The microstructure of poly(vinyl alcohol) films formed during the solution drying process significantly influences their tensile ductility and optical transmittance. However, the “skin-core” structure of the dried PVA film is very obvious since the PVA solution dries extremely fast at a relatively low initial concentration (C0). Herein, we propose a strategy to reduce the evaporation rate through the incorporation of plasticizer-type additives. For this purpose, urea and diethanolamine (DEA) were selected as the compound additives. On the one hand, the solubility of urea in water was improved by DEA because DEA is a good solvent for urea. On the other hand, more intermolecular hydrogen bonds were formed between the primary amine groups on urea and the hydroxyl (−OH) groups on PVA. The formation of PVA–plasticizer hydrogen bonding networks significantly prolonged the deceleration drying period and slowed down the drying process of the solution. In addition, the reduction in the content of single hydrogen-bonded water also favored the acquisition of a homogeneous structure. When the content of the urea/DEA compound additives was over 10%, the “skin-core” structure was suppressed. The structural changes in films have had an impact on both mechanical and optical performances. The fracture strain of the modified PVA film reaches 448.2%, and the average light transmittance in the visible range reaches 97.8% when the content of the compound additive is 20% of the PVA mass. These values are much higher than those of the control film, which are 9.2 and 92.2%, respectively. This study enhances comprehension of the film-forming mechanism and structural changes in PVA/H2O/plasticizer systems, offering theoretical insights for improved industrial processing.
{"title":"Suppression of the Skin-Core Structure of Poly(vinyl alcohol) Films by Adding Urea/Diethanolamine to Improve the Mechanical and Optical Properties","authors":"Yinghan Li, Xuelei Liu, Dong Lv, Saiyin Hou, Xinhong Yu, Yanchun Han","doi":"10.1021/acs.macromol.4c00742","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00742","url":null,"abstract":"The microstructure of poly(vinyl alcohol) films formed during the solution drying process significantly influences their tensile ductility and optical transmittance. However, the “skin-core” structure of the dried PVA film is very obvious since the PVA solution dries extremely fast at a relatively low initial concentration (<i>C</i><sub>0</sub>). Herein, we propose a strategy to reduce the evaporation rate through the incorporation of plasticizer-type additives. For this purpose, urea and diethanolamine (DEA) were selected as the compound additives. On the one hand, the solubility of urea in water was improved by DEA because DEA is a good solvent for urea. On the other hand, more intermolecular hydrogen bonds were formed between the primary amine groups on urea and the hydroxyl (−OH) groups on PVA. The formation of PVA–plasticizer hydrogen bonding networks significantly prolonged the deceleration drying period and slowed down the drying process of the solution. In addition, the reduction in the content of single hydrogen-bonded water also favored the acquisition of a homogeneous structure. When the content of the urea/DEA compound additives was over 10%, the “skin-core” structure was suppressed. The structural changes in films have had an impact on both mechanical and optical performances. The fracture strain of the modified PVA film reaches 448.2%, and the average light transmittance in the visible range reaches 97.8% when the content of the compound additive is 20% of the PVA mass. These values are much higher than those of the control film, which are 9.2 and 92.2%, respectively. This study enhances comprehension of the film-forming mechanism and structural changes in PVA/H<sub>2</sub>O/plasticizer systems, offering theoretical insights for improved industrial processing.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141441621","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}
Allylic ylide polymerization is an unconventional method for synthesizing polymers with unique allylic repeat units. However, in contrast to significant efforts to develop new monomers, the development of new catalysts for this realm is scarce. Thus far, only organoboranes have been explored and proven to be efficient catalysts. Here, we demonstrate that aluminum-based catalysts, triethylaluminum (AlEt3), aluminum chloride (AlCl3), and aluminum bromide (AlBr3), are efficient for 2-methylallyl triphenyl arsonium ylide polymerization, affording poly(propenylenes) with high 1,3-monomeric insertion selectivity (>97.7%) and trans-configuration (>92.5%). The aluminum-mediated polymerizations proceed in an immortal manner, as evidenced by the controlled molecular weights (DPNMR), narrow polydispersities, and chain extension experiments. Interestingly, in the AlEt3-mediated polymerization, each Al atom produces three polymer chains, whereas in the cases of aluminum halides, one polymer chain per Al atom is observed due to the weak migration ability of halogen. On the basis of experimental results, an aluminum-mediated ylide polymerization mechanism is proposed. This mechanism involves halogen and [1,3]-aluminum migrations, which dictate the catalyst activity and product structures. Moreover, all C3 polymers exhibit nontraditional intrinsic luminescence. Incorporation of halogen atoms at the chain end significantly enhances the photoluminescence properties due to the improved stacking of polymeric segments through halogen-π interactions. This study presents a new approach for synthesizing α,ω-end-functionalized C3 polymers and also expands the potential for the rational design of efficient catalysts for ylide polymerizations.
{"title":"Aluminum-Mediated Polymerization of Allylic Ylides toward α,ω-Functionalized C3 Polymers with Enhanced Nontraditional Intrinsic Luminescence","authors":"Tongyao Zhao, Mingyi Liao, Yanming Hu, Guangyuan Zhou, Pibo Liu, Nikos Hadjichristidis","doi":"10.1021/acs.macromol.3c02516","DOIUrl":"https://doi.org/10.1021/acs.macromol.3c02516","url":null,"abstract":"Allylic ylide polymerization is an unconventional method for synthesizing polymers with unique allylic repeat units. However, in contrast to significant efforts to develop new monomers, the development of new catalysts for this realm is scarce. Thus far, only organoboranes have been explored and proven to be efficient catalysts. Here, we demonstrate that aluminum-based catalysts, triethylaluminum (AlEt<sub>3</sub>), aluminum chloride (AlCl<sub>3</sub>), and aluminum bromide (AlBr<sub>3</sub>), are efficient for 2-methylallyl triphenyl arsonium ylide polymerization, affording poly(propenylenes) with high 1,3-monomeric insertion selectivity (>97.7%) and <i>trans</i>-configuration (>92.5%). The aluminum-mediated polymerizations proceed in an immortal manner, as evidenced by the controlled molecular weights (DP<sub>NMR</sub>), narrow polydispersities, and chain extension experiments. Interestingly, in the AlEt<sub>3</sub>-mediated polymerization, each Al atom produces three polymer chains, whereas in the cases of aluminum halides, one polymer chain per Al atom is observed due to the weak migration ability of halogen. On the basis of experimental results, an aluminum-mediated ylide polymerization mechanism is proposed. This mechanism involves halogen and [1,3]-aluminum migrations, which dictate the catalyst activity and product structures. Moreover, all C3 polymers exhibit nontraditional intrinsic luminescence. Incorporation of halogen atoms at the chain end significantly enhances the photoluminescence properties due to the improved stacking of polymeric segments through halogen-π interactions. This study presents a new approach for synthesizing α,ω-end-functionalized C3 polymers and also expands the potential for the rational design of efficient catalysts for ylide polymerizations.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141436126","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}
Conducting polymers, despite their promising electrochromic properties, face limitations in smart windows due to their inverse modulation in visible and near-infrared (NIR) regions. In this study, we introduce novel “black-to-black” electrochromic copolymers, synthesized through direct arylation polymerization (DArP) of tris(thienothiophene) (TTT), 3,4-dialkylthiophene (DKTh), and benzo[c][1,2,5]thiadiazole (Tz) monomers. These copolymers demonstrate minimal visible impact (<5%) and broad NIR modulation (>60%). The resulting electrochromic devices seamlessly transition between “Warm” mode (low visible and high NIR transmittance) and “Dark” mode (low visible and NIR transmittance), showcasing high switching stability, open-circuit memory, and coloration efficiency. The synthesized copolymers and devices surpass conventional “color-to-transmissive” conducting polymers, exhibiting significant solar heat gain coefficient (SHGC) modulation and high optical contrast. This discovery prompts further exploration of dual-band electrochromic materials, particularly those featuring a “Warm” mode based on conducting polymers.
{"title":"“Dark-to-Warm” Smart Windows Enabled by Black-to-Black Electrochromic Copolymers with Minimal Visible and Remarkable NIR Modulation","authors":"Cheng Yuan, Guoqiang Kuang, Hongbin Yin, Akif Zeb, Pengrui Yin, Chaoyang Zhang, Yijie Tao, Yafei Guo, Shiguo Zhang","doi":"10.1021/acs.macromol.4c00483","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00483","url":null,"abstract":"Conducting polymers, despite their promising electrochromic properties, face limitations in smart windows due to their inverse modulation in visible and near-infrared (NIR) regions. In this study, we introduce novel “black-to-black” electrochromic copolymers, synthesized through direct arylation polymerization (DArP) of tris(thienothiophene) (TTT), 3,4-dialkylthiophene (DKTh), and benzo[c][1,2,5]thiadiazole (Tz) monomers. These copolymers demonstrate minimal visible impact (<5%) and broad NIR modulation (>60%). The resulting electrochromic devices seamlessly transition between “Warm” mode (low visible and high NIR transmittance) and “Dark” mode (low visible and NIR transmittance), showcasing high switching stability, open-circuit memory, and coloration efficiency. The synthesized copolymers and devices surpass conventional “color-to-transmissive” conducting polymers, exhibiting significant solar heat gain coefficient (SHGC) modulation and high optical contrast. This discovery prompts further exploration of dual-band electrochromic materials, particularly those featuring a “Warm” mode based on conducting polymers.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141436142","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}
Recent years have witnessed great achievements in the coordination polymerization of various olefins catalyzed by rare-earth metal catalysts. However, the ubiquitous monomers containing a benzocyclobutene (BCB) group, which have excellent thermal properties, remain unexplored yet. Here, we report the coordination (co)polymerization of 4-vinylbenzocyclobutene (4-VBCB) by using tetraphenylcyclopentadienyl supported scandium alkyl complex [(CpPh4H)Sc(CH2SiMe3)2(THF)] (1) as a precatalyst. The high syndioselectivity (rrrr > 99%) was observed in both the resultant poly(4-VBCB)s and poly(St-co-VBCB)s, which are soluble in most common solvents, sharply in contrast to the typical sPS. Copolymerization of 4-VBCB with styrene afforded a gradient copolymer due to the dramatically different reactivity of the two monomers (rVBCB/rSt = 84.3). Moreover, copolymerization of 4-VBCB with ethylene (2 atm) proceeded smoothly to yield ethylene-VBCB random copolymers with a variety of VBCB contents (5.2–22.7%). In the presence of maleimide, cross-linked functional polyethylene was obtained through the Diels–Alder reaction and intermolecular cross-link. More interestingly, nanoparticles based on polyethylene were successfully synthesized under ultralow concentration via intramolecular cross-linking of the ethylene-VBCB copolymer.
{"title":"Syndiotactic (Co)polymerization of 4-Vinylbenzocyclobutene Catalyzed by Rare-Earth Metal Complex","authors":"Peng Deng, Lipeng Sang, Xun Gong, Xiang Guo, Jianhua Cheng","doi":"10.1021/acs.macromol.4c00958","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00958","url":null,"abstract":"Recent years have witnessed great achievements in the coordination polymerization of various olefins catalyzed by rare-earth metal catalysts. However, the ubiquitous monomers containing a benzocyclobutene (BCB) group, which have excellent thermal properties, remain unexplored yet. Here, we report the coordination (co)polymerization of 4-vinylbenzocyclobutene (4-VBCB) by using tetraphenylcyclopentadienyl supported scandium alkyl complex [(Cp<sup>Ph4H</sup>)Sc(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(THF)] (<b>1</b>) as a precatalyst. The high syndioselectivity (rrrr > 99%) was observed in both the resultant poly(4-VBCB)s and poly(St-<i>co</i>-VBCB)s, which are soluble in most common solvents, sharply in contrast to the typical <i>s</i>PS. Copolymerization of 4-VBCB with styrene afforded a gradient copolymer due to the dramatically different reactivity of the two monomers (<i>r</i><sub>VBCB</sub>/<i>r</i><sub>St</sub> = 84.3). Moreover, copolymerization of 4-VBCB with ethylene (2 atm) proceeded smoothly to yield ethylene-VBCB random copolymers with a variety of VBCB contents (5.2–22.7%). In the presence of maleimide, cross-linked functional polyethylene was obtained through the Diels–Alder reaction and intermolecular cross-link. More interestingly, nanoparticles based on polyethylene were successfully synthesized under ultralow concentration <i>via</i> intramolecular cross-linking of the ethylene-VBCB copolymer.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141425302","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 : 2024-06-19DOI: 10.1021/acs.macromol.4c00607
Tae Yong Ha, Seung Heum Jeong, Chunggi Baig
We present a detailed analysis of the rheological behavior of entangled short-chain-branched (SCB) ring polymers at interfaces via direct comparison with the corresponding pure (unbranched) ring polymers using atomistic nonequilibrium molecular dynamics simulations of confined polyethylene melt systems under shear flow. To elucidate the general structural and dynamical characteristics of interfacial polymer chains, we analyze various physical properties of the chains in the bulk and interfacial regions separately within the confined systems, such as the chain radius of gyration and its distribution, the average streaming velocity profile, and the degree of interfacial slip, with respect to the applied flow strength. The pure ring polymer melt has a highly extended and aligned chain structure along the flow (x-)direction at the interface, even under weak flow fields, indicative of the strong wall effects via the attractive polymer–wall interactions. In contrast, the interfacial SCB ring chains generally form a compact structure like that of the corresponding bulk chains in the weak flow regime, representing a significant role of the short branches to effectively diminish the wall effect. In conjunction with these structural characteristics, the entangled SCB ring polymer melt displays a markedly smaller degree of interfacial slip than the corresponding pure ring analogue in the weak-to-intermediate flow regimes. Furthermore, while both the pure ring and the SCB ring polymer melt systems reveal similar fundamental molecular mechanisms at the interface with respect to the flow strength (i.e., z-to-x rotation, loop wagging, loop migration, and loop tumbling mechanisms), the SCB ring polymer melt displays relatively weaker loop migration and loop wagging dynamics with highly curvy backbone structures in the intermediate flow regime. In the strong flow regime, both the pure ring and SCB ring systems exhibit the loop tumbling mechanism together with intensive collisions between the interfacial chains and the wall. However, the interfacial SCB ring chains execute substantial loop migration dynamics even at high flow fields, which facilitates interfacial slip.
我们利用原子非平衡分子动力学模拟了剪切流下的密闭聚乙烯熔体体系，通过与相应的纯环聚合物（未支化）的直接比较，详细分析了缠结短链支化环聚合物在界面处的流变行为。为了阐明界面聚合物链的一般结构和动力学特征，我们分别分析了密闭体系中块状区和界面区聚合物链的各种物理性质，如链的回转半径及其分布、平均流速曲线以及界面滑移程度与所施加的流动强度的关系。即使在弱流场条件下，纯环聚合物熔体在界面上沿流动（x-）方向也具有高度延伸和排列整齐的链结构，这表明通过聚合物与壁的吸引力相互作用产生了强烈的壁效应。与此相反，界面 SCB 环链在弱流动条件下通常会形成与相应体链一样的紧凑结构，这表明短枝在有效减弱壁效应方面发挥了重要作用。结合这些结构特征，缠结 SCB 环聚合物熔体在弱到中间流动体系中的界面滑移程度明显小于相应的纯环类似物。此外，虽然纯环和 SCB 环聚合物熔体系统在界面上显示出与流动强度类似的基本分子机制（即 z 到 x 旋转、环摆动、环迁移和环翻滚机制），但 SCB 环聚合物熔体在中间流动体系中显示出相对较弱的环迁移和环摆动动态，并具有高度弯曲的骨架结构。在强流动体系中，纯环和 SCB 环体系都表现出翻滚机制，同时界面链与壁之间会发生激烈碰撞。然而，即使在高流动场下，界面 SCB 环链也会执行大量的环迁移动力学，从而促进界面滑移。
{"title":"Interfacial Polymer Rheology of Entangled Short-Chain Branched Ring Melts in Shear Flow","authors":"Tae Yong Ha, Seung Heum Jeong, Chunggi Baig","doi":"10.1021/acs.macromol.4c00607","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00607","url":null,"abstract":"We present a detailed analysis of the rheological behavior of entangled short-chain-branched (SCB) ring polymers at interfaces via direct comparison with the corresponding pure (unbranched) ring polymers using atomistic nonequilibrium molecular dynamics simulations of confined polyethylene melt systems under shear flow. To elucidate the general structural and dynamical characteristics of interfacial polymer chains, we analyze various physical properties of the chains in the bulk and interfacial regions separately within the confined systems, such as the chain radius of gyration and its distribution, the average streaming velocity profile, and the degree of interfacial slip, with respect to the applied flow strength. The pure ring polymer melt has a highly extended and aligned chain structure along the flow (<i>x</i>-)direction at the interface, even under weak flow fields, indicative of the strong wall effects via the attractive polymer–wall interactions. In contrast, the interfacial SCB ring chains generally form a compact structure like that of the corresponding bulk chains in the weak flow regime, representing a significant role of the short branches to effectively diminish the wall effect. In conjunction with these structural characteristics, the entangled SCB ring polymer melt displays a markedly smaller degree of interfacial slip than the corresponding pure ring analogue in the weak-to-intermediate flow regimes. Furthermore, while both the pure ring and the SCB ring polymer melt systems reveal similar fundamental molecular mechanisms at the interface with respect to the flow strength (i.e., <i>z</i>-to-<i>x</i> rotation, loop wagging, loop migration, and loop tumbling mechanisms), the SCB ring polymer melt displays relatively weaker loop migration and loop wagging dynamics with highly curvy backbone structures in the intermediate flow regime. In the strong flow regime, both the pure ring and SCB ring systems exhibit the loop tumbling mechanism together with intensive collisions between the interfacial chains and the wall. However, the interfacial SCB ring chains execute substantial loop migration dynamics even at high flow fields, which facilitates interfacial slip.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141425332","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 : 2024-06-18DOI: 10.1021/acs.macromol.4c00230
Zhuangli Cai, Shangchao Lin, Changying Zhao
The Wigner theory for multichannel thermal transport has become a new theoretical paradigm for studying glassy materials like polymers beyond the classic phonon-gas theory. Although thermal transport in bulk polymers can be enhanced by aligning molecular chains, the role of heat carriers in polymers remains obscure. In this work, using the state-of-the-art Wigner theory, diffusions and locons are found to contribute significantly to the total thermal conductivity of disordered and aligned polymers due to coherence between proximate modes. Strikingly, locons contribute remarkably, 43 and 54%, to the total thermal conductivity of disordered and aligned polymers, respectively, due to their high generalized velocities and generalized lifetimes. Interestingly, some locons in aligned polymers form propagative wave packets with ultralong mean free paths (MFPs) and become efficient heat carriers, which is supported by the high spatial extent of locons along their wavevectors. The thermal conductivities of both polymer models increase with temperature due to increased generalized specific heat and agree well with theoretical and experimental data. This work unveils the unique transport behavior of diffusons and locons, providing new avenues for the thermal management of polymer-based electronics packaging and the rational design of organic electronics, optoelectronics, and thermoelectrics.
{"title":"Anomalous Diffuson and Locon-Dominated Wigner Multi-Channel Thermal Transport in Disordered and Shear-Aligned Polymers","authors":"Zhuangli Cai, Shangchao Lin, Changying Zhao","doi":"10.1021/acs.macromol.4c00230","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00230","url":null,"abstract":"The Wigner theory for multichannel thermal transport has become a new theoretical paradigm for studying glassy materials like polymers beyond the classic phonon-gas theory. Although thermal transport in bulk polymers can be enhanced by aligning molecular chains, the role of heat carriers in polymers remains obscure. In this work, using the state-of-the-art Wigner theory, diffusions and locons are found to contribute significantly to the total thermal conductivity of disordered and aligned polymers due to coherence between proximate modes. Strikingly, locons contribute remarkably, 43 and 54%, to the total thermal conductivity of disordered and aligned polymers, respectively, due to their high generalized velocities and generalized lifetimes. Interestingly, some locons in aligned polymers form propagative wave packets with ultralong mean free paths (MFPs) and become efficient heat carriers, which is supported by the high spatial extent of locons along their wavevectors. The thermal conductivities of both polymer models increase with temperature due to increased generalized specific heat and agree well with theoretical and experimental data. This work unveils the unique transport behavior of diffusons and locons, providing new avenues for the thermal management of polymer-based electronics packaging and the rational design of organic electronics, optoelectronics, and thermoelectrics.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141425234","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 : 2024-06-18DOI: 10.1021/acs.macromol.4c00409
Yikai Yin, Shaswat Mohanty, Christopher B. Cooper, Zhenan Bao, Wei Cai
Highly stretchable and self-healable supramolecular elastomers are promising materials for future soft electronics, biomimetic systems, and smart textiles, due to their dynamic cross-linking bonds. The dynamic or reversible nature of the cross-links gives rise to interesting macroscopic responses in these materials such as self-healing and rapid stress-relaxation. However, the relationship between bond activity and macroscopic mechanical response, and the self-healing properties of these dynamic polymer networks (DPNs) remains poorly understood. Using coarse-grained molecular dynamics (CGMD) simulations, we reveal a fundamental connection between the macroscopic behaviors of DPNs and the shortest paths between distant nodes in the polymer network. Notably, the trajectories of the material on the shortest path-strain map provide key insights into understanding the stress–strain hysteresis, anisotropy, stress relaxation, and self-healing of DPNs. Based on CGMD simulations under various loading histories, we formulate a set of empirical rules that dictate how the shortest path interacts with stress and strain. This lays the foundation for the development of a physics-based theory centered around the nonlocal microstructural feature of shortest paths to predict the mechanical behavior of DPNs.
{"title":"Network Evolution Controlling Strain-Induced Damage and Self-Healing of Elastomers with Dynamic Bonds","authors":"Yikai Yin, Shaswat Mohanty, Christopher B. Cooper, Zhenan Bao, Wei Cai","doi":"10.1021/acs.macromol.4c00409","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00409","url":null,"abstract":"Highly stretchable and self-healable supramolecular elastomers are promising materials for future soft electronics, biomimetic systems, and smart textiles, due to their dynamic cross-linking bonds. The dynamic or reversible nature of the cross-links gives rise to interesting macroscopic responses in these materials such as self-healing and rapid stress-relaxation. However, the relationship between bond activity and macroscopic mechanical response, and the self-healing properties of these dynamic polymer networks (DPNs) remains poorly understood. Using coarse-grained molecular dynamics (CGMD) simulations, we reveal a fundamental connection between the macroscopic behaviors of DPNs and the shortest paths between distant nodes in the polymer network. Notably, the trajectories of the material on the shortest path-strain map provide key insights into understanding the stress–strain hysteresis, anisotropy, stress relaxation, and self-healing of DPNs. Based on CGMD simulations under various loading histories, we formulate a set of empirical rules that dictate how the shortest path interacts with stress and strain. This lays the foundation for the development of a physics-based theory centered around the nonlocal microstructural feature of shortest paths to predict the mechanical behavior of DPNs.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141436093","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 : 2024-06-18DOI: 10.1021/acs.macromol.4c00438
Renkuan Cao, Fan Peng, Cui Nie, Yunhan Zhang, Hao Sun, Ziwei Liu, Tingyu Xu, Liangbin Li
The debate surrounding preorders in the primary nucleation of polymer crystals has captivated scientists for decades. By constructing a cylindrical order parameter (COP), we observe a preordering-crystallization two-step nucleation process in a molecular dynamics simulation of polymer crystallization. Instead of the sharp interface between amorphous and crystalline regions assumed by classical nucleation theory (CNT), we observe a gradient COP profile that shifts toward higher COP values as the nucleus size increases. In nucleation dynamics, we depart from the Markov process described in the CNT, where single particles attach to and detach from nuclei without memory. Instead, we find that nucleation occurs through particle fluctuations with a memory effect, which is enhanced as the nucleus size increases, leading to positive feedback. This mechanism of nucleation via particle fluctuations with memory effect fundamentally diverges from CNT and previous nonclassical nucleation models, offering a new perspective on understanding the nucleation of polymers.
{"title":"Primary Nucleation of Polymer Crystal via Particles Fluctuation with Non-Markovian Effect","authors":"Renkuan Cao, Fan Peng, Cui Nie, Yunhan Zhang, Hao Sun, Ziwei Liu, Tingyu Xu, Liangbin Li","doi":"10.1021/acs.macromol.4c00438","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00438","url":null,"abstract":"The debate surrounding preorders in the primary nucleation of polymer crystals has captivated scientists for decades. By constructing a cylindrical order parameter (COP), we observe a preordering-crystallization two-step nucleation process in a molecular dynamics simulation of polymer crystallization. Instead of the sharp interface between amorphous and crystalline regions assumed by classical nucleation theory (CNT), we observe a gradient COP profile that shifts toward higher COP values as the nucleus size increases. In nucleation dynamics, we depart from the Markov process described in the CNT, where single particles attach to and detach from nuclei without memory. Instead, we find that nucleation occurs through particle fluctuations with a memory effect, which is enhanced as the nucleus size increases, leading to positive feedback. This mechanism of nucleation via particle fluctuations with memory effect fundamentally diverges from CNT and previous nonclassical nucleation models, offering a new perspective on understanding the nucleation of polymers.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141425255","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 : 2024-06-18DOI: 10.1021/acs.macromol.4c01168
Ariane Charland-Martin, Graham S. Collier
Understanding the influence of chemical environments on the degradation properties of conjugated polymers is an important task for the continued development of sustainable materials with potential utility in biomedical and optoelectronic applications. Azomethine-containing polymers were synthesized via palladium-catalyzed direct arylation polymerization (DArP) and used to study fundamental degradation trends upon exposure to acid. Shifts in the UV–vis absorbance spectra and the appearance/disappearance of aldehyde and imine diagnostic peaks within the 1H NMR spectra indicate that the polymers will degrade in the presence of acid. After degradation, the aldehyde starting material was recovered in high yields and was shown to maintain structural integrity when compared with commercial starting materials. Solution-degradation studies found that rates of degradation vary from 5 h to 90 s depending on the choice of solvent or acid used for hydrolysis. Additionally, the polymer was shown to degrade in the presence of perfluoroalkyl substances (PFASs), which makes them potentially useful as PFAS-sensitive sensors. Ultimately, this research provides strategies to control the degradation kinetics of azomethine-containing polymers through the manipulation of environmental factors and guides the continued development of azomethine-based materials.
{"title":"Understanding Degradation Dynamics of Azomethine-containing Conjugated Polymers","authors":"Ariane Charland-Martin, Graham S. Collier","doi":"10.1021/acs.macromol.4c01168","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c01168","url":null,"abstract":"Understanding the influence of chemical environments on the degradation properties of conjugated polymers is an important task for the continued development of sustainable materials with potential utility in biomedical and optoelectronic applications. Azomethine-containing polymers were synthesized via palladium-catalyzed direct arylation polymerization (DArP) and used to study fundamental degradation trends upon exposure to acid. Shifts in the UV–vis absorbance spectra and the appearance/disappearance of aldehyde and imine diagnostic peaks within the <sup>1</sup>H NMR spectra indicate that the polymers will degrade in the presence of acid. After degradation, the aldehyde starting material was recovered in high yields and was shown to maintain structural integrity when compared with commercial starting materials. Solution-degradation studies found that rates of degradation vary from 5 h to 90 s depending on the choice of solvent or acid used for hydrolysis. Additionally, the polymer was shown to degrade in the presence of perfluoroalkyl substances (PFASs), which makes them potentially useful as PFAS-sensitive sensors. Ultimately, this research provides strategies to control the degradation kinetics of azomethine-containing polymers through the manipulation of environmental factors and guides the continued development of azomethine-based materials.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141425374","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 : 2024-06-18DOI: 10.1021/acs.macromol.4c00832
Daniel J. MacKinnon, Ben Drain, C. Remzi Becer
The thermoreversible Diels–Alder (DA) reaction provides access to reversible thermosets and thus a pathway to their circular recycling. However, the known thermoreversible diene–dienophile DA pairs are very limited and primarily involve the furan–maleimide pair; hence, there is a need to investigate novel pairs that can provide thermal reversibility in chemical binding at higher and lower temperatures. Hence, a set of 24 diene–dienophile pairs are screened for their tendency to undergo a Diels–Alder (DA) reaction at temperatures up to 140 °C. Of the 21 viable DA pairs, 16 DA pairs then successfully underwent gelation in an analogous polymer cross-linking system. The viability of the thermoreversible retro-Diels–Alder (rDA) reaction at elevated temperatures was then studied via a dissolution study, dynamic scanning calorimetry, and dynamic mechanical analysis. Two novel pairs were shown to undergo rDA degelation for the first time in a polymeric system. [Anthracene-9-methanol + citraconimide] and [anthracene-9-methanol + monomethyl fumarate amide] underwent degelation at 277 and 247 °C, respectively. Several additional novel gels showed dissolution at temperatures up to 250 °C, suggesting that their rDA processes may be accessible, albeit at higher temperatures. The partial self-healing of these two thermoreversible gels at temperatures of 100 and 150 °C, significantly below their degelation temperatures, is also demonstrated.
{"title":"Exploring Polymeric Diene–Dienophile Pairs for Thermoreversible Diels–Alder Reactions","authors":"Daniel J. MacKinnon, Ben Drain, C. Remzi Becer","doi":"10.1021/acs.macromol.4c00832","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00832","url":null,"abstract":"The thermoreversible Diels–Alder (DA) reaction provides access to reversible thermosets and thus a pathway to their circular recycling. However, the known thermoreversible diene–dienophile DA pairs are very limited and primarily involve the furan–maleimide pair; hence, there is a need to investigate novel pairs that can provide thermal reversibility in chemical binding at higher and lower temperatures. Hence, a set of 24 diene–dienophile pairs are screened for their tendency to undergo a Diels–Alder (DA) reaction at temperatures up to 140 °C. Of the 21 viable DA pairs, 16 DA pairs then successfully underwent gelation in an analogous polymer cross-linking system. The viability of the thermoreversible retro-Diels–Alder (rDA) reaction at elevated temperatures was then studied via a dissolution study, dynamic scanning calorimetry, and dynamic mechanical analysis. Two novel pairs were shown to undergo rDA degelation for the first time in a polymeric system. [Anthracene-9-methanol + citraconimide] and [anthracene-9-methanol + monomethyl fumarate amide] underwent degelation at 277 and 247 °C, respectively. Several additional novel gels showed dissolution at temperatures up to 250 °C, suggesting that their rDA processes may be accessible, albeit at higher temperatures. The partial self-healing of these two thermoreversible gels at temperatures of 100 and 150 °C, significantly below their degelation temperatures, is also demonstrated.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141425171","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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