Macromolecules最新文献

{"title":"Elucidation of the Termination Mechanism of the Radical Polymerization of Isoprene","authors":"Naila Yamin, Masatoshi Tosaka, Shigeru Yamago","doi":"10.1021/acs.macromol.5c00705","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c00705","url":null,"abstract":"The termination mechanism in the radical polymerization of isoprene (Ip), a representative diene monomer, was investigated through product analyses formed by the reaction of polyisoprene (PIp) model radicals and structurally controlled PIp end radicals. The results revealed that the termination occurred exclusively by combination (<i>Comb</i>) with &gt;97% selectivity, regardless of the conditions, even in highly viscous media. This finding contrasts sharply with the termination mechanism in styrene polymerization, in which increasing viscosity shifts the termination mechanism entirely from <i>Comb</i> to disproportionation (<i>Disp</i>). Therefore, an extremely high propensity for <i>Comb</i> selectivity in Ip polymerization is demonstrated. Additionally, since Ip is used as a coupling agent in radical coupling reactions, these results also provide valuable insights into synthesizing new polymer materials based on IP-derived polymer end radical species.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"18 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897775","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}

{"title":"Paradox in Sintering of Nascent Ultrahigh Molecular Weight Polymers in the Solid State","authors":"Fuhai Zhou, Jiayi Zhao, Sanjay Rastogi","doi":"10.1021/acs.macromol.5c00731","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c00731","url":null,"abstract":"The sintering of ceramics, metals, and polymers has been a subject of intense interest, especially when the materials can be sintered without melting in the solid state. In contrast to inorganic materials, crystallizable polymers have segments of the same chain residing in crystalline and noncrystalline regions. The topological constraints between the chain segments residing in the noncrystalline region are strongly influenced by the crystallization and/or polymerization history. Here, we address the influence of topological constraints on the deformation of crystalline domains to the extent that lattice diffusion and grain boundary diffusion in semicrystalline polymers can be achieved without melting. This allows ease in translation of the macroscopic forces to the molecular length scale in the sintered polymer, facilitating uniaxial and biaxial deformation below the melting temperature. Since solid-state processing circumvents the challenges of melt processing, entropic relaxation of the oriented chains, and thermal degradation of the polymers at high temperatures, unprecedented mechanical properties in the uniaxial and biaxial drawn intractable ultrahigh molar mass polymers have been achieved. Thus, solvent-free sustainable solutions are provided for the processing of the intractable engineering polymers needed for demanding applications. The ease of sintering allows the fabrication of grain-boundary-free products, with advantages in prostheses.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"40 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143901144","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}

{"title":"Machine-Learning-Assisted Design of Mechanically Robust Room-Temperature Self-Healing Epoxy Resins","authors":"Haitao Wu, Hao Wang, Changcheng Wang, Zhaoyang Yuan, Hu Xu, Jing Zheng, Mengjin Jiang, Jinrong Wu","doi":"10.1021/acs.macromol.5c00667","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c00667","url":null,"abstract":"Epoxy resins are the most widely used thermosets, yet they typically lack the capability to self-heal at room temperature due to their molecular chains and networks being immobilized in a glassy state. Herein, machine learning identifies fractional free volume as a crucial factor for enabling self-healing in the glassy state. Guided by this insight, we designed an epoxy network incorporating dangling chains together with numerous hydrogen bonds and aromatic disulfide bonds. The dangling chains introduce large free volume, facilitating the reorganization of hydrogen bonds and the radical-mediated exchange of aromatic disulfide bonds, thereby imparting prominent self-healing capability at room temperature. Notably, the damaged epoxy not only can recover 81.2% of its tensile strength without intervention but also can autonomously and completely eliminate electrical tree damage and scratches at room temperature. Under mild compression, 100% healing occurs within tens of minutes in the glassy state. Additionally, the optimized epoxy exhibits high physicomechanical properties with a tensile strength of 42.1 MPa, a modulus of 2.9 GPa, and a glass transition temperature of 53.2 °C. Its ability to self-heal both electrical tree and mechanical damage at room temperature positions this epoxy as a promising material for advanced insulating and sealing applications.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"21 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897779","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}

{"title":"Effect of the Second Network on First Network Rupture and the Origin of Energy Dissipation in Double Network Hydrogels","authors":"Zhi Jian Wang, Gumi Wei, Tasuku Nakajima, Jian Ping Gong","doi":"10.1021/acs.macromol.5c00331","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c00331","url":null,"abstract":"The detection of mechanoradicals generated by homolytic bond scission enables the quantitative determination of the polymer network rupture during deformation in hydrogels. In this study, we investigate, in double network (DN) hydrogels, how the stretchable second network affects the stress distribution and rupture of the first network and how it contributes to energy dissipation by correlating bond scission with mechanical hysteresis. By increasing the second network density while keeping the first network constant, the tensile behavior of DN gels transitions from typical DN characteristics, exhibiting yielding with necking and strain-hardening, to an oversupported state, showing yielding and strain-hardening without necking, accompanied by reduced bond scission in the first network. Notably, the first network bond scission occurs extensively beyond the yield point and saturates at large strains, irrespective of necking behavior. Furthermore, the energy dissipated per bond cleavage remains constant in the necking regime but increases significantly in the strain-hardening regime and rises with higher second network density, indicating dissipation in the second network through internetwork entanglements. These trends are consistent across DN gels with both weak and strong cross-linkers in the first network, with the weak cross-linker leading to greater bond scission. This study not only deepens the understanding of the molecular mechanism underlying DN materials but also assists in designing mechanoresponsive functional materials based on DN mechanochemistry.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"53 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897777","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}

{"title":"Interfacial Tension of Graft Block Copolymers at Immiscible Homopolymer Interfaces","authors":"Ashutosh K. Nehete, Frank S. Bates, Kevin D. Dorfman","doi":"10.1021/acs.macromol.5c00306","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c00306","url":null,"abstract":"Graft multiblock copolymers are emerging as effective compatibilizers for immiscible polymer blends, leveraging the large parameter space offered by their branched architecture to surpass traditional linear diblock copolymers in compatibilization potential. We report the results of coarse-grained molecular dynamics simulations of AB graft copolymers at a strongly segregated A/B interface, focusing on the impact of graft copolymer loading at the interface and the copolymer architecture on the resulting interfacial tension of the system, which is correlated to copolymer conformation. At relatively low copolymer loadings, distributing the total grafting beads into a greater number of grafts enhances the copolymer interfacial coverage, effectively minimizing unfavorable homopolymer-homopolymer contacts and reducing interfacial tension. At relatively high copolymer loadings, once the interface is saturated with copolymers, molecules with a high number of grafts exhibit a greater penetration perpendicular to the interface, characterized by bending of the backbone and increased deviation of backbone beads from the interfacial plane. Our results demonstrate the existence of an optimal junction density beyond which the copolymers aggregate at the interface, leading to a plateau in interfacial tension as junction density increases further.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"3 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897776","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}

{"title":"CO2-Triggered Hydrogelation: Architectural Insights from Random and Graft Polyelectrolytes","authors":"Dianguo Wu, Yan Zhang, James Doutch, Peixun Li, Xuezhi Zhao, Yujun Feng","doi":"10.1021/acs.macromol.5c00708","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c00708","url":null,"abstract":"The sol–gel transition of CO₂-responsive polyelectrolytes is driven by electrostatic interactions between anionic groups and protonated cationic moieties, yet the critical roles of ionic stoichiometry and spatial architecture in mediating gelation behavior remain poorly understood. To address this knowledge gap, two distinct copolymer series with varying configurations and anion/CO₂-responsive monomer ratios were synthesized: P(AA-<i>co</i>-DPM) random copolymers via free radical copolymerization of acrylamide, acrylic acid, and dimethylaminopropyl methacrylamide (DMAPMAm), while PAA-<i>g</i>-PDPM graft copolymers through the covalent attachment of poly(DMAPMAm) side chains to poly(AM-<i>co</i>-AA) backbones. CO₂-induced protonation led to contrasting phase behaviors contingent on ionic balance. For P(AA-<i>co</i>-DPM) aqueous solution, viscosity decreased when <i>n</i>_DMAPMAm ≤ 0.83<i>n</i>_NaAA, increased when <i>n</i>_DMAPMAm ≥ 1.13 <i>n</i>_NaAA, and resulted in precipitation when <i>n</i>_DMAPMAm = 0.83<i>n</i>_NaAA. Conversely, the PAA-<i>g</i>-PDPM aqueous solution exhibited continuous viscosity enhancement up to <i>n</i>_DMAPMAm ≤ 0.65<i>n</i>_NaAA, followed by dehydration at higher cationic ratios. Notably, the graft architecture demonstrated superior gelation under CO₂ exposure, forming robust hydrogels with frequency-independent modulus (0.01–0.1 rad·s^–1) and minimal energy dissipation (tan δ &lt; 0.1). In contrast, random copolymers yielded fragile networks displaying frequency-dependent moduli and elevated tan δ (&gt;0.1). Rheology-small angle neutron scattering analysis revealed that graft copolymers underwent CO₂-induced chain collapse from swollen to compact conformations, creating physical cross-links, whereas random chains maintained Gaussian statistics regardless of protonation state. These findings highlight that extended cationic side chains in graft architectures enhance intermolecular entanglement and directional electrostatic interactions, offering a strategic approach for designing CO₂-responsive hydrogels with tailored mechanical properties through molecular architecture engineering.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"90 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143893713","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}

{"title":"Homocoupling Defects in EDOT-Based Polymers: Their Impact on Solution Aggregation, Redox Behavior, and Electrical Conductivity","authors":"Spencer J. Gilman, Shamil Saiev, Jean-Luc Brédas, John R. Reynolds","doi":"10.1021/acs.macromol.5c00661","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c00661","url":null,"abstract":"Direct arylation polymerization (DArP) has emerged as an efficient method to lower the synthetic complexity of conjugated polymers. This work reports the preparation of an EDOT-based conjugated and electroactive polymer by two different DArP routes where the two paths differ by exchanging each monomer’s coupling functionality (−H vs −Br). It was found that the hydrogenated monomer was more likely to homocouple during polymerization, yielding two polymer samples of similar molecular weight and dispersity but different EDOT content. Then, a third polymer intentionally made with excess EDOT content was prepared by copolymerizing with biEDOT. It was found that increasing EDOT content, whether through homocoupling defects or copolymerization with biEDOT, resulted in materials that had lower oxidation potentials, stronger solution aggregation, and higher solid-state electrical conductivities after oxidative doping.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"24 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897778","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}

{"title":"Glass Transition and Yielding of Ultrasoft Charged Spherical Micelles","authors":"Roshan Akdar Mohamed Yunus, Utku Gürel, Aleksander Guzik, Philippe Dieudonné-George, Marc C.A. Stuart, Christos N. Likos, Patrizio Raffa, Domenico Truzzolillo, Andrea Giuntoli, Daniele Parisi","doi":"10.1021/acs.macromol.4c03215","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c03215","url":null,"abstract":"Colloids are widely used as model systems to study the glass transition, with much research focused on hard or soft neutral colloids and their mixtures. However, the glass transition of soft-charged spherical colloids and its dynamic effects remain underexplored. This study assesses the glass transition of polymeric multiarm charged soft colloids using shear rheology, coarse-grained molecular dynamics (MD) simulations, and X-ray scattering. Strong particle–particle correlations, driven by electrostatic interarm repulsion, inhibit Newtonian behavior in the dilute regime. The liquid-to-glass transition occurs at just 0.25 wt %, marked by weak caging and minimal interdigitation of arms, as evidenced by particle contact analysis in MD simulations and the strong frequency dependence of the dynamic moduli. Particle shells interdigitate only well within the glassy regime, leading to a nearly frequency-independent rheological response. The weak volume fraction dependence of the yield stress sets these charged systems among the softest colloids reported in the literature.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"223 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143889788","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}

{"title":"Ultrasonic Detection of the Interface Formation between the Polymer-Rich and Monomer-Rich Phases during Bulk Polymerization of Methyl Methacrylate","authors":"Naoki Mori, Akikazu Matsumoto, Yasuhito Suzuki","doi":"10.1021/acs.macromol.5c00268","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c00268","url":null,"abstract":"Polymeric materials are essential for a wide range of applications; however, understanding and controlling their reactive processing, especially in the later stages, remains challenging. One notable phenomenon in the polymerization of methyl methacrylate (MMA) via bulk radical polymerization is the Trommsdorff effect; this effect causes a rapid acceleration in the reaction rate, and its mechanism remains debatable. In this study, we investigated MMA polymerization by integrating ultrasonic monitoring, temperature tracking, and video recording. This approach enabled the observation of the formation of a polymer-rich phase and the propagation of the polymerization front. Contrary to the assumption that MMA undergoes homogeneous polymerization, our results revealed macroscopic heterogeneity during its transition from the liquid to the glassy state. The polymerization process can be categorized into six distinct stages based on its response to ultrasonic propagation. These results fundamentally enhance our understanding of bulk polymerization.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"21 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143893872","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}

{"title":"Thermo-Mechanics of PNIPAM Gels: from a Single Chain to a Network Response","authors":"Michal Levin, Noy Cohen","doi":"10.1021/acs.macromol.4c03233","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c03233","url":null,"abstract":"Poly(<i>N</i>-isopropylacrylamide) (PNIPAM) is a temperature-responsive polymer that exhibits a lower critical solution temperature (LCST) phase transition. On the chain level, this behavior stems from a coil-to-globule configurational transition at a critical temperature. On the macroscopic level, copolymerization or cross-linking of PNIPAM results in a hydrogel that decreases its volume significantly at the volume phase transition temperature (VPTT). This behavior is advantageous in a wide range of applications, including tissue engineering, drug delivery systems, and soft robotics. To fully exploit the unique properties of PNIPAM, it is important to understand the underlying mechanisms that govern its thermo-mechanical response. In this work we present a microscopically motivated energy-based model to explain the coil-to-globule transition in PNIPAM networks. We begin by considering a single chain below and above the LCST and employ tools from polymer physics to capture the water–polymer interactions and the role of water cages on the entropy. We present physically motivated parameters to describe the transition of a PNIPAM chain in response to temperature and an external force and validate our model against nanofishing experiments on single PNIPAM chains. To determine the macroscopic response, we employ the chain model and integrate from the chain to the network level. Our model illustrates the influence of the coil-to-globule transition on the decrease in volume of a PNIPAM gel as the temperature increases. As opposed to the classical approaches, in which the interaction parameter χ is taken as a function of temperature, the proposed model captures the transition at the chain level, which directly affects the macroscopic response. To demonstrate the merit of the model, we compare its predictions to experimental data on the volumetric deformations and the stress of traction free and of constrained PNIPAM networks. The findings from this work provide valuable insights into the molecular mechanisms that dominate the response of PNIPAM gels and provide fundamental tools for the design and optimization of PNIPAM-based gels for various applications.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"68 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143889853","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}