Dry State Research Articles

Molecular Dynamics Simulation and Experimental Study of Friction and Wear Characteristics of Carbon Nanotube-Reinforced Nitrile Butadiene Rubber

Nitrile butadiene rubber (NBR) and its various composite materials are widely employed as friction materials in mechanical equipment. The use of carbon nanotube (CNT) reinforcement in NBR for improved friction and wear characteristics has become a major research focus. However, the mechanisms underlying the improvement in the friction and wear characteristics of NBR with different CNT contents remain insufficiently elucidated. Therefore, we conducted a combined analysis of NBR reinforced with varying CNT contents through molecular dynamics (MD) simulations and ring–block friction experiments. The aim is to analyze the extent to which CNTs enhance the water-lubricated friction and dry wear properties of NBR and explore the improvement mechanisms through molecular chain characteristics. The results of this study demonstrate that as the mass fraction of CNTs (0%, 1.25%, 2.5%, 5%) increases, the water-lubricated friction coefficient of NBR continuously decreases. Under water-lubricated conditions, CNTs improve the water storage capacity of the NBR surface and enhance lubrication efficiency. In the dry wear state, CNTs help reduce scratch depth and dry wear volume.

Preparation and Mechanism of Shale Inhibitor TIL-NH2 for Shale Gas Horizontal Wells

In this study, a new polyionic polymer inhibitor, TIL-NH2, was developed to address the instability of shale gas horizontal wells caused by water-based drilling fluids. The structural characteristics and inhibition effects of TIL-NH2 on mud shale were comprehensively analyzed using infrared spectroscopy, NMR spectroscopy, contact angle measurements, particle size distribution, zeta potential, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The results demonstrated that TIL-NH2 significantly enhances the thermal stability of shale, with a decomposition temperature exceeding 300 °C, indicating excellent high-temperature resistance. At a concentration of 0.9%, TIL-NH2 increased the median particle size of shale powder from 5.2871 μm to over 320 μm, effectively inhibiting hydration expansion and dispersion. The zeta potential measurements showed a reduction in the absolute value of illite’s zeta potential from −38.2 mV to 22.1 mV at 0.6% concentration, highlighting a significant decrease in surface charge density. Infrared spectroscopy and X-ray diffraction confirmed the formation of a close adsorption layer between TIL-NH2 and the illite surface through electrostatic and hydrogen bonding, which reduced the weakly bound water content to 0.0951% and maintained layer spacing of 1.032 nm and 1.354 nm in dry and wet states, respectively. Thermogravimetric analysis indicated a marked reduction in heat loss, particularly in the strongly bound water content. Scanning electron microscopy revealed that shale powder treated with TIL-NH2 exhibited an irregular bulk shape with strong inter-particle bonding and low hydration degree. These findings suggest that TIL-NH2 effectively inhibits hydration swelling and dispersion of shale through the synergistic effects of cationic imidazole rings and primary amine groups, offering excellent temperature and salt resistance. This provides a technical foundation for the low-cost and efficient extraction of shale gas in horizontal wells.

Experimental and numerical estimation of thermal conductivity of bio-based building composite materials with an enhanced thermal capacity

The paper tackles the important problem of estimating and predicting the thermal conductivity of bio-based building materials that can help decarbonize the building sector. Knowledge and the possibility to optimize their insulating properties is the first criterion for determining the ability of their use in the building sector. The novel yet not well-studied hemp shives and magnesium binder composites with improved thermal mass by microencapsulated phase change material (PCM) were considered. The samples of composites without PCM having different densities as well as with different amounts of microencapsulated PCM and the same density were manufactured and tested experimentally in different states, i.e., dry and after conditioning at relative humidity (RH) of 50, 75, and 90 %, and in the case of samples with PCM also at different average measurement temperatures selected with respect to the phase change range of the PCM. A novel method of predicting bio-based composites' effective thermal conductivity tensor was also developed. The method is based on the numerical solution of the heat conduction equation at the micro-scale considering real composite microstructure. The method was tuned using micro-computed tomography (μCT) data with the microstructure of composites without PCM and then applied to predict the thermal conductivities of composites with PCM, utilizing computational domains with an artificially distributed PCM in the binder. The experimental testing of composites without PCM revealed an apparent effect of increasing thermal conductivity with rising sample density and RH applied during conditioning. With an increase in density from 394 to 576 kg/m3, their thermal conductivities varied from 0.105 to 0.159 W/m/K for the dry state and from 0.157 to 0.241 W/m/K for RH 90 %. A similar effect of sample state and RH was observed for composites with microencapsulated PCM, which had the highest thermal conductivity, equal to 0.265 W/m/K, for the lowest PCM amount and RH 90 %. Moreover, a decrease in composites' effective thermal conductivity with an increase in PCM fraction was observed, except for the lowest PCM fraction, for which it increased. It also rose with increasing the average measurement temperature. The developed micro-scale-based numerical method allowed for predicting the thermal conductivities of composites with accuracies below 4.1 and 7.2 % for composites without and with PCM, respectively, except for the composite with the lowest amount of PCM, which behaved differently. Thus, its suitability for designing and optimizing bio-based composites was shown.

Ultra-adherable dual-network conductive hydrogel with moistening and anti-freezing as a flexible sensor

Multifunctional conductive hydrogels have shown great promise in wearable flexible sensor application. This paper reported a dual-network self-healing electrically hydrogel through simple one-pot polymerization, which initiated from Ag+- lignin nanoparticles (LNPs) -APS redox system. Owing to the reversible metal coordination and hydrogen bonding cross-linked among polymer network, the resulting conductive hydrogel-based sensor demonstrated excellent stretchable, adhesion strength, and fatigue resistance. Additionally, the complex hydrogel (PHEMA/SA/Gly/Ca) incorporating with glycerol and CaCl2 in particular exhibited strong frost resistance (−40oC) and moisturizing qualities to monitor the motion signals in the low-temperature dry state. Therefore, the fabricated wearable sensor is sufficient for detecting large and small human motions, suggesting lots of promising applications in electronic skins, information identification and encryption, and human-motion monitoring.

In vitro biocompatibility analysis of protein-resistant amphiphilic polysulfobetaines as coatings for surgical implants in contact with complex body fluids

The fouling resistance of zwitterionic coatings is conventionally explained by the strong hydrophilicity of such polymers. Here, the in vitro biocompatibility of a set of systematically varied amphiphilic, zwitterionic copolymers is investigated. Photocrosslinkable, amphiphilic copolymers containing hydrophilic sulfobetaine methacrylate (SPe) and butyl methacrylate (BMA) were systematically synthesized in different ratios (50:50, 70:30, and 90:10) with a fixed content of photo-crosslinker by free radical copolymerization. The copolymers were spin-coated onto substrates and subsequently photocured by UV irradiation. Pure pBMA and pSPe as well as the prepared amphiphilic copolymers showed BMA content-dependent wettability in the dry state, but overall hydrophilic properties a fortiori in aqueous conditions. All polysulfobetaine-containing copolymers showed high resistance against non-specific adsorption (NSA) of proteins, platelet adhesion, thrombocyte activation, and bacterial accumulation. In some cases, the amphiphilic coatings even outperformed the purely hydrophilic pSPe coatings.

Polyurethane Based Smart Composite Fabric for Personal Thermal Management in Multi-Mode.

Textiles with thermal/moisture managing functions are of high interest. However, making the textile sensitive to the surrounding environment is still challenging. Herein, a multimodal smart fabric is developed by stitching together the Ag coated thermal-humidity sensitive thermoplastic polyurethane (Ag-THSPU) and the hybrid of polyvinylidene fluoride and polyurethane (PU-PVDF). The porous PU-PVDF layer is used for solar reflection, infrared emissivity, and water resistance. The Ag-THSPU layer is designed for regulating thermal reflection, sweat evaporation as well as convection. In cold and dry state, the Ag domains are densely packed covering the crystalline polyurethane matrix, featuring low water transmission (102.74gm-2·24h-1), high thermal reflection and 2.4°C warmer than with cotton fabric. In the hot and humid state, the THSPU layer is swollen by sweat and expands in area, resulting in the formation of micro-hook faces where the Ag domains spread apart to promote sweat evaporation (2084.88g/m-2·24h-1), thermal radiation and convection, offering 2.5°C cooler than with cotton fabric. The strategy reported here opens a new door for the development of adaptive textiles in demanding situations.

Effect of acetylation on wood-water interactions studied by sorption calorimetry

AbstractSorption of water has a profound effect on the material properties of wood. The uptake of water vapour in wood and other materials releases more heat than the condensation of vapour to liquid water. This excess energy provides insights to the interactions and energy state of the absorbed water molecules. Modification of wood by acetylation is a common way of altering the wood-water interactions; however, very few data exist on how this and other types of modification affect the energy state of absorbed water in wood. This study is the first to use sorption calorimetry on modified wood to explore the effect of acetylation on wood-water interactions. Acetylation decreased the strength of the interactions between wood and water as seen from a decrease in differential enthalpy of mixing, both overall and in the dry state. It appears that acetylation removes or hinders the most-energetic interactions or bonding configurations of water in wood, perhaps because acetylation reduces the number of water-accessible hydroxyls more than it reduces the amount of absorbed water molecules.

Study on the Influence of Temperature and Water Content on the Static Mechanical Properties of Sandstone

The area of permafrost worldwide accounts for approximately 20% to 25% of land area. In cold-climate regions of China, which are garnering international attention, the study of low-temperature and moisture effects on rock mass mechanical properties is of significant importance. China has a wide area of cold regions. This research can provide a foundation for China’s exploration activities in such extreme environments. This paper examines the mechanical behavior of rock specimens subjected to various low temperatures and water contents through uniaxial compression tests. The analysis encompasses failure modes, stress–strain relationships, uniaxial compressive strength (UCS), and elastic modulus (EM) of these specimens. Findings reveal that at lower temperatures, the rock specimens’ fracture patterns transition from compressive shear failure to cleavage failure, reflecting a shift from a plastic–elastic–plastic to a plastic–elastic response. Specifically, saturated rocks exhibit a 40.8% decrease in UCS and an 11.4% reduction in EM compared to their dry counterparts. Additionally, in cold conditions, an increased water content in rocks primarily leads to vertical cracking. Under such conditions, saturated rocks show a 52.3% decline in UCS and a 15.2% reduction in EM, relative to their dry state.

Gas Cluster Ion Beam-Assisted Deposition for Fabricating Dry Multilayers Containing Enzyme and Substrate with On-Demand Release.

Gas cluster ion beam (GCIB)-assisted deposition is used to build multilayered protein-based structures. In this process, Ar3000-5000+ clusters bombard and sputter molecules from a reservoir (target) to a collector, an operation that can be sequentially repeated with multiple targets. The process occurs under a vacuum, making it adequate for further sample conservation in the dry state, since many proteins do not have long-term storage stability in the aqueous state. First of all, the stability in time and versatility in terms of molecule selection are demonstrated with the fabrication of peptide multilayers featuring a clear separation. Then, lysozyme and trypsin are used as protein models to show that the activity remaining on the collector after deposition is linearly proportional to the argon ion dose. The energy per atom (E/n) of the Ar clusters is a parameter that was also changed for lysozyme deposition, and its increase negatively affects activity. The intact detection of larger protein molecules by SDS-PAGE gel electrophoresis and a bioassay (trypsin at ≈25 kDa and glucose oxidase (GOx) at ≈80 kDa) is demonstrated. Finally, GOx and horseradish peroxidase, two proteins involved in the same enzymatic cascade, are successively deposited on β-d-glucose to build an on-demand release material in which the enzymes and the substrate (β-d-glucose) are combined in a dry trilayer, and the reaction occurs only upon reintroduction in aqueous medium.

Thermal Effusivity Assessment of Sportswear Fabrics in the Dry State: Stacked and Air-Hoop Methods

Abstract In recent years, thermal effusivity, a property that describes the warm or cool touch perception, has gained significant attention in the apparel industry as it contributes to human thermophysiological comfort. The current study aims to explore the thermal effusivity of 27 sportswear fabrics, including woven and knitted structures with various fiber contents, using the stacked method (according to ASTM D7984-21, Standard Test Method for Measurement of Thermal Effusivity of Fabrics Using a Modified Transient Plane Source (MTPS) Instrument) and a modified air-hoop method. The results obtained revealed that the pressure range specified in ASTM D7984-21 (10–50 kPa) may cause fabric compression, resulting in the measurement of a material-based thermal effusivity rather than the fabric thermal effusivity. A pressure of 1 kPa was found to be more appropriate for obtaining accurate measurements of sportswear fabrics without altering their three-dimensional structure. Furthermore, a strong correlation was observed between the stacked and air-hoop methods for fabrics with thicknesses close to or greater than 0.4 mm. The air-hoop method simulates the configuration when the fabric is worn as part of a garment. The new knowledge provided by this research will enhance the accuracy of the thermal effusivity measurement of sportswear fabrics. It will contribute to the development of more comfortable fabrics considering realistic garment use scenarios.

Microstructure and properties of Ni20Cr–MoS2 composite coating by subsonic flame spraying

In this study, a Ni20Cr–MoS2 composite coating was fabricated using subsonic flame-spraying technology, and the effects of adding MoS2 on the microstructure, mechanical properties, and tribological properties of the coating were studied. The microstructure analysis of the coatings revealed that the Ni20Cr and Ni20Cr-MoS2 coatings prepared by subsonic flame spraying had fewer microscopic defects and significant particle flattening. After the addition of MoS2, the porosity of the coating decreased, whereas its microhardness increased. The cohesive strength of the coating was measured using the scratch method, and it was found to be enhanced after the addition of MoS2. Moreover, in the dry friction state, compared with the Ni20Cr coating, the Ni20Cr–MoS2 coating performs better. At a load of 20 N, the friction and wear performances of the Ni20Cr–MoS2 coating were the best, and the friction coefficient decreased by 11.63 %. Based on this, the relationships between the cohesive strength and tribological properties and between the wear mechanism and scratch mechanism of the coating are discussed.

Misleading Pore Size Measurements in Gelatin and Alginate Hydrogels Revealed by Confocal Microscopy.

It is a well-documented phenomenon that the porous structure of hydrogels observed with vacuum-based imaging techniques is generated during the freezing and drying process employed prior to observation. Nevertheless, vacuum-based techniques, such as scanning electron microscopy (SEM), are still being commonly used to measure pore sizes in hydrogels, which is often not representative of the actual pore size in hydrated conditions. The frequent underestimation of the impact of freezing and drying on hydrogel structures could stem from a lack of cross-fertilization between materials science and biomedical or food science communities, or from the simplicity and visually appealing nature of SEM imaging, which may lead to an overemphasis on its use. Our study provides a straightforward and impactful way of pinpointing this phenomenon exploiting two hydrogels ubiquitously applied in tissue engineering, including gelatin methacryloyl and alginate as proof-of-concept hydrogels. By comparing images of the samples in the native hydrated state, followed by freezing, freeze-drying, and rehydration using SEM and confocal microscopy, we highlight discrepancies between hydrogel pore sizes in the hydrated versus the dry state. To conclude, our study offers recommendations for researchers seeking insight in hydrogel properties and emphasizes key factors that require careful control when using SEM as a characterization tool.

Experimental investigation on the anisotropy of friction property for dry and water-saturated rock

Friction properties of rock are closely connected with the anisotropy. The anisotropy of rock friction can provide a valuable assessment for geotechnical and geological engineering. In this study, the rotary friction tests were conducted to analyze the water effect on the friction property and the friction anisotropy of the four types of rock. The drilling response model (DD-model) was employed to characterize the rotary friction behavior of the rocks. The parameters of this model include the three types of friction parameters: 1/ς, μ, and f, where 1/ς and μ are constant, and f is a variable. A quantitative method is proposed for assessing the anisotropy of rock friction. The results of the rotary friction tests indicate that the relation between torque force and thrust force conforms to the DD-model. The changes of two friction constants 1/ς and μ from dry state to water-saturated state suggest that the water effect on the friction strength of the rocks exhibits significant anisotropy. The friction strength determined by the friction variable f increases first, then decreases, and finally stabilizes with the increasing of depth. AIf is an anisotropy index calculated by the proposed method. The percentage difference of the average value of AIf between water-saturated and dry states shows the degree of the water effect on the friction anisotropy of the rocks, mudstone (MU) > granite (GR) > fine sandstone (FS) > argillaceous siltstone (AS). The quantitative model is hopefully constructed for characterizing the relation between the anisotropic friction strength of rock and the moisture state in future.

Influence of Immersion Time on the Frequency Domain Characteristics of Acoustic Emission Signals in Clayey Mineral Rocks.

The frequency domain characteristics of acoustic emission can reflect issues such as rock structure and stress conditions that are difficult to analyze in time domain parameters. Studying the influence of immersion time on the mechanical properties and acoustic emission frequency domain characteristics of muddy mineral rocks is of great significance for comprehensively analyzing rock changes under water-rock coupling conditions. In this study, uniaxial compression tests and acoustic emission tests were conducted on sandstones containing montmorillonite under dry, saturated, and different immersion time conditions, with a focus on analyzing the effect of immersion time on the dominant frequency of rock acoustic emission. The results indicated that immersion time had varying degrees of influence on compressive strength, the distribution characteristics of dominant acoustic emission frequencies, the frequency range of dominant frequencies, and precursor information of instability failure for sandstones. After initial saturation, the strength of the rock sample decreased from 53.52 MPa in the dry state to 49.51 MPa, and it stabilized after 30 days of immersion. Both dry and initially saturated rock samples exhibited three dominant frequency bands. After different immersion days, a dominant frequency band appeared between 95 kHz and 110 kHz. After 5 days of immersion, the dominant frequency band near 0 kHz gradually disappeared. After 60 days of immersion, the dominant frequency band between 35 kHz and 40 kHz gradually disappeared, and with increasing immersion time, the dominant frequency of the acoustic emission signals increased. During the loading process of dry rock samples, the dominant frequency of acoustic emission signals was mainly concentrated between 0 kHz and 310 kHz, while after saturation, the dominant frequencies were all below 180 kHz. The most significant feature before the rupture of dry rock samples was the frequent occurrence of high frequencies and sudden changes in dominant frequencies. Before rupture, the characteristics of precursor events for initially saturated and immersed samples for 5, 10, and 30 days were the appearance and rapid increase in sudden changes in dominant frequencies, as well as an enlargement of the frequency range of dominant frequencies. After 60 days of immersion, the precursor characteristics of rock sample rupture gradually disappeared, and sudden changes in dominant frequencies frequently occurred at various stages of sample loading, making it difficult to accurately predict the rupture of specimens based on these sudden changes.

Insight on molecular interactions in shrinkage of Na-montmorillonite clay by molecular dynamics simulation

Expansive soils are known to be hazardous materials for infrastructure due to their high shrinking or swelling potential. Understanding the shrinking factors of expansive soils such as montmorillonite (MMT) is essential for predicting their mechanical properties. The interactions between the components of Na-MMT clays, e.g., MMT layer–layer (LL), layer–cation (LC), layer–water (LW) and water–cation (WC), are responsible for its shrinking behavior. In this study, molecular dynamics simulation and grand canonical Monte Carlo simulations are used to investigate the interaction energy evolution in the layered structure of Na-MMT for the shrinkage mechanisms analysis of clay. The results of simulation indicate that the magnitude of the interaction energy contributed by the interlayer cations dehydration is the driving force of the interlayer shrinkage. Furthermore, in the hydrated state, with one water layer, two water layers and three water layers, the attractive interactions between WC and LW, maintain the stability of the clay layers. However, at the dry state, the interaction energy between layers and cations appears to be the most essential component in holding the stacked layers together, which provides structural stability to the clay sheets. Finally, the study reveals that intermolecular interactions contribute to the mechanical properties of clays such as cohesive and elastic properties.

Potential Predictability of Two-Year Droughts in the Missouri River Basin

Abstract Potential predictability of 2-yr droughts indicated by low runoff in the consecutive April–September seasons in the upper Missouri River basin (UMRB) and lower Missouri River basin (LMRB) is examined with observed estimates and climate models. The majority of annual runoff is generated in April–September, which is also the main precipitation and evapotranspiration season. Physical features related to low April–September runoff in both UMRB and LMRB include a dry land surface state indicated by low soil moisture, low snowpack indicated by low snow water equivalent, and a wave train across the Pacific–North American region that can be generated internally by the atmosphere or forced by the La Niña phase of El Niño–Southern Oscillation. When present in March, these features increase the risk of low runoff in the following April–September warm seasons. Antecedent low soil moisture significantly increases low runoff risks in each of the following two April–September, as the dry land surfaces decrease runoff efficiency. Initial low snow water equivalent, especially in the Missouri River headwaters of Montana, generates less runoff in the subsequent warm season. La Niña increases the risk of low runoff during the warm seasons by suppressing precipitation via dynamically induced atmospheric circulation anomalies. Model simulations that differ in their radiative forcing suggest that climate change increases the predictability of 2-yr droughts in the Missouri River basin related to La Niña. The relative risk of low runoff in the second April–September following a La Niña event in March is greater in the presence of stronger radiative forcing. Significance Statement Drought spanning consecutive years in the upper Missouri River basin (UMRB) and lower Missouri River basin (LMRB) poses threats to a region whose economy depends on reliable water quantity to support transportation and recreation, adequate water supply for irrigated agriculture, and sufficient streamflow to generate hydroelectric power. We examined physical features in March related to low runoff in the following April–September—low soil moisture, low snow water equivalent, and La Niña events—and examined their effect on the risk of 2-yr drought occurrences. These physical features lead to sustained impacts on the surface water balance. Low snow water equivalent generates less runoff, low soil moisture reduces the runoff efficiency of converting precipitation into runoff, and La Niña inhibits warm-season precipitation and runoff via atmospheric circulation anomalies.

Sweet corn phytoglycogen dendrimers as a lyoprotectant for dry‐state protein storage

AbstractProtein biotherapeutics typically require expensive cold‐chain storage to maintain their fold and function. Packaging proteins in the dry state via lyophilization can reduce these cold‐chain requirements. However, formulating proteins for lyophilization often requires extensive optimization of excipients that both maintain the protein folded state during freezing and drying (i.e., “cryoprotection” and “lyoprotection”), and form a cake to carry the dehydrated protein. Here we show that sweet corn phytoglycogens, which are glucose dendrimers, can act as both a protein lyoprotectant and a cake‐forming agent. Phytoglycogen (PG) dendrimers from 16 different maize sources (PG1‐16) were extracted via ethanol precipitation. PG size was generally consistent at ~70–100 nm for all variants, whereas the colloidal stability in water, protein contaminant level, and maximum density of cytocompatibility varied for PG1‐16. 10 mg/mL PG1, 2, 9, 13, 15, and 16 maintained the activity of various proteins, including green fluorescent protein, lysozyme, β‐galactosidase, and horseradish peroxidase, over a broad range of concentrations, through multiple rounds of lyophilization. PG13 was identified as the lead excipient candidate as it demonstrated narrow dispersity, colloidal stability in phosphate‐buffered saline, low protein contaminants, and cytocompatibility up to 10 mg/mL in NIH3T3 cell cultures. All dry protein‐PG13 mixtures had a cake‐like appearance and all frozen protein‐PG13 mixtures had a Tg' of ~ −26°C. The lyoprotection and cake‐forming properties of PG13 were density‐dependent, requiring a minimum density of 5 mg/mL for maximum activity. Collectively these data establish PG dendrimers as a new class of excipient to formulate proteins in the dry state.

Assessing spatiotemporal variation in dry-wet abrupt alternation using an improved process-based approach

Study regionThe Pearl River Basin (PRB), located in the south of China, has a tropical to subtropical climate. Study focusIn this study, we present an improved process-based approach to assess the intensity of the Dry-Wet Abrupt Alternation (DWAA) events, considering both the transition gap (alternation) and the transition rate (urgency) between dry and wet states. Using daily precipitation data from 1961 to 2020 across 75 meteorological stations in the PRB, we analyze the temporal and spatial evolution patterns of DWAA events. New hydrological insights for the regionThe findings reveal that: (1) DWAA events in the western region generally occur less frequently but with higher intensity. (2) Dry-to-wet (D-W) events have an urgency intensity of 1.35, almost twice that of wet-to-dry (W-D) events at 0.69. However, the alternation intensity of W-D is only slightly higher by 0.17 compared to D-W. (3) The alternation and urgency changes in D-W events are asynchronous, with alternation intensity initially decreasing from 9.7 to 9.27, then increasing to 9.58, while urgency decreases continuously from 1.66 to 1.07. (4) The alternation and urgency changes in W-D events are synchronous. The alternation intensity initially decreases from 9.7 to 9.06, then rises to 10.1, while the urgency intensity decreases from 0.68 to 0.58 before subsequently climbing to 0.8.

Synthesis of mannose conjugated biodegradable polyester-based nanocarriers and their binding study with Concanavalin A

Synthesis of mannose conjugated biodegradable polyester-based nanocarriers and their binding study with Concanavalin A

PH-responsive size- and charge-selective block copolymer membrane for the separation of small proteins

Blue-light-induced RAFT polymerization was utilized to synthesize poly(N,N-dimethylacrylamide)–block–polystyrene (PDMA–b–PS) diblock copolymers to obtain 40 g per batch for membrane fabrication. Larger isoporous membranes (≈ 0.5 m · 0.3 m) with pore diameters of ≈ 25 nm in the dry state and around 4 nm in the wet state were obtained by the combination of self-assembly and non-solvent induced phase separation (SNIPS). Membranes were post-modified with hydrochloric acid to impart negatively charged, pH-responsive poly(acrylic acid)–block–polystyrene (PAA–b–PS) membranes. Meanwhile all proteins like cytochrome C, insulin, lysozyme, myoglobin, and ovalbumin were fully rejected by the pristine PDMA–b–PS membrane, the PAA–b–PS membrane exhibited the rejection of proteins with a hydrodynamic radius Rh ≥ 1.9. A real selectivity of 4.1 for the positively charged protein cytochrome C compared to the similarly sized, but negatively charged insulin, as well as a real selectivity of 16.1 towards the negatively charged ovalbumin was obtained showing the size- and charge-selective characteristics of the PAA–b–PS membrane for protein separation.