Polymer Network Research Articles

Investigating the Influence of the Substrate Temperature and the Organic Precursor on the Mechanical Properties of Low‐Pressure Plasma Polymer Films

ABSTRACTThis work aims to investigate the influence of the substrate temperature on low‐pressure plasma polymerization processes. Emphasis is placed on the mechanical properties and growth mechanism of the plasma polymer films (PPFs). For this purpose, two precursors are considered, differing only by their unsaturation degree: 2‐propen‐1‐ol (CH2═CH–CH2–OH) and propan‐1‐ol (CH3–CH2–CH2–OH). Although propan‐1‐ol‐based PPFs behave like hard elastic solids, 2‐propen‐1‐ol‐based coatings evolve from a liquid film to an elastic solid on increasing the substrate temperature. This behavior is understood considering the evolution of the glass transition temperature of PPFs. The latter is correlated with the cross‐linking degree of the polymeric network governed by the energy density of bombarding ions on the growing film.

Coating effect of polyurethane-layered double hydroxide nanocomposite on steel

The motivation behind this work is the preparation of polyurethane-magnesium aluminum layered double hydroxide (PU-LDH) nanocomposite and its application as a coating for steel protection. The coating was prepared with different doses of LDH, ranging from 0 to 2% of the coating weight. The effect of different concentrations on the mechanical, adhesion, and surface properties of PU coating is studied. Firstly, LDH was prepared via the coprecipitation process and then distributed in PU matrix. The nanocomposites were then crosslinked in the form of coating layers on steel. The preparation of the thermally stable crystalline LDH nanoparticles with 89 nm particle size was confirmed by FTIR, XRD, DLS, and TGA. SEM photos showed the dispersed and intercalated structure. The coating characteristics demonstrate that addition of LDH decreased the drying time and increased the dry film thickness of PU up to 1.5% due to the crosslinking between the large surface area nanofiller and polyurethane matrix. Furthermore, the prepared LDH nanofiller increased the adhesion strength, impact resistance, abrasion resistance, modulus, and flexibility of PU due to the strong polymeric network structure. The 2% nanocomposite coating shows poor properties due to the excess concentration and heterogeneous dispersion of nanoparticles within the PU polymer. The resistance to fire and some chemicals was supported by the thermally and physically stable LDH nanoclay. The former characterizations state that the proposed PU-LDH nanocomposite is an enhanced and applicable coating.

Cu(II)-Organic Coordination Polymer Networks for Persistent Nitric Oxide Release in Tumor Therapy.

Nitric oxide (NO) plays a key role in regulating the immune system by polarizing macrophages toward the proinflammatory M1 phenotype, which is beneficial for cancer immunotherapy. We developed a Cu-organic coordination polymer network to sustainably release NO from endogenous donors. This robust polymer network was constructed through a dual-interaction process: complexation and cross-linking. The carboxylate groups of deprotonated 4-((6-(acryloyloxy)hexyl)oxy)benzoic acid (BA) served as bidentate ligands for the formation of Cu(II) complexes. The acrylate moiety of BA anchored these complexes in the polymer network, forming a cross-linked film. Cu ions within the network catalytically promoted NO release from S-nitrosoglutathione, maintaining this release even after 90 days in a physiological environment. The released NO effectively polarized both resting (M0) and tumor-promoting (M2) macrophages to the M1 phenotype. With their demonstrated physiological stability and sustained NO release performance, BA-Cu films hold potential as anticancer patches capable of continuously promoting antitumoral macrophages.

Flexible and antibacterial conductive hydrogels based on silk fibroin/polyaniline/AgNPs for motion sensing and wound healing promotion under electrical stimulation.

Flexible conductive hydrogel-based electronic skin (E-skin) for simultaneous biotherapeutics and sensing applications is one of the current research directions. In this study, conductive and homogeneous silk fibroin/polyaniline/AgNP complexes (SPAg complexes) were prepared with the assistance of silk fibroin, which greatly optimized the compatibility of PANI with the hydrogel matrix. Then, SPAg was introduced into the covalently crosslinked polymer network to prepare poly(acrylamide-co-sulfobetaine methacrylate) - SPAg hydrogels (labeled as PSPAg hydrogels). The PSPAg hydrogels exhibit good biocompatibility, excellent mechanical properties, superb adhesive performance, and fantastic sensing capabilities. Being connected to a smartphone via a Bluetooth system, the SPAg hydrogel-based E-skin was employed to accurately monitor human movements including vigorous joint movements and subtle facial micro-expressions. Finally, benefiting from the synergistic effect of antimicrobial and exogenous electrical stimulation, through promoting angiogenesis and accelerating collagen production in diabetic wounds, PSPAg E-skin successfully facilitates rapid diabetic wound healing. Therefore, the multifunctional PSPAg hydrogel-based E-skin shows great promise for applications in wearable devices and bioelectronics.

Injectable and 3D Extrusion Printable Hydrophilic Silicone-Based Hydrogels for Controlled Ocular Delivery of Ophthalmic Drugs.

While silicone elastomers have found widespread use in the biomedical industry, 3D printing them has proven to be difficult due to the material's slow drying time, low viscosity, and hydrophobicity. Herein, we arrested the hydrophilic silicone (HS) macrochains into a semi-interpenetrating polymer network (semi-IPN) via an in situ photogelation-assisted 3D microextrusion printing technique. The flow behavior of the pregel solutions and the mechanical properties of the printed HS hydrogels were tested, showing a high elastic modulus (approximately 15 kPa), a low tan δ, high elasticity, and delayed network rupturing. The uniaxial compression tests demonstrated a nearly negligible permanent deformation, suggesting that the printed hybrid hydrogel maintained its elastic properties. Drug loading and diffusion in the microporous hydrogel are shown via the non-Fickian anomalous transport mechanism, leading to highly tunable loading/releasing profiles (approximately 20% cumulative release) depending on the HS concentration. The drug encapsulation exhibits exceptional stability, remaining intact without any degradation even after a storage period of 1 month. As far as we know, this is the first soft biomaterial based on HS that functions as an exceptional controlled drug delivery device.

Enhancement on the thermal and tribological behaviors of polyurethane/epoxy-based interpenetrating network composites by orientationally aligned CNF/MXene/WPU aerogels

Tribological behaviour of polyurethane/epoxy interpenetrating polymer network (PU/EP IPN) as friction materials was investigated. This was a combination of the good flexibility of PU and high hardness of EP to realize polymer synergistic effect of interpenetrating network structure, aiming to broaden and develop the application of polymer-based composites in friction engineering materials. A novel CNF/MXene/WPU aerogel (CMW) was prepared by employing flexible NCO-terminated waterborne polyurethane prepolymer (WPU) as the supporting skeleton of aerogel, and synchronously combining the reinforcing-phase carbon nanofibers (CNF) and lubricating-phase MXene. Subsequently, the prepared ultralight porous yet mechanically robust CMW aerogels were encapsulated with IPN by vacuum impregnation. As expected, the addition of aerogel imparted IPN matrix with enhanced thermal and tribological properties due to the thermal dispersion and enhancement effects conferred on the matrix by the highly aligned and ordered three-dimensional interconnected structure of aerogel. Meanwhile, CMW reinforced IPN composites were explored for the formation of a high-quality transfer film on the contact surface during friction. The transfer film prevented direct contact between the friction couples, which facilitated the improvement of wear resistance of composites, thus giving this material great potential for tribological applications.

Facile fabrication of robust and tight PIMs-based TFC hollow fiber membranes with a semi-interpenetrating polymer network via liquid phase cross-linking for organic solvent nanofiltration

Resource recovery and reuse are essential for sustainable development, particularly for high-value resources such as homogeneous (photo)catalysts, active pharmaceutical ingredients, and high-value natural compounds, which can offer economic benefits. Recently, organic solvent nanofiltration (OSN) for resource recovery has gained significant attention owing to its advantages including low energy consumption and seamless integration with other processes. Polymers of intrinsic microporosity (PIMs) have great potential as membrane materials for OSN, owing to their excellent pore properties and solution processability. However, swelling and dissolution of PIMs in organic solvents can impede the filtration performance of PIMs-based OSN membranes. In this study, we fabricated thin-film composite hollow fiber membranes for OSN based on PIMs with improved organic solvent stability using a semi-interpenetrating polymer network (semi-IPN) formed by cross-linking Matrimid with 1,6-hexanediamine within the PIMs through the liquid phase cross-linking method. Semi-IPNs mitigate swelling and tighten the pores of PIMs-based membranes, enabling excellent filtration and molecular separation performance. Furthermore, the fabricated PIMs with a semi-IPN membrane exhibited excellent rejection performance (>96 %) for homogeneous photocatalysts, allowing successful concentration and recovery via OSN. Therefore, PIMs-based membranes with a semi-IPN hold great promise as OSN membranes for the recovery of valuable resources.

Fast-response and high figure of merit phase shifter based on polymer- stabilised liquid crystals

ABSTRACT This article presents a novel fast-response and high figure of merit (FoM) phase shifter based on polymer-stabilised liquid crystal (LC) for Ka-band. The developed LC phase shifter (LCPS), utilising a coplanar differential line loading 19 parallel-plate variable capacitors with 4.6 μm LC-cell, adopts polymer-stabilised LC technology in which the parallelly orientated polymer networks facilitate the LC molecules’ return to their initial state upon removal of the bias voltage, thus accelerating response time. The proposed LCPS has been fabricated to evaluate its superior capabilities. The experimental results closely match the simulation results, confirming its good congruity. This design has measured S 11 < −10 dB in 29–31 GHz. LCs with different HCM002 concentrations are injected to LCPS, and the experimental outcomes showed that LCs with 9 wt% HCM002 concentration significantly improve the response time of LCPS to 2.8 ms with a high FoM of 91.2°/dB at 30 GHz.

A Recyclable Ionogel with High Mechanical Robustness Based on Covalent Adaptable Networks.

Ionogels are an emerging class of soft materials for flexible electronics, with high ionic conductivity, low volatility, and mechanical stretchability. Recyclable ionogels are recently developed to address the sustainability crisis of current electronics, through the introduction of non-covalent bonds. However, this strategy sacrifices mechanical robustness and chemical stability, severely diminishing the potential for practical application. Here, covalent adaptable networks (CANs) are incorporated into ionogels, where dynamic covalent crosslinks endow high strength (11.3MPa tensile strength), stretchability (2396% elongation at break), elasticity (energy loss coefficient of 0.055 at 100% strain), and durability (5000 cycles of 150% strain). The reversible nature of CANs allows the ionogel to be closed-loop recyclable for up to ten times. Additionally, the ionogel is toughened by physical crosslinks between conducting ions and polymer networks, breaking the common dilemma in enhancing mechanical properties and electrical conductivity. The ionogel demonstrates robust strain sensing performance under harsh mechanical treatments and is applied for reconfigurable multimodal sensing based on its recyclability. This study provides insights into improving the mechanical and electrical properties of ionogels toward functionally reliable and environmentally sustainable bioelectronics.

Polymers from renewable resources: Challenge of conventional thermoset materials and the need for sustainable thermoset polymers

Polymers from renewable resources: Challenge of conventional thermoset materials and the need for sustainable thermoset polymers

Fabrication of plasticized interpenetrating polymer network (IPN) leatherette derived from bacterial cellulose and silicon dioxide using a novel 2-in-1 thickening process

Fabrication of plasticized interpenetrating polymer network (IPN) leatherette derived from bacterial cellulose and silicon dioxide using a novel 2-in-1 thickening process

Tailorable MBene aerogel with the lowest evaporation enthalpy for solar seawater desalination and wastewater purification

Growing global water scarcity has fueled the quest for sustainable and effective desalination solutions under lower energy requirements. However, it has a common strategy that has led to reducing the enthalpy of evaporation of water during solar-driven interfacial evaporation by dual-layer aerogels with effective mechanical robustness. Here, we introduce a novel class of 2D transition metal boride (MBene) integrated into the hydratable polymeric network of Polyvinyl alcohol/Chitosan/Polyurethane (MPCP) for an “all-in-one” solar evaporator. This dual-layer aerogel possesses both photothermal properties (for evaporating seawater) and reduced evaporation enthalpy (resulting in lower energy requirements). The MPCP aerogel gains broadband light absorption, and effective heat localization and exploits the polar groups on the polymer chains to interact with water molecules, resulting in reduced enthalpies of evaporation of 1132 J g−1 for water and 1245 J g−1 for seawater, which promotes excellent solar steam generation performance with a high evaporation rate of 2.83 kg/m2h under 1 kW m−2 solar intensity. The MBene aerogel has favorable endurance and versatility in effectively treating a wide range of polluted wastewater sources, such as organic dyes and heavy metal solutions, with high efficiency and exceptional longevity under real seawater tests over 20 consecutive days. This work could guide the development of MBenes for efficient solar-driven water evaporation and wastewater remediation.

Hydrotalcite-Enhanced Tough and Strong Hydrogel Endowed by Coordination and Electrostatic Interactions for Both Strain and Pressure Sensors.

Polymer hydrogels have a wide range of applications in the field of flexible wearable devices from the perspective of easy commercialization and environmental compatibility. However, traditional hydrogels often fail to achieve adequate mechanical strength and performance such as toughness, resilience, and ionic conductivity. Herein, a significant enhancement of tensile strength in 2 orders of magnitude (from 36 kPa to 1.5 MPa) is obtained by the introduction of hydrotalcite into polymer network via multiple, multilevel, and strong interactions of strengthened interface interactions, and the enhancement effect is superior to most of known records. Meanwhile, the enhanced conductivity may be rationally attributed to effective channels of hydrotalcite for ion transport. As a result, high toughness (9.5 MJ/m3), stretchability (1520%), excellent resilience (100% rebound of 400% strain), high conductivity (2.6 mS/cm), and low-temperature resistance are successfully achieved. The work shows an efficient approach to design desired ultratough and multifunctional hydrogels.

Exploiting Lignin Structure and Reactivity to Design Vitrimers with Controlled Ratio of Dynamic to Non-Dynamic Bonds.

Lignin is an abundant biobased feedstock, representing the first source of renewable aromatic structures. Thanks to its high functionality in aliphatic hydroxyls (Al-OH), phenolic hydroxyls (Ph-OH) and carboxylic acids (COOH), lignin is an attractive precursor to crosslinked polymer materials. Different biobased macromolecular architectures can be designed from lignins, whose end-of-life should also be considered in the context of a circular bioeconomy. To enhance recyclability of crosslinked polymer networks, the introduction of dynamic linkages to design vitrimers is a promising strategy. In this study, Kraft lignin was chemically modified with succinic anhydride, to prepare a series of modified lignins with a controlled COOH/Ph-OH ratio, exploiting the difference in reactivity between Al-OH and Ph-OH groups. Upon crosslinking with a diepoxy, mixed vitrimer networks with variable ratios between dynamic ester bonds and non-dynamic ether bonds were synthesized. The analysis of their properties evidenced the impact of the non-dynamic linkages on the materials behaviors, including their dynamicity and reprocessing ability. Although the activation energy for bond exchange is increased, non-dynamic linkages do not hinder the reprocessability of these adaptable materials, and provide them high creep resistance. The controlled introduction of non-dynamic linkages appears as a promising strategy to enhance the properties of lignin-based vitrimers.

The effect of dynamic cross-links and mesogenic groups on the swelling and collapse of polymer gels

The polymer gels containing dynamic cross-links and mesogenic groups are among the key candidates for the development of soft actuators and detectors, displays, sensors and other programmable and self-healing materials. In this article, firstly, the collapse of polymer networks with irreversible cross-links in the presence of a dynamic cross-linker is investigated by means of Flory-type theory. It is shown that, at not a very poor solvent quality (near the theta-conditions), the swelling ratio for a gel containing irreversible and dynamic cross-links is less than for a gel with irreversible cross-links only, whereas at poor or good solvent qualities sizes of these gels are close to each other. The number of dynamic cross-links monotonically increases with worsening the solvent quality. The gel contraction can be also achieved by increasing the dynamic cross-linker concentration, which allows one to change the transition point in a wide range of solvent conditions. Secondly, polymer networks containing irreversible and dynamic cross-links and incorporating mesogenic side groups is studied using the Maier–Saupe theory. With decreasing in the temperature, the continuous transition from a swollen to collapsed state occurs. With further increase in the temperature, the swelling ratio discontinuously decreases and the nematic order parameter sharply increases from zero to a value ​​close to one. By increasing the dynamic cross-linker concentration, the swelling-to-collapse transition and, then, the isotropic-nematic transition are observed. A phase diagram of the gel is constructed and, depending on the dynamic cross-linker concentration and temperature, the swollen gel with the zero nematic order parameter, the collapsed gel with the zero nematic order parameter, and the collapsed gel with the nematic ordering can be formed. A growth of the length of the mesogenic side group leads to an increase in the area of ​​existence of the collapsed gel with the nematic ordering in the phase diagram. The obtained theoretical results are in agreement with corresponding experimental data from the literature.

Synergistic effects of starch and carrageenan from Kappaphycus alvarezii in composite film formation: Physicochemical and degradable properties

Rising concerns around plastic pollution from single-use plastic (SUPs), especially food packaging, have driven interest in sustainable alternatives. As such, algae biomass has gained attention for bioplastic production due to algae's rapid growth and abundant polysaccharides. This research focuses on extracting carrageenan from Kappaphycus alvarezii, extensively cultivated in Sabah, Malaysia, and utilizing it in combination with starch and glycerol to develop algae-based films. The physicochemical properties and degradation rate of these films were evaluated, revealing that the addition of carrageenan enhanced overall thermal stability meanwhile increasing water solubility, water content but reducing the degradation rate and swelling degree. This is primarily due to the crystalline structures of carrageenan, which provide a more rigid arrangement compared to the network of starch polymers. However, the incorporation of starch into the blends has enhanced the elongation and surface morphology, resulting in more balanced properties. Overall, these carrageenan films displayed impressive thermal, mechanical, and biodegradability characteristics, establishing their viability as substitutes for conventional plastics.

Impact of Reversible Deactivation Radical Copolymerizations (RDRPs) on Gelation, Phase Separation, and Mechanical Properties of Polymer Networks

Impact of Reversible Deactivation Radical Copolymerizations (RDRPs) on Gelation, Phase Separation, and Mechanical Properties of Polymer Networks

Influence of Rheological Modifications on Primary Network Chemical and Structural Cure Kinetics for an Interpenetrating Polymer Network Resin.

The development of non-contact in situ techniques for monitoring cure kinetics has the potential to greatly improve both resin formulation and processing. We have recently shown that low-frequency Raman spectroscopy is a viable method for assessing resin structural cure kinetics and complements the traditional chemical conversion determined from the fingerprint region of the spectrum. In this work, we further evaluate the relationship between structural and chemical conversion by investigating two chemically identical yet rheologically different interpenetrating polymer network resin formulations. Rheological analysis demonstrates a relationship between structural conversion and storage modulus, which is not observed in the chemical conversion data. We show that one can produce master cure kinetics curves with comparable kinetic constants using both the chemical and structural conversion methodologies. Parametric analysis of the structural conversion, chemical conversion, and photorheological conversion was combined with a semi-empirical model for the storage shear modulus as a function of the extent of cure.

Adhesive and cohesive fracture of blood clots: Experiments and modeling

Blood clots represent living materials composed of a polymer network and an abundance of cells. They might fracture within the bulk material of the clot (cohesive fracture), at the interface between the clot and the surrounding tissue (adhesive fracture), or through a combination of both modes (hybrid fracture). The clot fracture within vascular systems and injury sites could lead to life-threatening conditions. Despite the significance, understanding and modeling the fracture behaviors of blood clots, including their dependence on mechanical loading and cellular components, remain in a nascent stage. In this study, we employ an integrated experimental-computational approach to comprehensively investigate the fracture behaviors of bovine blood clots. We explore various mechanical factors, substrates, and cellular components such as red blood cells (RBCs) and platelets. Our findings reveal that among various tissue substrates, blood clots exhibit the highest interfacial adhesion energy with muscle, and the lowest to the inner arterial lining, consistent with their biological function. Both interfacial adhesion energy and bulk fracture energy are rate-dependent, although they exhibit different dependencies. Also, RBCs and platelets have different effects on clot fracture. An increase in RBC content tends to toughen both adhesion and fracture of blood clots. However, an increase in platelet content enhances interfacial adhesion energy but lowers the bulk fracture energy. The platelet content also governs the shift from adhesive fracture to hybrid fracture. To model clot fracture, we developed two finite element models incorporating a coupled cohesive-zone and Mullins-effect approach to simulate pure shear fracture and peeling of blood clots. These models, validated through experimental data, elucidate the interplay between intrinsic fracture toughness, interfacial strength, and bulk energy dissipation during clot fracture. This study significantly advances our understanding of clot mechanics, providing valuable insights into the mechanics of similar living materials and the management of clot-related disorders such as hemorrhage and thrombosis.

An Investigation into Mechanical Properties of 3D Printed Thermoplastic-Thermoset Mixed-Matrix Composites: Synergistic Effects of Thermoplastic Skeletal Lattice Geometries and Thermoset Properties.

This study aims to develop thermoplastic (TP) and thermoset (TS) based mixed matrix composite using design dependent physical compatibility. Using thermoplastic-based (PLA) skeletal lattices with diverse patterns (gyroid and grid) and different infill densities (10% and 20%) followed by infiltration of two different thermoset resin systems (epoxy and polyurethane-based) using a customized FDM 3D printer equipped with a resin dispensing unit, the optimised design and TP-TS material combination was established for best mechanical performance. Under uniaxial tensile stress, the failure modes of TP gyroid structures with polyurethane-based composites included 'fiber pull-out', interfacial debonding and fiber breakage, while epoxy based mixed matrix composites with all design variants demonstrated brittle failure. Higher elongation (higher area under curve) was observed in 20% infilled gyroid patterned composite with polyurethane matrix indicating the capability of operation in mechanical shock absorption application. Electron microscopy-based fractography analysis revealed that thermoset matrix properties governed the fracture modes for the thermoplastic phase. This work focused on the strategic optimisation of both toughness and stiffness of mixed matrix composite components for rapid fabrication of construction materials.