Pub Date : 2026-02-09DOI: 10.1021/acs.macromol.5c03427
Wensheng Duan,Shuo Zhao,Yeqian Wen,Zhongyu Duan,Li Zhang,Binyuan Liu
Developing dilution-tolerant organoborane catalysts for efficient CO2/propylene oxide (PO) copolymerization remains a key challenge. Herein, we report a cyclic anhydride (CA)-enhanced active species strategy that dramatically improves the performance of Lewis pairs comprising Lewis acid (triethylborane, Et3B) and diverse Lewis bases (LBs) such as triaminophosphines, tertiary amines, and tertiary phosphines. This approach features excellent operational simplicity and broad applicability. The optimized catalytic system enables exceptional dilution tolerance (PO/LB = 10,000:1), delivering a record productivity of 1.1 kg polymer per g catalyst at 80 °C. It also operates efficiently at 100 °C, exhibiting a 24-fold higher activity (turnover frequency = 1159 h–1) with high poly(propylene carbonate) selectivity (84%). Mechanistic insights indicate that CA-derived zwitterions are crucial, where the onium cation activates the epoxide and stabilizes the propagating chain end in cooperation with Et3B, while the carboxylate initiates polymerization. This work provides a general paradigm for designing highly active organoboron catalysts via in situ zwitterion engineering, enabling the scalable production of CO2-based polymers in a green manner.
{"title":"Dilution-Tolerant Organoboron Catalyst for the Copolymerization of CO2 and Propylene Oxide Enabled by a Cyclic Anhydride","authors":"Wensheng Duan,Shuo Zhao,Yeqian Wen,Zhongyu Duan,Li Zhang,Binyuan Liu","doi":"10.1021/acs.macromol.5c03427","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03427","url":null,"abstract":"Developing dilution-tolerant organoborane catalysts for efficient CO2/propylene oxide (PO) copolymerization remains a key challenge. Herein, we report a cyclic anhydride (CA)-enhanced active species strategy that dramatically improves the performance of Lewis pairs comprising Lewis acid (triethylborane, Et3B) and diverse Lewis bases (LBs) such as triaminophosphines, tertiary amines, and tertiary phosphines. This approach features excellent operational simplicity and broad applicability. The optimized catalytic system enables exceptional dilution tolerance (PO/LB = 10,000:1), delivering a record productivity of 1.1 kg polymer per g catalyst at 80 °C. It also operates efficiently at 100 °C, exhibiting a 24-fold higher activity (turnover frequency = 1159 h–1) with high poly(propylene carbonate) selectivity (84%). Mechanistic insights indicate that CA-derived zwitterions are crucial, where the onium cation activates the epoxide and stabilizes the propagating chain end in cooperation with Et3B, while the carboxylate initiates polymerization. This work provides a general paradigm for designing highly active organoboron catalysts via in situ zwitterion engineering, enabling the scalable production of CO2-based polymers in a green manner.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"90 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138954","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}
Achieving dynamic control of phosphorescence in polymer materials remains challenging due to the inherent conflict between the rigid matrix required to stabilize long-lived triplet excitons and the network plasticity necessary for dynamic editing. Herein, we report a neuromorphic phosphorescence-plastic hydrogel based on a poly(acrylamide-co-acrylonitrile) network whose luminescence can be spatially and temporally reconfigured through a frustrated phase separation mechanism. Under mild thermal training, the system undergoes a reversible phase transition, forming cyano-rich clusters in polymer-dense regions as intrinsic phosphorescent centers. The phase-separated structure expels water from between chains, promoting aggregation and suppressing nonradiative transitions, thereby promoting phosphorescence emission. This process enables the creation of fully rewritable phosphorescent patterns featuring a tunable afterglow duration of up to 5.0 s, repeatable erasure, and excellent water stability. The emission intensity and duration can be precisely regulated by varying the thermal input time, emulating memory consolidation and loss behaviors observed in neural systems. We further demonstrate applications in multilevel information encryption and dynamic displays. This work provides a polymer physics strategy for designing editable phosphorescent materials via controlled nonequilibrium network states, offering a pathway to bridge neuromorphic functions with soft matter photonics.
{"title":"Phosphorescence-Plastic Hydrogel Driven by Frustrated Phase Separation","authors":"Zhengdao Zhu,Xinzhen Fan,Yijie Jin,Zhiheng Zhou,Chuanzhuang Zhao","doi":"10.1021/acs.macromol.5c03276","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03276","url":null,"abstract":"Achieving dynamic control of phosphorescence in polymer materials remains challenging due to the inherent conflict between the rigid matrix required to stabilize long-lived triplet excitons and the network plasticity necessary for dynamic editing. Herein, we report a neuromorphic phosphorescence-plastic hydrogel based on a poly(acrylamide-co-acrylonitrile) network whose luminescence can be spatially and temporally reconfigured through a frustrated phase separation mechanism. Under mild thermal training, the system undergoes a reversible phase transition, forming cyano-rich clusters in polymer-dense regions as intrinsic phosphorescent centers. The phase-separated structure expels water from between chains, promoting aggregation and suppressing nonradiative transitions, thereby promoting phosphorescence emission. This process enables the creation of fully rewritable phosphorescent patterns featuring a tunable afterglow duration of up to 5.0 s, repeatable erasure, and excellent water stability. The emission intensity and duration can be precisely regulated by varying the thermal input time, emulating memory consolidation and loss behaviors observed in neural systems. We further demonstrate applications in multilevel information encryption and dynamic displays. This work provides a polymer physics strategy for designing editable phosphorescent materials via controlled nonequilibrium network states, offering a pathway to bridge neuromorphic functions with soft matter photonics.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"9 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138955","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 : 2026-02-09DOI: 10.1021/acs.macromol.5c03255
Aristotle F. Grosz,Julian Richardson,Tai Xuan Tan,Gabrielle Moore,Cassiano G. Aimoli,Benny D. Freeman,Zachary P. Smith
Penetrant-induced plasticization remains a significant limitation in membrane-based separation technologies, particularly in applications involving condensable species such as CO2 and heavy hydrocarbons. Traditional glassy polymer membranes often suffer performance losses under such conditions, while fluoropolymers have shown promise due to their high permselectivity, sorption characteristics, and potential resistance to plasticization and physical aging. In this study, a series of structurally analogous poly(ether imide)s with systematically varied fluorine contents were evaluated for CO2 transport properties. Sorption and permeability measurements of CO2 were conducted at pressures up to 51 atm at 35 °C and 10 atm at 260 °C. No plasticization pressures were observed at lower temperatures. However, diffusivity data suggest that the absence of fluorine moieties slightly increased the susceptibility to plasticization. This effect is suspected to be an indirect consequence of the increased glassiness in the fluoropolymer material. A review of relevant literature data suggests that increasing glass transition temperature was found to significantly reduce plasticization susceptibility across multiple families of polymers. The hydrocarbon polymer exhibited a higher temperature dependence on permeability, which is reflected in its elevated activation energy of permeation. Additionally, dilatometry studies revealed that the perfluoropolymer had a significantly lower CO2 partial molar volume compared to its hydrocarbon counterpart.
{"title":"CO2 Dilation and Transport Characterization of Incrementally Fluorinated Poly(ether imide) Membranes","authors":"Aristotle F. Grosz,Julian Richardson,Tai Xuan Tan,Gabrielle Moore,Cassiano G. Aimoli,Benny D. Freeman,Zachary P. Smith","doi":"10.1021/acs.macromol.5c03255","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03255","url":null,"abstract":"Penetrant-induced plasticization remains a significant limitation in membrane-based separation technologies, particularly in applications involving condensable species such as CO2 and heavy hydrocarbons. Traditional glassy polymer membranes often suffer performance losses under such conditions, while fluoropolymers have shown promise due to their high permselectivity, sorption characteristics, and potential resistance to plasticization and physical aging. In this study, a series of structurally analogous poly(ether imide)s with systematically varied fluorine contents were evaluated for CO2 transport properties. Sorption and permeability measurements of CO2 were conducted at pressures up to 51 atm at 35 °C and 10 atm at 260 °C. No plasticization pressures were observed at lower temperatures. However, diffusivity data suggest that the absence of fluorine moieties slightly increased the susceptibility to plasticization. This effect is suspected to be an indirect consequence of the increased glassiness in the fluoropolymer material. A review of relevant literature data suggests that increasing glass transition temperature was found to significantly reduce plasticization susceptibility across multiple families of polymers. The hydrocarbon polymer exhibited a higher temperature dependence on permeability, which is reflected in its elevated activation energy of permeation. Additionally, dilatometry studies revealed that the perfluoropolymer had a significantly lower CO2 partial molar volume compared to its hydrocarbon counterpart.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"32 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138956","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}
Chemoselective polymerization of divinyl monomers enables the synthesis of polymers bearing reactive side chains, which are versatile precursors for functionalized polymers and nonlinear architectures. However, retaining the highly polymerizable functional groups, such as α,β-unsaturated carbonyls, during polymerization is challenging. In this study, the polymerization of 2-(acryloyloxy)ethyl methacrylate (1) using Lewis pair catalysts composed of B(C6F5)3 with PPh3 or PCy3 proceeded exclusively at the acryloyl moiety without cross-linking, thus retaining the methacryloyl group in the polymer side chain. Nuclear magnetic resonance spectroscopy and density functional theory computations revealed that the complete chemoselectivity of this reaction, preferentially occurring at the acryloyl moiety rather than the methacryloyl moiety, could be attributed to the conformational preference of the 1–B(C6F5)3 complexes. Specifically, a highly electrophilic s-trans conformer formed upon coordination of the acryloyl group, whereas a much less reactive s-cis conformer formed upon coordination of the methacryloyl group. Additionally, acrylic copolymers of 1 bearing multiple methacryloyl groups were synthesized and employed as polymeric cross-linkers for the radical photopolymerization of ethyl acrylate (EA). The resulting polyEA elastomers exhibited increased stress at high strains and greater mechanical robustness than elastomers synthesized from a divinyl cross-linker.
{"title":"Chemoselective Polymerization of 2-(Acryloyloxy)ethyl Methacrylate Enabled by B(C6F5)3-Stabilized s-cis and s-trans Monomer Conformations","authors":"Masatoshi Deshimaru,Mikihiro Hayashi,Yoshihito Inai,Shin-ichi Matsuoka","doi":"10.1021/acs.macromol.5c02678","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c02678","url":null,"abstract":"Chemoselective polymerization of divinyl monomers enables the synthesis of polymers bearing reactive side chains, which are versatile precursors for functionalized polymers and nonlinear architectures. However, retaining the highly polymerizable functional groups, such as α,β-unsaturated carbonyls, during polymerization is challenging. In this study, the polymerization of 2-(acryloyloxy)ethyl methacrylate (1) using Lewis pair catalysts composed of B(C6F5)3 with PPh3 or PCy3 proceeded exclusively at the acryloyl moiety without cross-linking, thus retaining the methacryloyl group in the polymer side chain. Nuclear magnetic resonance spectroscopy and density functional theory computations revealed that the complete chemoselectivity of this reaction, preferentially occurring at the acryloyl moiety rather than the methacryloyl moiety, could be attributed to the conformational preference of the 1–B(C6F5)3 complexes. Specifically, a highly electrophilic s-trans conformer formed upon coordination of the acryloyl group, whereas a much less reactive s-cis conformer formed upon coordination of the methacryloyl group. Additionally, acrylic copolymers of 1 bearing multiple methacryloyl groups were synthesized and employed as polymeric cross-linkers for the radical photopolymerization of ethyl acrylate (EA). The resulting polyEA elastomers exhibited increased stress at high strains and greater mechanical robustness than elastomers synthesized from a divinyl cross-linker.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"295 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138957","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 : 2026-02-07DOI: 10.1021/acs.macromol.5c03473
Jian Song, Shanshan Xu, Chenxuan Sun, Bao Wang, Ying Zheng, Jian Zhou, Junfeng Liu, Chengtao Yu, Pengju Pan
Post-stretching of polymers often starts from a low-crystallized state in real processing. Unlike the glassy or fully crystallized polymers, the stretch-induced structural evolutions of low-crystallized polymers are much more complex due to the interplay between the pre-existing crystals and the surrounding glassy phase. Herein, we use stereocomplex (SC)-containing poly(lactic acid) (PLA) as a model low-crystallized system and investigated its structural evolutions and deformation mechanism during near-Tg stretching. A low amount of SCs was introduced into glassy PLA through the SC crystallization of l- and d-configured PLAs, and these SCs form physical networks in the polymer matrix. Both the glassy and SC-containing PLAs show rubber-like deformation behavior under stretching, while the presence of the SC network improves the strength, modulus, and toughness of the PLA matrix. In the near-Tg stretching process, the glassy PLA shows slower chain orientation kinetics, delayed formation of homocrystals (HCs) or a mesophase, and the later initiation of cavitation. With the introduction of the pre-existing SC network in glassy PLAs, the chain orientation kinetics and formation of HCs or a mesophase are highly accelerated, and cavitation is more significant under stretching. Such unique structural evolution behavior offers the strengthening and toughening effects of the pre-existing SC network on the PLA matrix. This study provides deep molecular insights for the post-stretching processing of glassy and partially crystallized polymers.
{"title":"Mechanical Strengthening, Facilitated Crystallization, and Microstructural Evolutions of Poly(lactic acid) during Near-Tg Stretching Induced by a Stereocomplex Crystal Network","authors":"Jian Song, Shanshan Xu, Chenxuan Sun, Bao Wang, Ying Zheng, Jian Zhou, Junfeng Liu, Chengtao Yu, Pengju Pan","doi":"10.1021/acs.macromol.5c03473","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03473","url":null,"abstract":"Post-stretching of polymers often starts from a low-crystallized state in real processing. Unlike the glassy or fully crystallized polymers, the stretch-induced structural evolutions of low-crystallized polymers are much more complex due to the interplay between the pre-existing crystals and the surrounding glassy phase. Herein, we use stereocomplex (SC)-containing poly(lactic acid) (PLA) as a model low-crystallized system and investigated its structural evolutions and deformation mechanism during near-<i>T</i><sub>g</sub> stretching. A low amount of SCs was introduced into glassy PLA through the SC crystallization of <span>l</span>- and <span>d</span>-configured PLAs, and these SCs form physical networks in the polymer matrix. Both the glassy and SC-containing PLAs show rubber-like deformation behavior under stretching, while the presence of the SC network improves the strength, modulus, and toughness of the PLA matrix. In the near-<i>T</i><sub>g</sub> stretching process, the glassy PLA shows slower chain orientation kinetics, delayed formation of homocrystals (HCs) or a mesophase, and the later initiation of cavitation. With the introduction of the pre-existing SC network in glassy PLAs, the chain orientation kinetics and formation of HCs or a mesophase are highly accelerated, and cavitation is more significant under stretching. Such unique structural evolution behavior offers the strengthening and toughening effects of the pre-existing SC network on the PLA matrix. This study provides deep molecular insights for the post-stretching processing of glassy and partially crystallized polymers.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"9 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135531","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 : 2026-02-06DOI: 10.1021/acs.macromol.5c02416
Soumyadeep Chowdhury, Swagata Pahari, Biswanath Guria, Amit Kumar Sen, Kanhaiya Lal Anjana, Prasenjit Ghosh, Rabindra Mukhopadhyay
Understanding how sulfur crosslinking architecture influences the properties of styrene–butadiene rubber (SBR) is critical for optimizing tire performance and durability. Our study employs all-atom molecular dynamics (MD) simulations and experimental validations to systematically investigate the impact of crosslinking density and sulfur crosslink types (monosulfide, disulfide, and polysulfide) on the structural, thermodynamic, dynamical, mechanical, and thermal properties of SBR. The computational framework is designed to enable precise control over network architecture, allowing the effects of crosslink length and density to be isolated─an approach not readily achievable in experimental settings. The models are validated by comparing simulated glass-transition temperatures (Tg) and densities with experimental data. An increase in Tg with crosslinking density and sulfur chain length was observed, consistent with reduced chain mobility. Thermodynamic properties such as thermal expansion coefficient, isothermal compressibility, adiabatic bulk modulus, and specific heat capacity were determined, revealing that higher crosslinking densities generally enhance thermal stability and mechanical rigidity, with subtle differences among crosslink types. Notably, the presence of intrachain crosslinks in polysulfide systems introduced additional constraints, affecting both thermal conductivity and chain dynamics. Stress–strain simulations indicated that mechanical strength primarily depends on crosslinking density, with minimal sensitivity to crosslink type. Our findings provide molecular level insights into how crosslinking architecture governs the macroscopic behavior of vulcanized SBR, offering valuable guidance for the rational design of advanced tire compounds.
{"title":"From Molecular Architecture to Performance: Structure–Property Correlations in Crosslinked SBR Explored through a Combined Experimental and Molecular Simulation Approach","authors":"Soumyadeep Chowdhury, Swagata Pahari, Biswanath Guria, Amit Kumar Sen, Kanhaiya Lal Anjana, Prasenjit Ghosh, Rabindra Mukhopadhyay","doi":"10.1021/acs.macromol.5c02416","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c02416","url":null,"abstract":"Understanding how sulfur crosslinking architecture influences the properties of styrene–butadiene rubber (SBR) is critical for optimizing tire performance and durability. Our study employs all-atom molecular dynamics (MD) simulations and experimental validations to systematically investigate the impact of crosslinking density and sulfur crosslink types (monosulfide, disulfide, and polysulfide) on the structural, thermodynamic, dynamical, mechanical, and thermal properties of SBR. The computational framework is designed to enable precise control over network architecture, allowing the effects of crosslink length and density to be isolated─an approach not readily achievable in experimental settings. The models are validated by comparing simulated glass-transition temperatures (<i>T</i><sub>g</sub>) and densities with experimental data. An increase in <i>T</i><sub>g</sub> with crosslinking density and sulfur chain length was observed, consistent with reduced chain mobility. Thermodynamic properties such as thermal expansion coefficient, isothermal compressibility, adiabatic bulk modulus, and specific heat capacity were determined, revealing that higher crosslinking densities generally enhance thermal stability and mechanical rigidity, with subtle differences among crosslink types. Notably, the presence of intrachain crosslinks in polysulfide systems introduced additional constraints, affecting both thermal conductivity and chain dynamics. Stress–strain simulations indicated that mechanical strength primarily depends on crosslinking density, with minimal sensitivity to crosslink type. Our findings provide molecular level insights into how crosslinking architecture governs the macroscopic behavior of vulcanized SBR, offering valuable guidance for the rational design of advanced tire compounds.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"83 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146122185","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 : 2026-02-06DOI: 10.1021/acs.macromol.5c02926
Hongbing Chen, Jian Tang, Quan Chen, Yumi Matsumiya, Hiroshi Watanabe
Nonlinear shear behavior was examined for a representative dually cross-linked elastomer, poly(vinyl alcohol) (PVA)/Borax hydrogel having both permanent and transient cross-links, the former due to covalent bonds and the latter sustained by a complex of the hydroxy group and borate ion. The PVA chain backbone between the transient cross-links behaved as the transient network strand partially relaxing on thermal dissociation and/or mechanical breakage of the transient cross-links. For comparison, the nonlinear behavior was also examined for bulk SI(COOH)S block copolymer having glassy spherical domains of the S block as the permanent end-cross-links for the I blocks and the hydrogen bonds between carboxyl groups as the transient cross-links. The I block backbone between the carboxyl groups served as the transient network strands. Experiments revealed significant shear-softening of the PVA/Borax hydrogel even under a very slow and small shear deformation characterized with the Weissenberg number Wi = 0.2 and the total shear strain γm = 0.03. Namely, the linear viscoelastic (LVE) responses of this gel vanished even under very mild shear conditions. The SI(COOH)S copolymer showed softening of a similar magnitude but under stronger shear conditions, Wi = 4.6 and γm = 2.0. These nonlinear features can be related to the shear-induced breakage of the transient cross-links that results in anisotropy of the population of the network strands reformed in different directions as well as nonequilibrium motion of the strands connected to the broken transient cross-links. The difference between the PVA/Borax hydrogel and the SI(COOH)S copolymer, the nonlinearity much stronger for the former, could be related to the mobility of the transient cross-links (–OH/borate ion complex) along the PVA backbone and lack of the mobility of the carboxyl group along the I block backbone.
{"title":"Nonlinear Rheological Behavior of Dually Cross-Linked Elastomers on Start-Up and Cessation of Shear Deformation","authors":"Hongbing Chen, Jian Tang, Quan Chen, Yumi Matsumiya, Hiroshi Watanabe","doi":"10.1021/acs.macromol.5c02926","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c02926","url":null,"abstract":"Nonlinear shear behavior was examined for a representative dually cross-linked elastomer, poly(vinyl alcohol) (PVA)/Borax hydrogel having both permanent and transient cross-links, the former due to covalent bonds and the latter sustained by a complex of the hydroxy group and borate ion. The PVA chain backbone between the transient cross-links behaved as the transient network strand partially relaxing on thermal dissociation and/or mechanical breakage of the transient cross-links. For comparison, the nonlinear behavior was also examined for bulk SI(COOH)S block copolymer having glassy spherical domains of the S block as the permanent end-cross-links for the I blocks and the hydrogen bonds between carboxyl groups as the transient cross-links. The I block backbone between the carboxyl groups served as the transient network strands. Experiments revealed significant shear-softening of the PVA/Borax hydrogel even under a very slow and small shear deformation characterized with the Weissenberg number <i>Wi</i> = 0.2 and the total shear strain γ<sub>m</sub> = 0.03. Namely, the linear viscoelastic (LVE) responses of this gel vanished even under very mild shear conditions. The SI(COOH)S copolymer showed softening of a similar magnitude but under stronger shear conditions, <i>Wi</i> = 4.6 and γ<sub>m</sub> = 2.0. These nonlinear features can be related to the shear-induced breakage of the transient cross-links that results in anisotropy of the population of the network strands reformed in different directions as well as nonequilibrium motion of the strands connected to the broken transient cross-links. The difference between the PVA/Borax hydrogel and the SI(COOH)S copolymer, the nonlinearity much stronger for the former, could be related to the mobility of the transient cross-links (–OH/borate ion complex) along the PVA backbone and lack of the mobility of the carboxyl group along the I block backbone.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"151 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146122513","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 broad applicability requires polyethylene (PE) to possess good processability and mechanical properties; direct synthesis of bimodal or multimodal PEs using a well-defined catalyst is therefore of considerable academic and industrial interest. In this paper, a series of dibenzobarrelene-derived α-diimine nickel complexes with a substituted 8-(p-R-phenyl)naphthylamine (R = OMe, Me, CF3) and a naphthylamine were designed and synthesized for ethylene polymerization by unsymmetric and hybrid aniline strategies. At low temperature (<50 °C), bimodal PEs are obtained because of the presence of syn and anti diastereomers of α-diimine nickel catalysts. At high temperatures (>65 °C), multimodal PEs with broad molecular weight distributions are produced, which arises from the cooperative contributions of syn/anti diastereomers of α-diimine nickel catalysts and imine metathesis. The imine metathesis observed for these hybrid α-diimine nickel complexes provides a new mechanistic perspective on their unique ethylene polymerization behavior and a strategy for tailoring PE molecular weight distributions by using well-defined catalysts.
{"title":"Multimodal Polyethylenes Produced by Hybrid and Unsymmetric α-Diimine Nickel Catalysts: The Roles of Syn/Anti Diastereomers and Imine Metathesis","authors":"Zonglin Qiu, Heng Gao, Chunyu Feng, Bo Ning, Cheng Zhang, Handou Zheng, Haiyang Gao","doi":"10.1021/acs.macromol.5c03572","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03572","url":null,"abstract":"The broad applicability requires polyethylene (PE) to possess good processability and mechanical properties; direct synthesis of bimodal or multimodal PEs using a well-defined catalyst is therefore of considerable academic and industrial interest. In this paper, a series of dibenzobarrelene-derived α-diimine nickel complexes with a substituted 8-(<i>p</i>-R-phenyl)naphthylamine (R = OMe, Me, CF<sub>3</sub>) and a naphthylamine were designed and synthesized for ethylene polymerization by unsymmetric and hybrid aniline strategies. At low temperature (<50 °C), bimodal PEs are obtained because of the presence of syn and anti diastereomers of α-diimine nickel catalysts. At high temperatures (>65 °C), multimodal PEs with broad molecular weight distributions are produced, which arises from the cooperative contributions of syn/anti diastereomers of α-diimine nickel catalysts and imine metathesis. The imine metathesis observed for these hybrid α-diimine nickel complexes provides a new mechanistic perspective on their unique ethylene polymerization behavior and a strategy for tailoring PE molecular weight distributions by using well-defined catalysts.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"384 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146122514","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 : 2026-02-05DOI: 10.1021/acs.macromol.5c02656
María del Mar Ramos-Tejada, Alberto Martín-Molina, Daniel Montesinos, Luis Pérez-Mas, Manuel Quesada-Pérez
Nanogels (as well as other polymer networks) can absorb nanoparticles that give them new properties and expand their application possibilities. The resulting hybrid entities constitute a kind of polymer nanocomposites, which have become an emerging area of research. In this work, coarse-grained simulations have been used to study how certain properties of these nanocomposites (size, number of nanoparticles inside, net charge, and surface potential) change with temperature. Four nanocomposites with different values of charge anchored to the polymer network (known as bare charge) were simulated. The degree to which nanocomposites shrink and expel the particles they contain depends strongly on the bare charge, which, in turn, could be related to the pH in pH-sensitive micro- and nanogels. Our results also reveal that nanoparticles are responsible for nanocomposites exhibiting much richer and more complex behavior than nanogels. Furthermore, the strong correlations that nanoparticles experience when the polymer network shrinks should not be ignored in mean-field theories that try to predict how nanocomposites behave.
{"title":"Coarse-Grained Simulations of Thermosensitive Polymer Nanocomposites","authors":"María del Mar Ramos-Tejada, Alberto Martín-Molina, Daniel Montesinos, Luis Pérez-Mas, Manuel Quesada-Pérez","doi":"10.1021/acs.macromol.5c02656","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c02656","url":null,"abstract":"Nanogels (as well as other polymer networks) can absorb nanoparticles that give them new properties and expand their application possibilities. The resulting hybrid entities constitute a kind of polymer nanocomposites, which have become an emerging area of research. In this work, coarse-grained simulations have been used to study how certain properties of these nanocomposites (size, number of nanoparticles inside, net charge, and surface potential) change with temperature. Four nanocomposites with different values of charge anchored to the polymer network (known as bare charge) were simulated. The degree to which nanocomposites shrink and expel the particles they contain depends strongly on the bare charge, which, in turn, could be related to the pH in pH-sensitive micro- and nanogels. Our results also reveal that nanoparticles are responsible for nanocomposites exhibiting much richer and more complex behavior than nanogels. Furthermore, the strong correlations that nanoparticles experience when the polymer network shrinks should not be ignored in mean-field theories that try to predict how nanocomposites behave.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"51 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146122187","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 : 2026-02-05DOI: 10.1021/acs.macromol.5c03399
Min Wang, Jihang Yu, Yushu Tian, Jiadong Wang, Xuan Qin, Yonglai Lu
Fatigue-induced degradation of polyurethane elastomers (PUEs) significantly affects their long-term performance, yet the effect of the distribution state of hard domains on their fatigue durability remains poorly understood. In particular, the microstructural evolution under compression fatigue, especially when thermal effects are minimized, is scarcely studied. This study investigates how adjusting the hard segment content (HSC) regulates the distribution and hierarchical organization of hard domains. Low-frequency compression fatigue was employed to isolate purely mechanical damage mechanisms. This allows us to elucidate their influence on the fatigue behavior of PUEs. Characterization results show that the high-HSC sample (PU-H25) forms a continuous and highly ordered spherulitic hard segment network that carries most of the compressive load. However, this rigid architecture is susceptible to stress concentration, leading to progressive degradation of the hard network, and pronounced permanent deformation. In contrast, the low-HSC material (PU-H17) contains hard segments dispersed as isolated physical cross-links within the soft-segment matrix. Under cyclic loading, deformation is primarily accommodated by the soft phase, producing a progressive softening behavior. Although PU-H17 exhibits a larger initial strain, it demonstrates superior elastic recovery. The medium-HSC sample (PU-H21) develops a semicontinuous hard domain morphology that enables cooperative load transfer between hard and soft phases, resulting in the highest structural stability and the slowest fatigue-induced damage evolution. Overall, the results demonstrate that HSC is a key factor governing the fatigue response of PUEs by tailoring their microphase-separated morphology. As HSC increases, the dominant fatigue mechanism shifts from soft-phase-controlled stress dissipation, to cooperative load sharing between hard and soft phases, and finally to hard-phase-dominated load bearing and fracture. These mechanistic insights provide a basis for designing PUEs with tailored fatigue resistance for specific service conditions.
{"title":"Mechanical-Fatigue-Driven Hierarchical Structural Evolution in Polyurethane Elastomers with Different Hard Segment Contents","authors":"Min Wang, Jihang Yu, Yushu Tian, Jiadong Wang, Xuan Qin, Yonglai Lu","doi":"10.1021/acs.macromol.5c03399","DOIUrl":"https://doi.org/10.1021/acs.macromol.5c03399","url":null,"abstract":"Fatigue-induced degradation of polyurethane elastomers (PUEs) significantly affects their long-term performance, yet the effect of the distribution state of hard domains on their fatigue durability remains poorly understood. In particular, the microstructural evolution under compression fatigue, especially when thermal effects are minimized, is scarcely studied. This study investigates how adjusting the hard segment content (HSC) regulates the distribution and hierarchical organization of hard domains. Low-frequency compression fatigue was employed to isolate purely mechanical damage mechanisms. This allows us to elucidate their influence on the fatigue behavior of PUEs. Characterization results show that the high-HSC sample (PU-H25) forms a continuous and highly ordered spherulitic hard segment network that carries most of the compressive load. However, this rigid architecture is susceptible to stress concentration, leading to progressive degradation of the hard network, and pronounced permanent deformation. In contrast, the low-HSC material (PU-H17) contains hard segments dispersed as isolated physical cross-links within the soft-segment matrix. Under cyclic loading, deformation is primarily accommodated by the soft phase, producing a progressive softening behavior. Although PU-H17 exhibits a larger initial strain, it demonstrates superior elastic recovery. The medium-HSC sample (PU-H21) develops a semicontinuous hard domain morphology that enables cooperative load transfer between hard and soft phases, resulting in the highest structural stability and the slowest fatigue-induced damage evolution. Overall, the results demonstrate that HSC is a key factor governing the fatigue response of PUEs by tailoring their microphase-separated morphology. As HSC increases, the dominant fatigue mechanism shifts from soft-phase-controlled stress dissipation, to cooperative load sharing between hard and soft phases, and finally to hard-phase-dominated load bearing and fracture. These mechanistic insights provide a basis for designing PUEs with tailored fatigue resistance for specific service conditions.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":"88 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116130","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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