Pub Date : 2026-03-07DOI: 10.1021/acs.macromol.5c03639
Vishnu L. Dharmaraj, Yun Fang, Matthew V. Tirrell
Polyelectrolyte complex micelles (PCMs) are nanoparticles that form through the associative phase separation between hydrophilic neutral–charged block copolymers and oppositely charged polyelectrolytes, resulting in a dense, charged core surrounded by a stabilizing neutral corona. Among other applications, these constructs have been studied as nonviral vectors for therapeutic nucleic acid delivery for a variety of potential clinical indications. Although prior research has focused on tailoring PCM morphology and size by modifying block polyelectrolyte characteristics, thermodynamic considerations have received comparatively little attention in the design of PCMs. In this study, we explore the dependencies of PCM complexation thermodynamics, particularly the entropy of complexation, on polyelectrolyte block length and PCM structure. We employ scattering (DLS, SAXS, MALS) to characterize PCM structure, while using isothermal titration calorimetry to provide quantitative thermodynamic data. Compared to complexation between homopolymers, we observe that PCM formation involving block polyelectrolytes introduces an entropic cost related to the neutral corona-forming block. This penalty depends on the sizes of the charged blocks but is relatively insensitive to the neutral block size. Scattering results show that PCM complexation entropy is not correlated with indicators of corona chain conformation, such as brush height and corona surface chain density. Rather, for PCMs composed of polymers with equal charged block lengths, complexation entropy is correlated with monomer density within the core and corona. Our findings also suggest a negligible free polymer concentration in PCM formulations with net neutral charge. These insights advance the rational design of block copolymers for encapsulating a wide array of therapeutically relevant cargos and deepen our understanding of the factors governing PCM formation.
{"title":"Effect of Polymer Structure on the Thermodynamics of Polyelectrolyte Complex Micelle Formation","authors":"Vishnu L. Dharmaraj, Yun Fang, Matthew V. Tirrell","doi":"10.1021/acs.macromol.5c03639","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03639","url":null,"abstract":"Polyelectrolyte complex micelles (PCMs) are nanoparticles that form through the associative phase separation between hydrophilic neutral–charged block copolymers and oppositely charged polyelectrolytes, resulting in a dense, charged core surrounded by a stabilizing neutral corona. Among other applications, these constructs have been studied as nonviral vectors for therapeutic nucleic acid delivery for a variety of potential clinical indications. Although prior research has focused on tailoring PCM morphology and size by modifying block polyelectrolyte characteristics, thermodynamic considerations have received comparatively little attention in the design of PCMs. In this study, we explore the dependencies of PCM complexation thermodynamics, particularly the entropy of complexation, on polyelectrolyte block length and PCM structure. We employ scattering (DLS, SAXS, MALS) to characterize PCM structure, while using isothermal titration calorimetry to provide quantitative thermodynamic data. Compared to complexation between homopolymers, we observe that PCM formation involving block polyelectrolytes introduces an entropic cost related to the neutral corona-forming block. This penalty depends on the sizes of the charged blocks but is relatively insensitive to the neutral block size. Scattering results show that PCM complexation entropy is not correlated with indicators of corona chain conformation, such as brush height and corona surface chain density. Rather, for PCMs composed of polymers with equal charged block lengths, complexation entropy is correlated with monomer density within the core and corona. Our findings also suggest a negligible free polymer concentration in PCM formulations with net neutral charge. These insights advance the rational design of block copolymers for encapsulating a wide array of therapeutically relevant cargos and deepen our understanding of the factors governing PCM formation.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"50 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147368061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-07DOI: 10.1021/acs.macromol.5c03323
M. Ali Aboudzadeh, Leire Sangroniz, Olivier Coulembier, Marcello Ferranti, Salvatore Costanzo, Nino Grizzuti, D. Cavallo, Alejandro J. Müller
In polymer crystals, chains are closely packed within unit cells. If they are heated above their melting point, they require a specific temperature and time to revert their ordered conformations to isotropic random coils in the melt. When the temperature is slightly above the melting point and all crystals have melted, the chains may retain a memory of the conformations they had in the crystals, i.e., they remember some of the extended or oriented conformations that they had in crystallographic registry. This causes enhanced recrystallization, a property denoted melt memory. Its exact nature remains a central question in polymer crystallization. Here, we combine small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) self-nucleation experiments to systematically investigate the molecular origin of melt memory in poly(ε-caprolactone) (PCL) and poly(ethylene oxide) (PEO) model samples, spanning a range of molecular weights from oligomers to highly entangled polymers. The entanglement molecular weights (Me) were experimentally determined with rheological techniques using a large number of samples. To quantify intermolecular interactions and rheological constraints, we introduce a dimensionless interaction index that accounts for crystallinity-weighted intermolecular interactions and chain packing in the melt. This index rises sharply in oligomeric samples and attains a maximum near Me. Without strong enough intermolecular interactions, melt memory cannot develop; for example, linear polyethylene does not exhibit melt memory. Conversely, in polar homopolymers, there is a critical chain length below which the intermolecular interaction density is not enough for memory to develop. Beyond this minimum chain length, melt memory is observed in polar homopolymers even in the absence of entanglements, in which case it is exclusively due to intermolecular interactions. Beyond Me, the melt memory increases as entanglements preserve the melt’s complexity, characterized by intermolecular interactions. These results establish a unified structure–property framework that links molecular weight, morphology, and intermolecular interactions to the melt memory of semicrystalline polar homopolymers.
{"title":"Decoupling the Roles of Chain Length, Entanglements, and Intermolecular Interactions on the Melt Memory of Semicrystalline Polar Homopolymers","authors":"M. Ali Aboudzadeh, Leire Sangroniz, Olivier Coulembier, Marcello Ferranti, Salvatore Costanzo, Nino Grizzuti, D. Cavallo, Alejandro J. Müller","doi":"10.1021/acs.macromol.5c03323","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03323","url":null,"abstract":"In polymer crystals, chains are closely packed within unit cells. If they are heated above their melting point, they require a specific temperature and time to revert their ordered conformations to isotropic random coils in the melt. When the temperature is slightly above the melting point and all crystals have melted, the chains may retain a memory of the conformations they had in the crystals, i.e., they remember some of the extended or oriented conformations that they had in crystallographic registry. This causes enhanced recrystallization, a property denoted melt memory. Its exact nature remains a central question in polymer crystallization. Here, we combine small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) self-nucleation experiments to systematically investigate the molecular origin of melt memory in poly(ε-caprolactone) (PCL) and poly(ethylene oxide) (PEO) model samples, spanning a range of molecular weights from oligomers to highly entangled polymers. The entanglement molecular weights (<i>M</i><sub>e</sub>) were experimentally determined with rheological techniques using a large number of samples. To quantify intermolecular interactions and rheological constraints, we introduce a dimensionless interaction index that accounts for crystallinity-weighted intermolecular interactions and chain packing in the melt. This index rises sharply in oligomeric samples and attains a maximum near <i>M</i><sub>e</sub>. Without strong enough intermolecular interactions, melt memory cannot develop; for example, linear polyethylene does not exhibit melt memory. Conversely, in polar homopolymers, there is a critical chain length below which the intermolecular interaction density is not enough for memory to develop. Beyond this minimum chain length, melt memory is observed in polar homopolymers even in the absence of entanglements, in which case it is exclusively due to intermolecular interactions. Beyond <i>M</i><sub>e</sub>, the melt memory increases as entanglements preserve the melt’s complexity, characterized by intermolecular interactions. These results establish a unified structure–property framework that links molecular weight, morphology, and intermolecular interactions to the melt memory of semicrystalline polar homopolymers.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"5 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147371528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-06DOI: 10.1021/acs.macromol.5c02892
Chenhao Hua, Weijie Yuan, Zhen Zhang, Jianyang Wang, Jin Huang
The regulation of the light absorption properties of organic photothermal drive materials needs to be achieved through extremely complex molecular structure engineering. This study proposes a newly solvent-directed coassembly strategy to achieve morphological control of conjugated oligomer nanostructures for fabrication of dual-band photothermal actuators. By coassembling the newly synthesized conjugated oligomer PDBTF with amphiphilic block copolymer PS-b-PAA, the transformation from spherical assemblies to needle-like rod-shaped nanoassemblies can be achieved by fine-tuning the ratio of the mixed solvent THF/MeOH. As the molecular packing order within the nanoassemblies was effectively modulated, the obtained nanostructures exhibit unique morphology-dependent optical absorption properties in the visible light band. Notably, these nanoassemblies were integrated into silicone rubber matrices, enabling mutiwavelength actuation. Under alternating 520/630 nm laser irradiation, the composite actuator achieves programmable rolling locomotion driven by asymmetric photothermal expansion. The nanoscale morphological controlling strategy based on solvent-modulated conjugated molecule supramolecular assembly opens avenues for advanced soft robotics manufacturing materials.
{"title":"Solvent-Directed Morphogenesis of Conjugated Oligomer Supramolecular Assemblies Enabling Dual-Wavelength Photothermally Actuated Smart Devices","authors":"Chenhao Hua, Weijie Yuan, Zhen Zhang, Jianyang Wang, Jin Huang","doi":"10.1021/acs.macromol.5c02892","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c02892","url":null,"abstract":"The regulation of the light absorption properties of organic photothermal drive materials needs to be achieved through extremely complex molecular structure engineering. This study proposes a newly solvent-directed coassembly strategy to achieve morphological control of conjugated oligomer nanostructures for fabrication of dual-band photothermal actuators. By coassembling the newly synthesized conjugated oligomer PDBTF with amphiphilic block copolymer PS-<i>b</i>-PAA, the transformation from spherical assemblies to needle-like rod-shaped nanoassemblies can be achieved by fine-tuning the ratio of the mixed solvent THF/MeOH. As the molecular packing order within the nanoassemblies was effectively modulated, the obtained nanostructures exhibit unique morphology-dependent optical absorption properties in the visible light band. Notably, these nanoassemblies were integrated into silicone rubber matrices, enabling mutiwavelength actuation. Under alternating 520/630 nm laser irradiation, the composite actuator achieves programmable rolling locomotion driven by asymmetric photothermal expansion. The nanoscale morphological controlling strategy based on solvent-modulated conjugated molecule supramolecular assembly opens avenues for advanced soft robotics manufacturing materials.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"26 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Supramolecular polymeric networks derive adaptability, processability, and toughness from reversible cross-links whose association and dissociation govern their macroscopic mechanics. Yet for many high-affinity linkers, their kinetic lability with high dissociation rate (kd > 1 s–1) restricts load bearing and network strength. Here we present a molecular-engineering strategy to kinetically stabilize supramolecular cross-links using a cucurbit[8]uril (CB[8]) host–guest platform. By extending the guest’s aromatic backbone to enhance intracavity π–π stacking and suppress axial slippage, we reduced the dissociation rate constant by over 100-fold to 10–2 s–1. When incorporated into polymeric networks, these persistent linkages produce strong yet adaptive hydrogels, whose viscoelastic relaxation directly reflects the molecular dissociation kinetics. Their high solubility further enables dense cross-linking, yielding tensile strengths up to 2 MPa and compressive strengths above 40 MPa. This work establishes molecular engineering of cross-link kinetics, demonstrated through the CB[8] model system, as a general and effective strategy for building high-performance supramolecular polymeric materials.
{"title":"Molecular Engineering of Persistent Supramolecular Cross-Links for Strong Polymeric Networks","authors":"Zhiqiang Zhou, Tianyi Yang, Haoran Lu, Hao Tang, Guanglu Wu, Hao Chen","doi":"10.1021/acs.macromol.6c00120","DOIUrl":"https://doi.org/10.1021/acs.macromol.6c00120","url":null,"abstract":"Supramolecular polymeric networks derive adaptability, processability, and toughness from reversible cross-links whose association and dissociation govern their macroscopic mechanics. Yet for many high-affinity linkers, their kinetic lability with high dissociation rate (<i>k</i><sub>d</sub> > 1 s<sup>–1</sup>) restricts load bearing and network strength. Here we present a molecular-engineering strategy to kinetically stabilize supramolecular cross-links using a cucurbit[8]uril (CB[8]) host–guest platform. By extending the guest’s aromatic backbone to enhance intracavity π–π stacking and suppress axial slippage, we reduced the dissociation rate constant by over 100-fold to 10<sup>–2</sup> s<sup>–1</sup>. When incorporated into polymeric networks, these persistent linkages produce strong yet adaptive hydrogels, whose viscoelastic relaxation directly reflects the molecular dissociation kinetics. Their high solubility further enables dense cross-linking, yielding tensile strengths up to 2 MPa and compressive strengths above 40 MPa. This work establishes molecular engineering of cross-link kinetics, demonstrated through the CB[8] model system, as a general and effective strategy for building high-performance supramolecular polymeric materials.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"29 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The adhesive properties of epoxy resins often deteriorate under combined exposure to moisture and heat, a phenomenon known as hygrothermal aging, which remains poorly understood due to the buried nature of adhesive interfaces. Since water molecules contribute to hygrothermal aging through both physical and chemical effects, understanding their distribution near the interface is an essential first step. To do so, we used back-incidence neutron reflectivity, a technique highly sensitive to buried interfaces and applicable to thick epoxy resins. Herein, we report the distribution of water in epoxy resin near the solid interface as a function of hygrothermal aging time and its correlation with interfacial adhesive properties. To address the effect of adherend surface chemistry on water distribution and adhesion, hydrogen-terminated silicon (SiH) and hydroxyl-terminated silicon (SiOH) substrates were used as model adherends. While the amount of water sorbed near the SiH interface remained almost unchanged during hygrothermal aging, that near the SiOH interface increased with aging time. Correspondingly, a marked reduction in adhesive energy was observed at the SiOH interface but not at the SiH interface. Such changes induced by hygrothermal aging at the SiOH interface could be associated with degradation reactions, leading to chain scission. This integrated approach provides molecular-level insights into the mechanisms of hygrothermal aging at buried interfaces, offering a general framework for correlating interfacial water behavior with adhesive degradation. The findings are expected to have far-reaching implications, not only for next-generation electronic devices, where epoxy resins are used as encapsulation materials, but also for mobility applications, such as automobiles and aircraft, as well as for infrastructure systems, where epoxy serves as a structural adhesive.
{"title":"Hygrothermal Aging Behavior of Epoxy Resin at Adhesive Interfaces","authors":"Ko Yamaguchi, Daisuke Kawaguchi, Atsuomi Shundo, Satoru Yamamoto, Masayasu Totani, Tatsuki Abe, Yuma Morimitsu, Noboru Miyata, Tsukasa Miyazaki, Yuwei Liu, Hiroyuki Aoki, Keiji Tanaka","doi":"10.1021/acs.macromol.5c02970","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c02970","url":null,"abstract":"The adhesive properties of epoxy resins often deteriorate under combined exposure to moisture and heat, a phenomenon known as hygrothermal aging, which remains poorly understood due to the buried nature of adhesive interfaces. Since water molecules contribute to hygrothermal aging through both physical and chemical effects, understanding their distribution near the interface is an essential first step. To do so, we used back-incidence neutron reflectivity, a technique highly sensitive to buried interfaces and applicable to thick epoxy resins. Herein, we report the distribution of water in epoxy resin near the solid interface as a function of hygrothermal aging time and its correlation with interfacial adhesive properties. To address the effect of adherend surface chemistry on water distribution and adhesion, hydrogen-terminated silicon (SiH) and hydroxyl-terminated silicon (SiOH) substrates were used as model adherends. While the amount of water sorbed near the SiH interface remained almost unchanged during hygrothermal aging, that near the SiOH interface increased with aging time. Correspondingly, a marked reduction in adhesive energy was observed at the SiOH interface but not at the SiH interface. Such changes induced by hygrothermal aging at the SiOH interface could be associated with degradation reactions, leading to chain scission. This integrated approach provides molecular-level insights into the mechanisms of hygrothermal aging at buried interfaces, offering a general framework for correlating interfacial water behavior with adhesive degradation. The findings are expected to have far-reaching implications, not only for next-generation electronic devices, where epoxy resins are used as encapsulation materials, but also for mobility applications, such as automobiles and aircraft, as well as for infrastructure systems, where epoxy serves as a structural adhesive.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"51 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Polyelectrolyte brushes are promising materials for achieving superlubricity, but conventional approaches requiring chemical surface grafting limit their broad applicability. Here, we demonstrate a simple, yet effective and readily scalable friction-control strategy using spherical polyelectrolyte brushes as lubricant additives. By tuning particle concentration, we precisely control the degree of polymer chain interpenetration, a key factor determining lubrication performance. Combining scattering, viscosity, and friction measurements, we identify three distinct lubrication regimes defined by brush interpenetration. Enhanced lubrication occurs at the concentration threshold separating the semidilute partly interpenetrated regime from the semidilute fully interpenetrated regime, which aligns closely with the transition between mixed and hydrodynamic lubrication. Our results point to a direct correlation between nanoscale structural transitions and macroscale friction behavior, offering a predictive framework for enhanced lubrication in diverse industrial applications.
{"title":"Friction Control via Tunable Interpenetration of Spherical Polyelectrolyte Brushes","authors":"Xin Liu, Shulei Yu, Yuhua Zhang, Ziyu Zhang, Li Li, Antonios Kelarakis, Bingge Feng, Jiusheng Li, Matthias Ballauff, Qi Liao, Xuhong Guo","doi":"10.1021/acs.macromol.5c03318","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03318","url":null,"abstract":"Polyelectrolyte brushes are promising materials for achieving superlubricity, but conventional approaches requiring chemical surface grafting limit their broad applicability. Here, we demonstrate a simple, yet effective and readily scalable friction-control strategy using spherical polyelectrolyte brushes as lubricant additives. By tuning particle concentration, we precisely control the degree of polymer chain interpenetration, a key factor determining lubrication performance. Combining scattering, viscosity, and friction measurements, we identify three distinct lubrication regimes defined by brush interpenetration. Enhanced lubrication occurs at the concentration threshold separating the semidilute partly interpenetrated regime from the semidilute fully interpenetrated regime, which aligns closely with the transition between mixed and hydrodynamic lubrication. Our results point to a direct correlation between nanoscale structural transitions and macroscale friction behavior, offering a predictive framework for enhanced lubrication in diverse industrial applications.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"15 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147368063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-06DOI: 10.1021/acs.macromol.5c03489
Mo Zhu, Lunliang Chen, Wendi Liang, Xin Guan, Lianwei Li
The adsorption behavior of hyperbranched polymers in liquid chromatography under critical conditions (LCCC) remains a fundamental puzzle due to their complex nonlinear architecture and the absence of a theoretical framework. Here, we overcome this challenge by synthesizing a series of hyperbranched polystyrene (HB-PS) with controlled branching densities (ρ = 1/35–1/400) and using functionalized linear PS references to eliminate chemical interference. Our study unveils a distinct topological paradigm: HB-PS exhibits a nonuniversal exclusion-to-adsorption transition, and the elution behavior strongly depends on the branching density under LCCC, in sharp contrast to the unified coelution point (CEP) behavior of linear and cyclic chains. This behavior originates from the high fractal dimension of hyperbranched structures, which amplifies intrachain excluded volume effects and significantly raises the conformational energy barrier during the exclusion-to-adsorption transition. Consequently, the conventional scaling relationship between the adsorption free energy and molecular weight breaks down. For near-incompressible hyperbranched polymers, elution becomes governed solely by size exclusion, and the CEP and critical adsorption behavior cease to exist. This work fundamentally revises the understanding of polymer adsorption under critical conditions and provides a new framework for analyzing complex topological polymers, with implications for highly branched biological macromolecules such as starch and glycogen.
{"title":"Exclusion-to-Adsorption Transition of Hyperbranched Polymers in Liquid Chromatography: Governed by Configurational Diversity and High Fractal Dimension","authors":"Mo Zhu, Lunliang Chen, Wendi Liang, Xin Guan, Lianwei Li","doi":"10.1021/acs.macromol.5c03489","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03489","url":null,"abstract":"The adsorption behavior of hyperbranched polymers in liquid chromatography under critical conditions (LCCC) remains a fundamental puzzle due to their complex nonlinear architecture and the absence of a theoretical framework. Here, we overcome this challenge by synthesizing a series of hyperbranched polystyrene (HB-PS) with controlled branching densities (ρ = 1/35–1/400) and using functionalized linear PS references to eliminate chemical interference. Our study unveils a distinct topological paradigm: HB-PS exhibits a nonuniversal exclusion-to-adsorption transition, and the elution behavior strongly depends on the branching density under LCCC, in sharp contrast to the unified coelution point (CEP) behavior of linear and cyclic chains. This behavior originates from the high fractal dimension of hyperbranched structures, which amplifies intrachain excluded volume effects and significantly raises the conformational energy barrier during the exclusion-to-adsorption transition. Consequently, the conventional scaling relationship between the adsorption free energy and molecular weight breaks down. For near-incompressible hyperbranched polymers, elution becomes governed solely by size exclusion, and the CEP and critical adsorption behavior cease to exist. This work fundamentally revises the understanding of polymer adsorption under critical conditions and provides a new framework for analyzing complex topological polymers, with implications for highly branched biological macromolecules such as starch and glycogen.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"32 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-06DOI: 10.1021/acs.macromol.5c03613
Alireza F. Behbahani
We study stress relaxation in several types of entangled monodisperse linear polymer melts by comparing the shear stress relaxation modulus, G(t), with the end-to-end vector autocorrelation function, P(t). The study includes three Kremer–Grest bead–spring models with varying chain stiffness, as well as a chemistry-specific coarse-grained model of cis-1,4-polybutadiene. For each model, multiple chain lengths were simulated, spanning a range of N/Ne = 5–50 entanglements per chain. We observe that in all cases the behavior of G(t), beyond the short-time Rouse regime, is accurately described by GN0[P(t)]2, where the chain-length-independent prefactor GN0 denotes the plateau modulus. This correlation is consistent with both double reptation and dynamic tube dilation models of polymer relaxation, each based on a distinct physical description. The double reptation model represents the melt as a transient network in which stress relaxation is governed by the survival probability of pairwise entanglements. The dynamic tube dilation model, however, assumes that the tube of constraints surrounding a polymer chain progressively enlarges as relaxation proceeds. The relation G(t) = GN0[P(t)]2 can serve as a basis for determining the plateau modulus and the corresponding entanglement length. It also simplifies the modeling of G(t), since an accurate analytical expression for P(t) is sufficient to describe the long-time behavior of G(t). We further compare the simulation data for P(t) and G(t) with theoretical expressions.
{"title":"Stress Relaxation in Monodisperse Entangled Polymer Melts: Correlation between Viscoelastic Response and Single-Chain Relaxation via Molecular Dynamics Simulations","authors":"Alireza F. Behbahani","doi":"10.1021/acs.macromol.5c03613","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03613","url":null,"abstract":"We study stress relaxation in several types of entangled monodisperse linear polymer melts by comparing the shear stress relaxation modulus, <i>G</i>(<i>t</i>), with the end-to-end vector autocorrelation function, <i>P</i>(<i>t</i>). The study includes three Kremer–Grest bead–spring models with varying chain stiffness, as well as a chemistry-specific coarse-grained model of <i>cis</i>-1,4-polybutadiene. For each model, multiple chain lengths were simulated, spanning a range of <i>N</i>/<i>N</i><sub>e</sub> = 5–50 entanglements per chain. We observe that in all cases the behavior of <i>G</i>(<i>t</i>), beyond the short-time Rouse regime, is accurately described by <i>G</i><sub>N</sub><sup>0</sup>[<i>P</i>(<i>t</i>)]<sup>2</sup>, where the chain-length-independent prefactor <i>G</i><sub>N</sub><sup>0</sup> denotes the plateau modulus. This correlation is consistent with both double reptation and dynamic tube dilation models of polymer relaxation, each based on a distinct physical description. The double reptation model represents the melt as a transient network in which stress relaxation is governed by the survival probability of pairwise entanglements. The dynamic tube dilation model, however, assumes that the tube of constraints surrounding a polymer chain progressively enlarges as relaxation proceeds. The relation <i>G</i>(<i>t</i>) = <i>G</i><sub>N</sub><sup>0</sup>[<i>P</i>(<i>t</i>)]<sup>2</sup> can serve as a basis for determining the plateau modulus and the corresponding entanglement length. It also simplifies the modeling of <i>G</i>(<i>t</i>), since an accurate analytical expression for <i>P</i>(<i>t</i>) is sufficient to describe the long-time behavior of <i>G</i>(<i>t</i>). We further compare the simulation data for <i>P</i>(<i>t</i>) and <i>G</i>(<i>t</i>) with theoretical expressions.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"29 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-06DOI: 10.1021/acs.macromol.5c03211
Saiprasad Gochhayat, Scott T. Milner
Two conflicting models have been advanced to describe water transport in membranes. The solution diffusion model postulates that water molecules diffuse independently down chemical potential gradients; the pore flow model envisions water as flowing collectively through pores, driven by a pressure gradient. To resolve this conflict, we conduct nonequilibrium molecular dynamics simulations of water transport in membranes with different water contents. Unlike previous works, we simulate a wet membrane in periodic boundary conditions, and drive the flow with a constant force per water molecule. For the same force per water molecule, water flows faster in wetter membranes, consistent with collective transport. To relate the transport to the pore flow picture, we measure the pore dimensions both structurally, by quantifying the ratios between “surface” and “bulk” water, and dynamically, by measuring spatial correlations of the drift velocity. The two measures are consistent, increase with membrane wetness, and generally support the pore flow picture.
{"title":"Water Flows Collectively in Simulated Ion Exchange Membranes","authors":"Saiprasad Gochhayat, Scott T. Milner","doi":"10.1021/acs.macromol.5c03211","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03211","url":null,"abstract":"Two conflicting models have been advanced to describe water transport in membranes. The solution diffusion model postulates that water molecules diffuse independently down chemical potential gradients; the pore flow model envisions water as flowing collectively through pores, driven by a pressure gradient. To resolve this conflict, we conduct nonequilibrium molecular dynamics simulations of water transport in membranes with different water contents. Unlike previous works, we simulate a wet membrane in periodic boundary conditions, and drive the flow with a constant force per water molecule. For the same force per water molecule, water flows faster in wetter membranes, consistent with collective transport. To relate the transport to the pore flow picture, we measure the pore dimensions both structurally, by quantifying the ratios between “surface” and “bulk” water, and dynamically, by measuring spatial correlations of the drift velocity. The two measures are consistent, increase with membrane wetness, and generally support the pore flow picture.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"33 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-05DOI: 10.1021/acs.macromol.5c03445
Amir Suhail, Olga Kuksenok
Cross-linked polyethylene networks (XLPEs) often exhibit enhanced performance and durability compared to their thermoplastic counterparts. Using coarse-grained molecular dynamics simulations, we capture the crystallization and melting of XLPEs during continuous cooling and heating. We track the evolution of stems, folds, ties, and tails and quantify cross-links partitioning between them during cooling. While most cross-links are localized within ties, their fraction embedded within stems gradually increases upon cooling, contributing to the maximum stem length exceeding the junction spacing, Nx. The partitioning of cross-links between folds and tails depends strongly on Nx, while the fractions of cross-links in stems and ties remain comparable for all cross-link densities considered. Further, we show that a decrease in Nx results in lower average stem length and reduced crystallization and melting temperatures. Our findings reveal how cross-links influence the development of crystalline domains in XLPEs, providing insights for further optimization of their properties and performance.
{"title":"Crystallization and Melting in Cross-Linked Polyethylene: Effect of Network Junctions on Stems, Ties, and Folds","authors":"Amir Suhail, Olga Kuksenok","doi":"10.1021/acs.macromol.5c03445","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03445","url":null,"abstract":"Cross-linked polyethylene networks (XLPEs) often exhibit enhanced performance and durability compared to their thermoplastic counterparts. Using coarse-grained molecular dynamics simulations, we capture the crystallization and melting of XLPEs during continuous cooling and heating. We track the evolution of stems, folds, ties, and tails and quantify cross-links partitioning between them during cooling. While most cross-links are localized within ties, their fraction embedded within stems gradually increases upon cooling, contributing to the maximum stem length exceeding the junction spacing, <i>N</i><sub><i>x</i></sub>. The partitioning of cross-links between folds and tails depends strongly on <i>N</i><sub><i>x</i></sub>, while the fractions of cross-links in stems and ties remain comparable for all cross-link densities considered. Further, we show that a decrease in <i>N</i><sub><i>x</i></sub> results in lower average stem length and reduced crystallization and melting temperatures. Our findings reveal how cross-links influence the development of crystalline domains in XLPEs, providing insights for further optimization of their properties and performance.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"48 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147359969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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