phenylene (LCEM) and 1,3-phenylenediamine (1,3-PDA). This paper focuses on the structural characterization of such systems using X-ray analysis. To investigate this, a comprehensive analysis was conducted using Differential Scanning Calorimetry (DSC) and Wide-Angle X-ray Scattering (WAXS). Through DSC analysis, the curing behavior and transition temperature of the liquid crystal epoxy system were established. To fully characterize the cross-linking of the system, a novel technique called DSC-TOPEM® was employed. The use of this technique enabled real-time monitoring of the curing process and provided precise information on the cross-linking energy, which resulted in the finding that the mixture was cross-linking faster than expected. WAXS analysis was performed to assess the structural changes formed during the cross-linking. The results of this analysis confirm that lower cross-linking temperatures of the mixture cause better ordering of mesogens than higher ones.

Inter-crosslinked spirocyclic mixed matrix membranes exhibiting enhanced gas permeability, selectivity, and plasticization resistance

Poor interfacial compatibility is the most common issue inhibiting performance enhancement in mixed matrix membranes (MMM) for gas and liquid separations. To address this issue, we fabricated highly selective and permeable inter-crosslinked mixed matrix membranes (IcMMMs) based on carboxylic-acid functionalized polymer of intrinsic microporosity-1 (CPIM) containing up to 30 wt % triptycene-isatin polymer porous network (PPN) particles. Polymer-filler inter-crosslinking is accomplished via thermal decarboxylation at 200 °C, which is the lowest temperature this reaction has been found to occur in the literature. This low temperature circumvents potential issues with degradation of porous supports or gutter layer materials, and thus enables these materials to be integrated into traditional membrane processes. The resulting IcMMMs exhibit gel fractions above 90 %. Beyond IcMMMs, membranes based on neat CPIM, thermally crosslinked CPIM, as well as non-crosslinked CPIM-PPN mixed matrix membranes were fabricated to elucidate the individual and synergistic effects of filler inclusion and thermal treatment. In addition to showing upper bound permeability-selectivity performance, IcMMMs also exhibit an almost unprecedented stability against plasticization upon extended exposure to CO2 up to 50 atm or above. This study shows that crosslinking across the polymer-filler interface is the key feature to achieve simultaneous enhancement in permeability, selectivity, and stability. To elucidate the molecular mechanism of these enhancements in the IcMMMs with respect to the baseline materials, permeability was broken into its sorption and diffusion contributions and an energetic analysis of sorption was performed. The low cost of PPNs coupled with the mild crosslinking temperature make this approach highly scalable, resulting in materials exhibiting high rigidity and structural stability with the potential to excel in aggressive separations, such as organic solvent separations or high-CO2 content, high-pressure natural gas sweetening.

Karakterisasi Komposit Polimer dengan Matriks Polistirena dan Bahan Pengisi dari Berbagai Limbah Pabrik Kelapa Sawit

The first stage of this research was to make polystyrene grafted with maleic anhydride for making the couping agent with other filling compound. In the second stage, the polystyrene matrix grafted with maleic anhydride was combined with filler material derived from palm oil mill waste using the dry mixing method with an internal mixer. Among several variables tested, the optimum composition of the polymer composite was found to be Polystyrene grafted with maleic anhydride: sludge: boiler ash in a ratio of 60:25:15. This composition exhibited a Young's modulus of 856.752 MPa, a tensile strength of 6.057 MPa, and an elongation at break of 0.775%. Differential Scanning Calorimetry (DSC) testing revealed a glass transition temperature of 403.22°C, a crystallization temperature of 426.39°C, and a cross-linking indication temperature of 478.64°C. Scanning Electron Microscopy (SEM) tests showed an even distribution of the material. Fourier-transform infrared (FT-IR) spectroscopy indicated a decrease in absorption peaks at 3024.94 cm⁻¹ and 3025.15 cm⁻¹, while the polystyrene characteristics at the wave number 1600.57 cm⁻¹ appeared sharper. The sound absorption test results met the ISO 11654:1997 standard for the rating level of sound absorption coefficient in materials, achieving Class D and C sound absorption with an αₙₓ value ranging from 0.328 to 0.793.

Formulation and characterization of ionically crosslinked gellan gum hydrogels using trilysine at low temperatures for antibody delivery

Research of the nontraditional polysaccharide gellan gum (GG) is a growing space for the development of novel drug delivery systems due to its tunable physic-mechanical properties, biocompatibility, and stability in a wide range of environments. Unfortunately, high temperature crosslinking is often required, representing a limiting factor for the incorporation of thermosensitive therapeutic agents. Here, we demonstrated that GG can be crosslinked at a low temperature (38 °C) using a simple fabrication process that utilizes trilysine as an alternative to traditional mono- or divalent ion crosslinkers. While elevated temperature mixing is still required to form a clear GG solution, crosslinking of 0.5 – 1 % GG (w/v) in the presence of trilysine (0.03 % - 0.05 % w/v) was achieved at 38 °C resulting in hydrogels with suitable working formulations to facilitate syringe loading. Low injection forces (< 20 N), and biocompatibility was evaluated with normal human dermal fibroblast (cell viability > 90 %). Frequency sweep showed a transition from purely liquid-like behavior to gel-like behavior with increased trilysine concentration. A temperature dependent behavior was lost with higher trilysine concentrations, indicating stable hydrogel formation. NMR results suggest that trilysine participates in gelation via both ionic interactions between the primary amines of trilysine and the carboxylate residues of glucuronic acid and hydrogen bonding. Released studies showed that GG hydrogels can entrap and provide sustained release of IgG in relation to the crosslinker, and antibody concentration used, with a burst release within the first 24 h (∼80 % cumulative released) followed by a sustained released for up to 5 days. Overall, findings demonstrate a promising nontoxic injectable hydrogel that requires lower crosslinking temperatures, is simple to manufacture and serves as a carrier of thermosensitive therapeutic agents.

Synthesis, characterization and film preparation of 6FDA-based polyimides with polar groups arranged for thermal crosslinking

Abstract Thermal crosslinking of polyimides is a relevant methodology to increase their chemical resistance. This reaction is induced by heating after polymerization. Although this reaction is considered a viable route to modify polyimides, there is controversy over the specific temperature for the reaction. To contribute to the knowledge of crosslinked structures, we performed a differential scanning calorimetric (DSC) and solubility test studies on a series of polyimides with different molar ratios of carboxylic acid groups. With 3,5-diaminobenzoic acid (DABA) as a source of carboxylic acid groups, the copolyimides were synthesized from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4ʹ-hexafluoropropylidenebis(p-phenylenoxy)dianiline (6FPA) to form blocks of 6FDA:6FPA (n) and 6FDA:DABA (m) from m = 0–100 %. Flat films were prepared at 50 ± 3 µm with polyimides. In the thermogram of the flat films, a heat absorption zone associated with the decarboxylation reaction was identified with an endothermic minimum at 260 °C, which was assigned to the crosslinking temperature. Furthermore, heating time was varied for 3–36 h to determine the insolubility of the thermally crosslinked polyimide; from 24 h of heating the polyimide were insoluble. The polyimides were thoroughly characterized by ATR-FTIR, 1H NMR, TGA, SEM, the fractional free volume (FFV) was determined by the Bondi’s group contribution method and solubility to different organic solvents. The FFV of crosslinked polyimides increases relative to pristine polyimides by 2 % for those with higher DABA content and 40 % for those with lower DABA content. Finally, also the glass transition temperature increases in the crosslinked polyimides relative to the pristine ones from 280 °C for the lowest DABA content to 402 °C for the highest DABA content, demonstrating the increase in the thermal resistance of the structure.

Novel porous hydrogel beads based on amidoxime modified polymer of intrinsic microporosity for efficient cationic dye removal

Due to the high surface area and facile functionalized or modified groups of polymers of intrinsic microporosity, and the hydrophilicity of sodium alginate (SA), a simple strategy was proposed for preparing porous composite hydrogel beads with excellent cationic dye adsorption capacity and selectivity. The porous composite hydrogel beads were prepared by introducing the amidoxime modified polymers of intrinsic microporosity (AOPIM-1) into SA polymer solution and then dropping the mixture into CaCl2 aqueous solution at low temperature for crosslinking. The prepared porous SA/AOPIM-1 hydrogel beads performed excellent adsorption capacity on Rhodamine B (RhB) from aqueous solution and the Langmuir model was suitable for describing the adsorption behavior of RhB on porous SA/AOPIM-1 hydrogel beads. It is surprising that the maximum theoretical adsorption capacity obtained by fitting the Langmuir model was up to 1648.3 mg·g−1. More importantly, porous SA/AOPIM-1 hydrogel beads showed outstanding selective adsorption capacity for cationic dyes in the mixed anionic and cationic dyes solution. Besides, the adsorption capacity of porous SA/AOPIM-1 hydrogel beads could maintain above 80 % of the initial adsorption capacity after 10 adsorption/desorption cycles. The above results indicate that porous SA/AOPIM-1 hydrogel beads can be used as a promising adsorbent with for effective removal of dyes from wastewater treatment.

Boosting Hole Mobility: Indenofluorene-Arylamine Copolymers and Their Impact on Solution-Processed OLED Performance.

We introduce three newly designed thermally cross-linkable hole transport copolymers (PIF-TPD, PIF-F2PCz, and PIF-TPAPCz) for improving the performance of solution-processed organic light-emitting diodes (s-OLEDs). These copolymers, designed through a strategic molecular approach with benzocyclobutene (BCB) and styrene-based cross-linking monomers, show high solvent resistance at a low cross-linking temperature (150 °C). Furthermore, these conjugated copolymers based on planar indenofluorene with three different hole transport (HT) units, exhibit outstanding charge carrier mobility (1.61 × 10-2 cm2 V-1s-1), demonstrated by comparing hole reorganization energy and electronic coupling strength of HT units. Despite these copolymers showing the overall vertical orientation in the horizontal dipole moment measurement results, we demonstrated that the HT units can exhibit the preferred orientation, contributing to high hole transport properties. As a result, they perform exceptionally well as hole transport layers in green phosphorescent s-OLEDs, achieving a maximum external quantum efficiency of 15.3% and a maximum current efficiency of 53.9 cd A-1 with a small efficiency roll-off despite their relatively low triplet energy levels. These results are comparable to vacuum-deposited OLEDs, highlighting the potential of these copolymers in advancing OLED technology for display panels and lighting applications.

Enhanced fabrication of size-controllable chitosan-genipin nanoparticles using orifice-induced hydrodynamic cavitation: Process optimization and performance evaluation

Chitosan nanoparticles (NPs) possess great potential in biomedical fields. Orifice-induced hydrodynamic cavitation (HC) has been used for the enhancement of fabrication of size-controllable genipin-crosslinked chitosan (chitosan-genipin) NPs based on the emulsion cross-linking (ECLK). Experiments have been performed using various plate geometries, chitosan molecular weight and under different operational parameters such as inlet pressure (1–3.5 bar), outlet pressure (0–1.5 bar) and cross-linking temperature (40–70 °C). Orifice plate geometry was a crucial factor affecting the properties of NPs, and the optimized geometry of orifice plate was with single hole of 3.0 mm diameter. The size of NPs with polydispersity index of 0.359 was 312.6 nm at an optimized inlet pressure of 3.0 bar, and the maximum production yield reached 84.82 %. Chitosan with too high or too low initial molecular weight (e.g., chitosan oligosaccharide) was not applicable for producing ultra-fine and narrow-distributed NPs. There existed a non-linear monotonically-increasing relationship between cavitation number (Cv) and chitosan NP size. Scanning electron microscopy (SEM) test indicated that the prepared NPs were discrete with spherical shape. The study demonstrated the superiority of HC in reducing particle size and size distribution of NPs, and the energy efficiency of orifice type HC-processed ECLK was two orders of magnitude than that of ultrasonic horn or high shear homogenization-processed ECLK. In vitro drug-release studies showed that the fabricated NPs had great potential as a drug delivery system. The observations of this study can offer strong support for HC to enhance the fabrication of size-controllable chitosan-genipin NPs.

Low-Temperature Cross-Linked Hole Transport Layer for High-Performance Blue Quantum-Dot Light-Emitting Diodes.

Quantum-dot light-emitting diodes (QLEDs), a kind of promising optoelectronic device, demonstrate potential superiority in next-generation display technology. Thermal cross-linked hole transport materials (HTMs) have been employed in solution-processed QLEDs due to their excellent thermal stability and solvent resistance, whereas the unbalanced charge injection and high cross-linking temperature of cross-linked HTMs can inhibit the efficiency of QLEDs and limit their application. Herein, a low-temperature cross-linked HTM of 4,4'-bis(3-(((4-vinylbenzyl)oxy)methyl)-9H-carbazol-9-yl)-1,1'-biphenyl (DV-CBP) with a flexible styrene side chain is introduced, which reduces the cross-linking temperature to 150 °C and enhances the hole mobility up to 1.01 × 10-3 cm2 V-1 s-1. More importantly, the maximum external quantum efficiency of 21.35% is successfully obtained on the basis of the DV-CBP as a cross-linked hole transport layer (HTL) for blue QLEDs. The low-temperature cross-linked high-mobility HTL using flexible side chains could be an excellent alternative for future HTL development.

A novel sponge composite of chitosan-sodium tripolyphosphate-melamine for anionic dye Orange II removal

Since the potential carcinogenic, toxic and non-degradable dyes trigger serious environmental contamination by improper treatment, developing novel adsorbents remains a major challenge. A novel high efficiency and biopolymer-based environmental-friendly adsorbent, chitosan‑sodium tripolyphosphate-melamine sponge (CTS-STPP-MS) composite, was prepared for Orange II removing with chitosan as raw material, sodium tripolyphosphate as cross-linking agent. The composite was carefully characterized by SEM, EDS, FT-IR and XPS. The influence of crosslinking conditions, dosage, pH, initial concentration, contacting time and temperature on adsorption were tested through batch adsorption experiments. CTS-STPP-MS adsorption process was exothermic, spontaneous and agreed with Sips isotherm model accompanying the maximum adsorption capacity as 948 mg∙g−1 (pH = 3). Notably, the adsorption performance was outstanding for high concentration solutions, with a removal rate of 97 % in up to 2000 mg∙L−1 OII solution (100 mg sorbent dosage, 50 mL OII solution, pH = 3, 289.15 K). In addition, the adsorption efficiency yet remained 97.85 % after 5 repeated adsorption-desorption cycles. The driving force of adsorption was attributed to electrostatic attraction and hydrogen bonds which was proved by adsorption results coupled with XPS. Owing to the excellent properties of high-effective, environmental-friendly, easy to separate and regenerable, CTS-STPP-MS composite turned out to be a promising adsorbent in contamination treatment.

Warm Pressing of Organosilicon Polymer Toward Monolithic Ceramics

Warm pressing of organosilicon polymers is often challenging due to the formation of cracks due to release of volatile compounds during the warm pressing process. The focus of the present study is to warm press crosslinked SMP‐10 powders into crack‐free compacts and to pyrolyze them to get bulk SiC monoliths. Crack formation during warm pressing is addressed by optimizing the crosslinking temperature, and the loss of formability of the powders crosslinked at higher temperatures is overcome with the use of uncured polymer as a binder. The crosslinking temperature of the preceramic polymer plays a crucial role in developing crack‐free green bodies. The amount of binder used is varied to study its effect on the bulk density of the pyrolyzed product. The warm pressed green bodies pyrolyzed at 1400 °C result in the formation of bulk silicon carbide ceramics and are characterized using X‐ray diffractometer and FTIR spectroscopy. Warm pressing is performed at a lower temperature than reported in the literature, and this limits the incorporation of oxygen during the warm pressing.

Photothermal Synergic Cross-Linking Hole Transport Layer for Highly Efficient RGB QLEDs.

Developing an insoluble cross-linkable hole transport layer (HTL) plays an important role for solution-processed quantum dots light-emitting diodes (QLEDs) to fabricate a multilayer device with separated quantum dots layers and HTLs. In this work, a facile photothermal synergic cross-linking strategy is simultaneous annealing and UV irradiation to form the high-quality cross-linked film as the HTL without any photoinitiator, which efficiently reduces the cross-linking temperature to the low temperature of 130 °C and enhances the hole mobility of the 3-vinyl-9-{4-[4-(3-vinylcarbazol-9-yl)phenyl]phenyl}carbazole (CBP-V) thin films. The obtained high-quality cross-linked CBP-V films exhibited smooth morphology, excellent solvent resistance, and high mobility. Moreover, the high-performance red, green, and blue (RGB) QLEDs are successfully fabricated by using the photothermal synergic cross-linked HTLs, which achieved the maximum external quantum efficiency of 25.69, 24.42, and 16.51%, respectively. This work presents a strategy of using the photothermal synergic cross-linked HTLs for fabrication of high-performance QLEDs and advancing their related device applications.

Overcoming the Trade-Off between Methanol Rejection and Proton Conductivity via Facile Synthesis of Crosslinked Sulfonated PEEK Proton Exchange Membranes

In this work, homogeneous, thin-film proton exchange membranes (PEMs) with superior proton conductivities and high methanol rejection were fabricated via a facile synthesis procedure. Sulfonated polyether ether ketone (sPEEK) was crosslinked via a Friedel–Crafts reaction by α,α′-dichloro-p-xylene, a non-hazardous and hydrophobic compound. PEMs with varying crosslinking and sulfonation degrees were fabricated to overcome the traditional trade-off between methanol rejection and proton conductivity. The sulfonation of PEEK at 60 °C for 24 h resulted in a sulfonation degree of 56%. Those highly sulfonated backbones, in combination with a low membrane thickness (ca. 20 µm), resulted in proton conductivities superior to Nafion 117. Furthermore, X-ray photoelectron spectroscopy proved it was possible to control the crosslinking degree via the crosslinking time and temperature. The PEMs with the highest crosslinking degree showed better methanol rejection compared to the commercial benchmark. The introduction of the crosslinker created hydrophobic membrane sections, which reduced the water and methanol uptake. Subsequently, the membrane became denser due to the crosslinking, hindering the solute permeation. Those two effects led to lower methanol crossovers. This study proved the successful fabrication of PEMs overcoming the trade-off between proton conductivity and methanol rejection, following a facile procedure using low-cost and non-hazardous materials.

Tailoring cross-linking temperature via hydrogen bonding and steric hindrance towards high-performance fire-Safe Polymer

Constructing thermally cross-linkable structures into thermoplastic polymers has emerged as a compelling strategy to enhance flame retardancy. However, the cross-linking reactions are hard to control, leading unexpected deterioration of processability and mechanical properties. Here, we report a novel strategy to modulate cross-linking reactions utilizing intramolecular hydrogen bonding and steric hindrance effects. Taking aromatic Schiff base (SA) as an example, novel monomers SAP and SAPN were designed and synthesized by incorporating phenolic and naphthalene units. As expected, the resultant copolymer PET-co-SAPNn exhibited a 120 °C higher cross-linking temperature compared with that of PET-co-SAn, powering them with great processability. Robust mechanical properties were obtained owing to the enhanced polymerization stability and intramolecular hydrogen bonding of SAPN, as evidenced by the tensile strength of 86.0 MPa for PET-co-SAPN15, 1.6 times to that of pure PET. Additionally, PET-co-SAPNn exhibits the highest fire safety, whose peak heat release rate (pHRR) and maximum smoke density (Dm) decreased by 49% and 53%, attributing to enhanced char-forming ability from the cross-linking and the phenolic and naphthalene units in SAPN. Considering these adequate improvements, this study provides a novel strategy for designing “self-cross-linking” flame-retardant polymers with improved processability and fire-safety.

Application of Biomaterials in the Development of Hydrogel-Forming Microneedles Integrated with a Cyclodextrin Drug Reservoir for Improved Pharmacokinetic Profiles of Telmisartan.

Telmisartan (TEL) is a promising antihypertensive agent among other angiotensin receptor blockers. However, its oral application is limited by its poor water solubility. This study presents the successful utilization of biomaterial-based hydrogel-forming microneedles integrated with a direct compressed tablet reservoir (HFMN-DCT) for the transdermal delivery of telmisartan in the treatment of hypertension. The combination of PVP, PVA, and tartaric acid was used in the HFMN formulation. A range of cross-linking temperatures and times were employed to optimize the characteristics of the HFMN. The HFMN exhibited excellent swelling capacity, mechanical strength, and insertion properties. Additionally, the poorly soluble characteristic of TEL was improved by the inclusion complex formulation with β-cyclodextrin (βCD). Phase solubility analysis showed an Ap-type diagram, indicating a higher-order complex between TEL and βCD, with respect to βCD. A ratio of TEL:βCD of 1:4 mM demonstrates the highest solubility enhancement of TEL. The inclusion complex formation was confirmed by FTIR, XRD, DSC, and molecular docking studies. A significantly higher release of TEL (up to 20-fold) from the inclusion complex was observed in the in vitro release study. Subsequently, a DCT reservoir was developed using various concentrations of sodium starch glycolate. Essentially, both the HFMN and DCT reservoir exhibit hemocompatibility and did not induce any skin irritation. The optimized combination of the HFMN-DCT reservoir showed an ex vivo permeation profile of 83.275 ± 2.405%. Notably, the proposed system showed superior pharmacokinetic profiles in the in vivo investigation using male Wistar rats. Overall, this study highlights the potential of HFMN-DCT reservoir systems as a versatile platform for transdermal drug delivery applications.