Swelling Behavior Research Articles

Exploring Peculiar Properties of Graded Rubber

A styrene-butadiene rubber having a gradient crosslink density in the thickness direction was simply prepared by vulcanizing under a temperature gradient to study its mechanical properties and swelling behavior. The graded rubber exhibited considerable strain recovery after stress removal despite having a low crosslinked part. Notably, the graded rubber also manifested greater hysteresis loss during cyclic test compared to a homogeneously crosslinked rubber, even though they had similar initial moduli. Furthermore, anomalous swelling behavior was observed in the graded rubber. The graded rubber exhibited shape transformation upon swelling. The mechanism was thoroughly explained using gel swelling theory under constraints. This must be a common phenomenon in graded rubbers with a crosslink gradient in the thickness direction. This comprehensive research provides a novel approach for material design with tailored properties and promising applications for this potential material.

Design a variety of cation exchange hydrogel resins using gamma irradiation to remove hard/scale metal cations from saline water under different circumstances

This study aims to develop a series of cation exchange hydrogel resins via gamma irradiation technique through copolymerizing styrene sodium sulfonate with three acrylamide derivatives (designated as poly(X-co-styrene sodium sulfonate), where X refers to acrylamide (PAASS), methacrylamide (PMASS), and isopropyl acrylamide (PIASS)). The prepared hydrogel resins were characterized and tested for the adsorption removal of hard/scale metal cations (e.g., Ca2+, Mg2+, Ba2+, and Sr2+) from saline water under varying conditions. Results demonstrated that PMASS and PIASS displayed closed porous networks with a significant pH-responsive swelling behavior, increasing from 1.41 to 5.62 g/g in acidic conditions and approximately 41.49 to 45.83 g/g under neutral conditions swelling ratios, while PAASS exhibited an open porous network structure with the stable swelling ratio of around 35 g/g within mild and neutral pH ranges. All hydrogel resins also showed rapid initial adsorption of Ca2+ > Mg2+ > Ba2+ > Sr2+, depending on ionic metal size, with adsorption equilibrium within 3–6 h. Maximum removal was achieved at neutral-basic pH when sulfonate groups were fully deprotonated with a total capacity of about ~ 147–175 mg/g overall mixed metal ions. When exposed to lower concentration solutions, about 87% of metal ions were effectively removed.

A Layer-by-Layer Polycaprolactone/Chitosan-Based Biomimetic Hybrid Nanofibroporous Scaffold for Enhanced Skin Tissue Regeneration: Integrating Solution Blow Spinning and Freeze Casting Techniques.

Nanofibers, with their high surface area-to-volume ratio, elasticity, and mechanical strength, significantly enhance scaffold structures for skin tissue engineering. The present study introduces a unique method of combining solution blow spinning (SBS) and freeze casting to fabricate biomimetic hybrid nanofibroporous scaffolds (BHNS) using polycaprolactone (PCL) and chitosan (CH). The developed scaffolds mimic the fibrous porous natural extracellular matrix (ECM) architecture, promoting cell adhesion, proliferation, and matrix deposition. The combined SBS and freeze-casting processes resulted in scaffolds with high porosity and optimal mechanical strength, crucial for effective skin regeneration. Scanning electron microscopy (SEM) confirmed the uniform, nonwoven, and beadless architecture of the PCL fibers and the fibroporous nature of the PCL/CH scaffolds. The scaffolds exhibited excellent swelling behavior, controlled degradation rates, and enhanced mechanical properties. In vitro cell studies demonstrated scaffold cell-supportive properties in terms of cell attachment, proliferation, and migration. This innovative layer-by-layer fabrication technique, integrating nanofibers with freeze-cast scaffolds, represents a significant advancement in skin tissue engineering, promising improved outcomes in wound healing and regenerative medicine.

Rheological properties and 3D printability of SBS/CR-modified asphalt binder with C9 petroleum resin for crack filling

IntroductionThis study investigates rheological behavior and 3D printability of SBS-, CR-, SBS/CR-modified asphalt binder with C9 petroleum resin (C9PR) for crack filling.MethodsThirteen types of modified asphalt binders with respective C9PR of 0 wt%, 1 wt%, 2 wt%, 3 wt% were prepared and evaluated for their microstructure, physical properties, compatibility, rheological properties, and 3D printability.ResultsThe results show that SBS, CR, and C9PR influenced significantly on rheological properties and 3D printability of modified asphalt binders. Physical blending and improved storage stability of modified asphalt binders were observed with the addition of C9PR. In addition, the combination of SBS and CR showed enhanced viscoelastic behavior and temperature sensitivity compared to the base asphalt binder due to the increased swelling behavior of SBS and CR in asphalt binders by C9PR.DiscussionAsphalt binder with 3 wt% SBS, 15 wt% CR, and 1 wt% C9PR showed improved viscosity, elasticity, compatibility, high-temperature rutting resistance, and fatigue resistance. Additionally, C9PR expanded 3D printable temperature range of modified asphalt binder, leading to its potential use as an additive in 3D printed asphalt binders.

Microscopic swelling behaviors and structural responses of aggregate system: A coarse-grained molecular dynamics study

Microscopic swelling behaviors and structural responses of aggregate system: A coarse-grained molecular dynamics study

Development of hyaluronic acid/β-cyclodextrin semi-interpenetrating network hydrogels for prolonged delivery of water-soluble drug sunitinib malate.

Sunitinib malate (SUM), widely used in cancer treatment for its anti-VEGF properties, has also been explored for ocular neovascular diseases. For ocular applications, sustained drug release is essential to reduce dosing frequency. Hyaluronic acid (HA)-based hydrogels are commonly used for controlled drug delivery, but their hydrophilicity leads to rapid drug diffusion, especially for water-soluble drugs like SUM. To address this, β-cyclodextrin (β-CD) polymers (2-300 kDa) were incorporated into tyramine-conjugated HA (HA-TA) (200-400 kDa) networks to extend drug release via host-guest inclusion complexes. SUM-CD intermolecular interactions were identified and characterised by 1H NMR and FTIR spectroscopies, and NOESY spectra further confirmed a 2 SUM: 1 βCD inclusion complex. β-CD polymers (10 % w/v) were integrated into HA-TA (0.25, 0.5, 1 % w/v) networks crosslinked through enzymatic crosslinking using horseradish peroxidase and hydrogen peroxide, forming a semi-interpenetrating polymer network hydrogel. This hydrogel exhibited faster gelation, enhanced swelling behaviour, higher drug loading capacity, a denser matrix, and a longer SUM release duration compared to HA-TA hydrogels. In an in vitro flow model, post-gelation loading of SUM led to a longer release duration than pre-loading, with release continuing over 20 days. The HA-CD semi-IPN hydrogel therefore warrants further exploration for its potential ocular applications.

Preparation of Hydrogels of Methacrylamide with Mono and Dicarboxylic Acids: Investigation of Their Swelling Behavior

Methacrylamide (MAAm) hydrogels were synthesized with mono- (crotonic acid, CrA) and dicarboxylic (maleic acid, MAA) acids via radical copolymerization, utilizing potassium persulfate (KPS) as the initiator and methylenebisacrylamide (MBAAm) as the crosslinker. The swelling behavior of the resulting hydrogels was systematically investigated, with particular focus on the effects of monomer ratio, initiator and crosslinker concentrations, as well as polymerization temperature. These parameters were optimized to maximize the swelling ratio. For poly(MAAm/CrA) hydrogels, the formulation containing 85/15 MAAm/CrA (mol/mol), 2 mol% KPS, 1 mol% MBAAm, and synthesized at 55 °C exhibited the highest swelling capacity (480%) in distilled water. In contrast, for poly(MAAm/MAA) hydrogels, the composition of 75/25 MAAm/MAA (mol/mol) with 1 mol% KPS, 1 mol% MBAAm, and polymerized at 55 °C showed a maximum swelling of 1100%. Further investigations explored the influence of pH, temperature, and electrolyte concentration and type on the swelling properties of the hydrogels prepared under optimized conditions. Both hydrogels demonstrated peak swelling behavior at pH 7, with their swelling profiles varying in response to changes in temperature, electrolyte concentration, and electrolyte type. Swelling kinetics studies revealed that the MAAm/CrA hydrogel exhibited Fickian diffusion in distilled water at room temperature, while the MAAm/MAA hydrogel followed a non-Fickian diffusion mechanism. Scanning electron microscopy (SEM) analysis indicated that the hydrogels synthesized under optimal conditions possessed a porous and well-organized network structure.

Injectable, in-situ forming, tunable, biocompatible gelatin hydrogels for biomedical applications.

Gelatin hydrogels have drawn attention for their diverse biomedical applications due to their flexible physiochemical properties. However, such gelatin hydrogels are made of toxic crosslinkers and photoinitiators, restricting their non-invasive deep tissue application. The in-situ forming chemical crosslinked without such toxic crosslinker and UV light has not been explored under physiological conditions. This study establishes a simple method to fabricate an injectable click-chemistry-based in-situ forming gelatin hydrogel in a physiological environment (without toxic UV or photoinitiator) with tunable physiochemical properties to modulate cellular response. Using Divinyl Sulfone (DVS) modification, gelatin hydrogel (GelVS) is optimized with tunable degradation properties, moduli (100 Pa -1000 Pa), gelation time, swelling, degradation, and viscoelastic behaviour. The in-vitro results using fibroblast and stem cells show that the hydrogel and its precursors were cytocompatible with diverging feedback of cells as the modulus varies. The in-vivo analysis for injectability, degradation, and biocompatibility of the GelVS hydrogel displays their biocompatible nature and lasts up to 30 days at the injecting site. Overall results indicate that DVS-modified GelVS hydrogel will be a great system with tunable physicochemical properties to modulate favorable cellular response for tissue regeneration and non-invasive deep tissue application.

Gastro retentive floating drug delivery system of levofloxacin based on Aloe vera hydrogel: In vitro and in vivo assays

Gastro retentive drug delivery systems (GRDDS) have gained immense popularity as they reduce dosing frequency, improve bioavailability, and enhance patient compliance. Herein, a plant-based, controlled swelling, and pH-sensitive GRDDS based on Aloe vera hydrogel and cellulose was developed for the sustained release of levofloxacin (LEVO). The properties of five various floating tablet formulations including dynamic swelling, pH-responsiveness, hardness, friability, drug release, and buoyant time were evaluated. The optimized formulation (FF) was characterized using FTIR and SEM, and the surface morphology exhibited a porous texture with microchannels that facilitated tablet swelling and prolonged release of LEVO. The formulation FF remained buoyant (> 12 h) in the simulated gastric fluid with a buoyancy time of 303 s. A pH-dependent swelling behavior of the formulation FF was revealed with the highest swelling (7.1 g/g) in water, followed by buffers of pH 6.8 (5.4 g/g), 4.5 (3.8 g/g), and 1.2 (2 g/g). The controlled release of LEVO was demonstrated for >12 h following the Hixson-Crowell model and non-Fickian diffusion. Pharmacokinetic parameters of LEVO were determined using in vivo studies. The non-toxic nature of the formulation under study was demonstrated. The results render this approach promising in reducing the dosing frequency, suggesting its potential for clinical applications.

Unveiling Swelling and Erosion Dynamics: Early Development Screening of Mirabegron Extended Release Tablets

Although the development of extended release (ER) matrices has been extensively investigated, understanding the most appropriate mechanism of drug release to achieve the desired release remains a cost- and time-consuming challenge in the early stages of formulation development. This study aimed to investigate the early stage of developing ER hydrophilic matrix tablets containing mirabegron as a model drug, focusing on the effects of polymer type, diluent type, and polymer amount on critical quality attributes (CQAs), namely, tablet swelling and erosion behavior. A full factorial design was employed to explore the interactions of control factors through multivariate regression analysis, emphasizing the application of quality by design (QbD) principles. The swelling and erosion performances of 72 formulations were evaluated. The swelling data were fitted to the Vergnaud model. Finally, in vitro drug release profiles were investigated for four of the formulations studied. The polymer type, diluent type, and polymer amount had distinct effects on the swelling and erosion behavior of the ER matrix tablets. Compared with those with isomalt (G720) or dextrate (DXT), formulations with polyethylene glycol 8000 (P8000) consistently exhibited greater swelling. Additionally, higher molecular weight was correlated with increased swelling within the same polymer type. Hydroxypropylmethylcellulose (HPMC) and polyethylene oxide (PEO)-based formulations showed higher swelling rates, while polyvinyl alcohol (PVA-80) displayed the highest erosion percentage. The findings highlight the significance of incorporating early-stage screening designs to maximize efficiency and optimize time and resource. This approach enables the development of a comprehensive understanding of drug release mechanisms from ER matrix tablets.Graphical abstract

Optimization of swelling and mechanical behavior of novel pH-sensitive terpolymer biocomposite hydrogel based on activated carbon for removal brilliant blue dye from aqueous solution

Optimization of swelling and mechanical behavior of novel pH-sensitive terpolymer biocomposite hydrogel based on activated carbon for removal brilliant blue dye from aqueous solution

Crosslinking by Click Chemistry of Hyaluronan Graft Copolymers Involving Resorcinol-Based Cinnamate Derivatives Leading to Gel-like Materials.

The well-known "click chemistry" reaction copper(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) was used to transform under very mild conditions hyaluronan-based graft copolymers HA(270)-FA-Pg into the crosslinked derivatives HA(270)-FA-TEGERA-CL and HA(270)-FA-HEGERA-CL. In particular, medium molecular weight (i.e., 270 kDa) hyaluronic acid (HA) grafted at various extents (i.e., 10, 20, and 40%) with fluorogenic ferulic acid (FA) residue bonding propargyl groups were used in the CuAAC reaction with novel azido-terminated crosslinking agents Tri(Ethylene Glycol) Ethyl Resorcinol Acrylate (TEGERA) and Hexa(Ethylene Glycol) Ethyl Resorcinol Acrylate (HEGERA). The resulting HA(270)-FA-TEGERA-CL and HA(270)-FA-HEGERA-CL materials were characterized from the point of view of their structure by performing NMR studies. Moreover, the swelling behavior and rheological features were assessed employing TGA and DSC analysis to evaluate the potential gel-like properties of the resulting crosslinked materials. Despite the 3D crosslinked structure, HA(270)-FA-TEGERA-CL and HA(270)-FA-HEGERA-CL frameworks showed adequate swelling performance, the required shear thinning behavior, and coefficient of friction values close to those of the main commercial HA solutions used as viscosupplements (i.e., 0.20 at 10 mm/s). Furthermore, the presence of a crosslinked structure guaranteed a longer residence time. Indeed, HA(270)-FA-TEGERA-CL-40 and HA(270)-FA-HEGERA-CL-40 after 48 h showed a four times greater enzymatic resistance than the commercial viscosupplements. Based on the promising obtained results, the crosslinked materials are proposed for their potential applicability as novel viscosupplements.

Efficacy of 3D-printed chitosan‑cerium oxide dressings coated with vancomycin-loaded alginate for chronic wounds management

Multifunctional wound dressings with antibacterial and antioxidant properties hold significant promise for treating chronic wounds; however, achieving a balance of these characteristics while maintaining biocompatibility is challenging. To enhance this balance, this study focuses on the design and development of 3D-printed chitosan-matrix composite scaffolds, which are incorporated with varying amounts of cerium oxide nanoparticles (0, 1, 3, 5, and 7 wt%) and subsequently coated with a vancomycin-loaded alginate layer. The structure, antibiotic drug delivery kinetics, biodegradation, swelling, biocompatibility, antibacterial, antioxidant, and cell migration behaviors of the fabricated dressings were evaluated in-vitro. The findings reveal that all of the formulations demonstrated a robust antibacterial effect against S. aureus bacterial strains in disk diffusion tests. Furthermore, the dressings containing cerium oxide nanoparticles exhibited proper antioxidant capabilities, with over 78.1 % reactive oxygen species (ROS) scavenging efficiency achieved with 7 % cerium oxide nanoparticles. The sample containing 5 % cerium oxide nanoparticles was identified as the optimal formulation, characterized by the most favorable cell biocompatibility, an ROS scavenging ability of over 73.4 %, and the potential to close the wound bed within 24 h. This study highlights that these dressings are promising for managing chronic wounds by preventing infection and oxidative stress in a correct therapeutic sequence.

A Finite-Element-Based Investigation of the Influence of the Production Environment on Fuel Cell Membrane Electrode Assemblies During Manufacturing

The manufacturing process for membrane electrode assemblies (MEAs), from coating to stack assembly, is typically performed under climate-controlled conditions due to the hygroscopic properties of catalyst-coated membranes (CCMs). Large climate-controlled areas in the assembly line not only increase the energy consumption but also limit the scalability of the production line. In this study, experiments were conducted to analyze the effects of ambient humidity on the mechanical properties of a CCM. The hygroscopic swelling behavior of a commercial CCM with an ePTFE-reinforced membrane was also characterized. Using the finite element method, a 3D numerical model covering the entire MEA assembly process was developed, allowing for a numerical investigation of different climate control strategies. The influence of ambient humidity on the dimensional changes in the CCM, which leads to significant stress on the CCM due to mechanical constraints and thus to deformation of the MEA product, was simulated and validated experimentally using optical measurements. Finally, the critical steps during MEA assembly were identified, and a recommendation for the optimal humidity range for climate control was derived.

Robust and low swelling polyacrylamide/sodium alginate dual-network hydrogels via multiple freezing strategy toward amphibious motion sensors

The swelling and disintegration behavior of conventional hydrogels in liquid environments significantly affects their mechanical and ionic conductive properties, thereby limiting their widespread application in underwater setting. Herein, we propose a multiple freezing (MF) strategy for the construction of polyacrylamide/sodium alginate (PAM/SA) dual-network hydrogels that exhibit excellent anti-swelling properties and high toughness. The MF strategy employs a combination of freeze casting and refreezing to promote a cascading enhancement of polymer network density, resulting in a highly dense polymer network. This dense network structure endows the hydrogel with impressive tensile strength (3.491 MPa), exceptional elongation at break (435.71 %), and high toughness (5.291 MJ m⁻3), along with remarkable ionic conductivity (142.75 mS m⁻1) and sensitivity (GF = 2.278). These properties enable the hydrogel to function as a flexible sensor capable of detecting various human movement patterns. Its excellent resistance to swelling makes it an ideal material for underwater sensors, effectively monitoring different swimming strokes. This strategy provides a straightforward and effective means to enhance the mechanical strength and adaptability of traditional hydrogels in aquatic environments, demonstrating significant potential for applications in underwater sensing.

Mechanism analysis of effect of MgO on reduction swelling behaviour of iron pellets in CO/H2 atmosphere based on first-principles calculations

Mechanism analysis of effect of MgO on reduction swelling behaviour of iron pellets in CO/H2 atmosphere based on first-principles calculations

Swelling Behavior of Acrylate-Based Photoresist Polymers Containing Cycloaliphatic Groups of Various Sizes.

Photoresist polymers containing cycloaliphatic acrylic monomers have been synthesized for use in the microcircuits of semiconductors. Although cycloaliphatic acrylic monomers exhibit a high etch resistance and excellent thermal properties, their large size increases the distance between the main chains of the resulting polymers. This increased distance facilitates the penetration of a developer between the main chains, which leads to swelling and thus pattern collapse, distortion, and delamination, thereby complicating the fabrication of microcircuits. To solve this problem, various large developers were used in previous studies to reduce the swelling effect. However, these developers could not easily dissolve the unexposed regions of the resist. To overcome this issue, we designed photoresist polymers with smaller functional groups to decrease the degree of swelling. Specifically, ArF photoresist polymers were synthesized from monomers with various sizes of functional groups. We confirmed that the polymer synthesized using cyclohexyl methacrylate (CHMA), which had the smallest functional group, exhibited the shortest distance between the main chains. Consequently, this polymer showed the least swelling, with a swelling ratio of 109%. In contrast, the polymers synthesized using isobornyl acrylate (IBOA) and dicyclopentanyl methacrylate (TCDMA), which have large functional groups, exhibited greater distances between the main chains, resulting in swelling ratios of 114% and 112%, respectively. The polymer with a swelling ratio of 109% showed excellent patterning properties, while those with swelling ratios of 114% and 112% were delaminated by the developer. Our work introduces a novel approach to help reduce the swelling effect and achieve high-quality patterns in negative photoresists.

A functional dual responsive CMC/OHA/SA/TOB hydrogel as wound dressing to enhance wound healing.

Within the clinical realm, the complexities of wound healing have consistently presented formidable challenges. Recent advancements, notably in hydrogel technologies, have broadened the therapeutic spectrum. This study focuses on investigating a novel dual responsive composite hydrogel for wound healing. This hydrogel is ingeniously designed to maintain an optimal moist environment, expedite healing, and combat bacterial infection during wound recovery. This study combining carboxymethyl chitosan (CMC), oxidized hyaluronic acid (OHA), and sodium alginate (SA), in addition, tobramycin (TOB) was incorporated to create a CMC/OHA/SA/TOB hydrogel. Hydrogel cross-linking was verified by infrared spectroscopy, and the microstructure was examined with scanning electron microscopy. We explored its swelling and degradation behaviors in different pH environments. The drug release profile and biocompatibility was evaluated via cytotoxicity and hemolysis assays. The antibacterial efficacy of hydrogel was tested in both solid and liquid media. Additionally, the wound models in Sprague-Dawley (SD) rat was employed to investigate the hydrogel's wound healing capabilities in vivo. Results showed that CMCOHA/SA/TOB hydrogel was effectively cross-linked with a network structure. The hydrogel exhibited pronounced responsiveness in its swelling and degradation characteristics, which was significantly influenced by different levels of pH. In vitro results demonstrated that the CMC/OHA/SA/TOB hydrogel exhibits limited cytotoxicity and hemolysis, coupled with a drug release profile of dual responsive characteristics. Antibacterial activity of the hydrogel against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was confirmed. Furthermore, in vivo experiments underscored the hydrogel's proficiency in promoting wound healing, highlighting its potential for clinical applications. The CMC/OHA/SA/TOB hydrogel not only fosters a moist environment essential for wound healing and enhances structural stability, but it also exhibits functional dual responsive capabilities in swelling and degradation. These distinctive abilities enable the precise release of TOB, thereby optimizing wound healing.

HRMAS NMR for Studying Solvent-Induced Mobility of Polymer Chains and Metallocene Migration Into Low-Density Polyethylene (LDPE).

HRMAS (high-resolution magic angle spinning) nuclear magnetic resonance (NMR) spectroscopy of low-density polyethylene (LDPE) affords 1H and 13C NMR spectra with superior resolution. For acquiring HRMAS NMR spectra, the polymer is first swollen with representative organic solvents. Then, the samples are measured with a conventional solid-state NMR spectrometer in the wideline mode or at the low spinning speed of 2 kHz. Anisotropic interactions like CSA (chemical shift anisotropy) and dipolar interactions are reduced due to the additional mobility of the polymer chains in the presence of the solvent within the polymer network. The combined effect of this mobility and MAS leads to signals with substantially reduced halfwidths as compared to classic MAS of the dry polymer. With HRMAS, all signals of the polymer become visible, and the spectra can be used for a quick and easy assessment of the polymer swelling behavior in diverse solvents. Being able to characterize polymers on the molecular level, and identifying the solvents that penetrate the polymer network best, enables the study of post-synthesis modifications of the polymers. It is demonstrated by paramagnetic HRMAS that the metallocene nickelocene (Cp2Ni) penetrates the LDPE network along with the solvent and is homogeneously dispersed in the polymer. SEM images prove that the structure of the polymer is not altered by the presence of a solvent and Cp2Ni. The impact of the paramagnetic Cp2Ni on the 1H signal halfwidth and T1 time of LDPE is studied. HRMAS allows a quick assessment of metal complexes regarding their ability to penetrate the LDPE network and therefore supports future studies of catalytic polymer degradation.

Charge State of Weak Polyelectrolyte Brushes Determines Salt-Dependent Swelling and Hysteretic Behavior.

We investigate the combined effects of ionizable monomer fraction f, pH, and monovalent salt concentration Cs on the swelling of weak polyelectrolyte brushes (PEBs) by using in situ ellipsometry. Our system consists of random copolymers of basic (2-(dimethylamino)ethyl acrylate, DMAEA) and neutral (2-hydroxyethyl acrylate, HEA) monomers at varying fractions of ionizable monomer. Swelling of the brushes qualitatively follows the trends predicted by scaling laws for PEBs under different charge states but quantitatively deviates at specific ionic strengths and pH values. We posit these deviations stem from the lack of excluded volume effects and assumptions of strong chain stretching in current theoretical models. Most notably, we uncover a salt-dependent, nonmonotonic hysteretic behavior as weak PEB brushes are cycled from protonated to deprotonated and back. The nonmonotonic trend of hysteresis with salt can be explained by an interplay between the protonation facilitating effects of salt in the osmotic regime and the charge screening effects in the salted regime, which make charge distribution along weak PEBs more uniform. Our results provide insight into the mechanisms that determine whether polyelectrolytes exhibit weak versus strong polyelectrolyte behavior in various environmental conditions.