Macromolecules最新文献

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The Extreme of Disentanglement: 100-fold Viscosity Reduction in Model Single-Chain Nanoparticles 解缠的极限:单链纳米粒子模型粘度降低 100 倍
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-13 DOI: 10.1021/acs.macromol.3c02650
Yifu Ruan, Qingzhi Zou, Haoyan Zhang, Yipeng Zhang, Hao Zhang, Weiwei Wu, Hao Liu, Jiajun Yan, GengXin Liu
{"title":"The Extreme of Disentanglement: 100-fold Viscosity Reduction in Model Single-Chain Nanoparticles","authors":"Yifu Ruan, Qingzhi Zou, Haoyan Zhang, Yipeng Zhang, Hao Zhang, Weiwei Wu, Hao Liu, Jiajun Yan, GengXin Liu","doi":"10.1021/acs.macromol.3c02650","DOIUrl":"https://doi.org/10.1021/acs.macromol.3c02650","url":null,"abstract":"The melt rheology of single-chain nanoparticles (SCNPs), which are synthesized by intrachain cross-linking of linear precursors, remains an unresolved issue. In this study, we synthesized linear precursors with different molecular weights (MW) and varying mole percentages of cross-linkers (CrF). The cross-linker, 4-vinylbenzocyclobutene, undergoes thermal-induced coupling. The resulting SCNPs in the melt state exhibited four distinct types of linear viscoelastic behavior: 1) reduced entanglement, 2) viscous-dominant liquids, 3) viscoelastic liquid with an elastic plateau and terminal relaxation, and 4) viscoelastic solid, a persistent elastic plateau with unmeasurable long terminal relaxation times. We observed a nonmonotonic change in viscoelastic behavior as the cross-linking increases. At CrF equal to 4%, Type 1 SCNP is still polymer-like, but the degree of entanglement is reduced. When CrF increased to 8%, the elastic plateau completely disappeared, and the viscous-dominant behavior is similar to the Zimm or Rouse model. Complete disentanglement is achieved even for high MW. In Type 2, the relaxation times and zero-shear viscosities show weaker dependence (a power of 1) on MW compared to linear polymers (a power of 3.4). Thus, the relaxation times and viscosities of such SCNPs can be 100 times smaller than their linear counterparts of the same MW. At even higher CrF, the storage modulus would surpass the loss modulus again if the MW is sufficiently high. This elasticity is due to a mechanism other than entanglements but is analogous to the colloidal domain. Relaxation times or viscosities increase divergently and exceed the experimental measurability in Type 4. The boundary between Types 3 and 4 might be considered as the boundary between polymers and colloids. Using SCNPs as a model system for detailed rheological characterization, we demonstrate the dynamics of the transition from linear polymers to particles. Type 2 SCNPs could be regarded as the extreme of disentanglement, achieved by an appropriate amount of intrachain cross-linking. Such a significant viscosity reduction might support the development of more energy-efficient polymers.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141602838","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}
引用次数: 0
Modulation of π-Conjugation of Polymer Main Chain Containing π-Extended Benzoxaborin by Molecular Addition 通过分子添加调控含π-扩展苯并氧硼烷的聚合物主链的π-共轭作用
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-12 DOI: 10.1021/acs.macromol.4c00799
Shuhei Morimoto, Kazuya Tanimura, Masayuki Gon, Takatoshi Suematsu, Ken Okamoto, Hiroyuki Watanabe, Hideo Taka, Hiroshi Kita, Kazuo Tanaka
{"title":"Modulation of π-Conjugation of Polymer Main Chain Containing π-Extended Benzoxaborin by Molecular Addition","authors":"Shuhei Morimoto, Kazuya Tanimura, Masayuki Gon, Takatoshi Suematsu, Ken Okamoto, Hiroyuki Watanabe, Hideo Taka, Hiroshi Kita, Kazuo Tanaka","doi":"10.1021/acs.macromol.4c00799","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00799","url":null,"abstract":"We synthesize novel cyclic boronic acids incorporated into the main-chain π-conjugated system. The optical measurements under basic conditions reveal that the oligomer binds one-to-one to the sugar containing the <i>cis</i>-1,2-diol structure at the cyclic boronic acid moiety. In particular, the binding is accompanied by a bathochromic shift in absorption and emission spectra. The π-conjugated polymer maintained similar characteristics to the oligomer but showed emission in the longer wavelength region (λ<sub>PL</sub> = 493–525 nm) where the color change was clearly detectable before and after the coordination of diols. Theoretical calculations with density functional theory reveal that the diol bonding to the cyclic boronic acid moiety elevates the energy levels of frontier molecular orbitals, especially the highest occupied molecular orbital. This study demonstrates that the introduction of cyclic boronic acid into π-conjugated polymers is effective for detecting diols with emission color change under mild conditions as well as for manipulating the electronic structures of polymer main chains.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141602841","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}
引用次数: 0
Leveraging Impurities in Macromonomers from Direct-Growth Polymerizations to Produce Supersoft Bottlebrush Networks with Tunable Mechanical Properties 利用直接生长聚合反应产生的大单体中的杂质,生产具有可调机械特性的超软底刷网络
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-12 DOI: 10.1021/acs.macromol.4c01419
Yutong Liu, Henry L. Cater, Anthony J. Arrowood, Gabriel E. Sanoja, Zachariah A. Page
{"title":"Leveraging Impurities in Macromonomers from Direct-Growth Polymerizations to Produce Supersoft Bottlebrush Networks with Tunable Mechanical Properties","authors":"Yutong Liu, Henry L. Cater, Anthony J. Arrowood, Gabriel E. Sanoja, Zachariah A. Page","doi":"10.1021/acs.macromol.4c01419","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c01419","url":null,"abstract":"Bottlebrush polymers are coveted for their supersoft, tissue-like properties. Accordingly, several approaches have emerged to create these materials, yet synthetic challenges remain regarding the number of iterative reactions required to prepare precursors and the cocreation of difficult-to-remove impurities, such as unfunctionalized or bis-functionalized macromonomers (MMs). In this work, we develop a tandem photoiniferter and ring-opening metathesis polymerization method to furnish poly(<i>n</i>-butyl acrylate) bottlebrush polymers and networks without the requirement for MM postfunctionalization or the addition of further cross-linking agents. Systematic optimization of polymerization conditions enabled the preparation of ultrahigh-molecular-weight bottlebrush polymers (∼1000 kDa) with narrow dispersity (∼1.2) along with solvent-free elastomers having moduli akin to those of supersoft biological tissues (∼10 kPa). Mechanical properties of the networks were easily tailored by controlling the conversion of photoiniferter polymerization due to its correlation with the amount of in situ cross-linker formed. This report provides a streamlined approach to generate bottlebrush polymers while simultaneously providing structure–property relationships that will inform their preparation and utility in biomedical applications, such as tissue engineering and adhesives.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141602843","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}
引用次数: 0
Mechanochromic Luminescence of π-Conjugated Polymer Based on Pyridylenolate Boron Complexes: Molecular Design and Application to Shear-Force Memory 基于吡啶烯酸硼配合物的π-共轭聚合物的机械变色发光:剪切力记忆的分子设计与应用
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-12 DOI: 10.1021/acs.macromol.4c01149
Yuto Aoyama, Shunichiro Ito, Kazuo Tanaka
{"title":"Mechanochromic Luminescence of π-Conjugated Polymer Based on Pyridylenolate Boron Complexes: Molecular Design and Application to Shear-Force Memory","authors":"Yuto Aoyama, Shunichiro Ito, Kazuo Tanaka","doi":"10.1021/acs.macromol.4c01149","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c01149","url":null,"abstract":"Mechanochromic luminescent (MCL) materials show emission color changes in response to external force. Although the development of MCL conjugated polymers is one of the hot topics because of their wide applicability for fabricating film-type mechanical and pressure sensors, it is still challenging to observe MCL behaviors from single-component polymer films. Herein, we report the MCL properties of the conjugated polymer consisting of boron pyridylenolate in film and its mechanism. We prepared copolymers involving pyridylenolate complexes bearing difluoride and diphenyl groups on boron and investigated their optical properties. Consequently, we found that the fluorine-substituted complex and especially its conjugated polymer showed clear MCL. From the mechanistic studies, we concluded that the degree of intermolecular interactions should play a key role in MCL behaviors. The boron complex units in the polymer main chain can detect microenvironmental changes in polymer morphology as luminescent color changes caused by the mechanical treatments owing to high environmental sensitivity. Finally, based on the sensitive MCL behaviors of the polymer, it was demonstrated that the polymer film was able to work as a shear-force memory at the tiny spot for needle puncture marks.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141602842","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}
引用次数: 0
Stearic Acid-Infused PDMS PolyMIPEs Exhibiting Shape Memory Behavior 注入硬脂酸的 PDMS 聚甲基丙烯酸酯具有形状记忆特性
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-12 DOI: 10.1021/acs.macromol.4c00457
Anthony Smith, Anna Brown, Jack Newman, Neil Ayres
{"title":"Stearic Acid-Infused PDMS PolyMIPEs Exhibiting Shape Memory Behavior","authors":"Anthony Smith, Anna Brown, Jack Newman, Neil Ayres","doi":"10.1021/acs.macromol.4c00457","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00457","url":null,"abstract":"Emulsion-templated polymerizations are an attractive route to prepare porous materials that possess broad tunability by controlling the features of the emulsion template. Emulsion-templated polymer materials possessing shape memory behavior have also been reported, usually using (meth)acrylate monomers. However, achieving shape memory properties in emulsion-templated materials with polymers that do not possess accessible thermal transitions, including polydimethylsiloxane (PDMS), remains challenging. Here, porous PDMS materials have been prepared with stearic acid within the continuous phase of the emulsion template. The inclusion of stearic acid imparts the material with a transition temperature of ∼70 °C, and the porous materials in this work obtained fixity &gt;90% and recovery &gt;95% over multiple shape memory cycles. These results demonstrate how low glass-transition temperature emulsion-templated polymer materials can easily be given shape memory properties. This work should be a starting point for studies of elastomeric emulsion-templated polymer materials in applications, including in soft robotics.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141602837","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}
引用次数: 0
Radical Polymerization of Vinyl Boronate Involving Backbiting Chain Transfer and Postpolymerization Oxidation Affording Branched Poly(vinyl alcohol)s 涉及背向链转移和聚合后氧化的乙烯基硼酸酯的自由基聚合,生成支链聚乙烯醇
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-12 DOI: 10.1021/acs.macromol.4c00744
Tomoaki Kanazawa, Tsuyoshi Nishikawa, Makoto Ouchi
{"title":"Radical Polymerization of Vinyl Boronate Involving Backbiting Chain Transfer and Postpolymerization Oxidation Affording Branched Poly(vinyl alcohol)s","authors":"Tomoaki Kanazawa, Tsuyoshi Nishikawa, Makoto Ouchi","doi":"10.1021/acs.macromol.4c00744","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00744","url":null,"abstract":"We found that radical polymerization of vinyl boronic acid pinacol ester (VBpin) was accompanied by a backbiting chain transfer reaction to the polymer backbone, and thus, branched chains were generated via the propagation from the midchain radical. The subsequent oxidation for the boron pendant afforded a branched poly(vinyl alcohol) (PVA), which was certainly supported by NMR structural analyses. The synthesis of the branched PVA is inaccessible via radical polymerization of vinyl acetate (VAc) and subsequent saponification because the VAc polymerization favors the chain transfer reaction to pendant methyl groups over that to the backbone. Our effort was also directed to tuning the branch degree via copolymerization of VBpin with VAc for studies on effects of the branch degree on the physical properties, such as solubility in water and crystallization in the bulk state.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141602839","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}
引用次数: 0
Regulating the Chirality of the Superhelices Self-Assembled from Block Copolymer/Homopolymer Binary Systems by the Mixing Ratio of the Polymers 通过聚合物的混合比例调节嵌段共聚物/均聚物二元体系自组装超螺旋的手性
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-11 DOI: 10.1021/acs.macromol.4c00474
Kexin Cao, Yue Du, Jiaping Lin, Chunhua Cai
{"title":"Regulating the Chirality of the Superhelices Self-Assembled from Block Copolymer/Homopolymer Binary Systems by the Mixing Ratio of the Polymers","authors":"Kexin Cao, Yue Du, Jiaping Lin, Chunhua Cai","doi":"10.1021/acs.macromol.4c00474","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00474","url":null,"abstract":"Chirality control is one of the fundamental aspects of the research of chiral nanostructures. Currently, there are a few reports regarding the chirality variation of polymer nanostructures induced by ambient preparation conditions without changing the chiral sense of the polymer backbones. Herein, we report findings that the chirality of the superhelices self-assembled by a binary polymer system containing rodlike core-forming poly(γ-benzyl-<span>l</span>-glutamate) (PBLG) homopolymers and helical screw-forming poly(γ-benzyl-<span>l</span>-glutamate)-<i>block</i>-poly(ethylene glycol) (PBLG-<i>b</i>-PEG) block copolymers can be varied by the mixture ratio of the polymers. It was found that the chirality of the PBLG-<i>b</i>-PEG/PBLG superhelices can change from right-handed to left-handed by decreasing the fraction of the block copolymers. In such a process, the PBLG backbone of polymers retains their right-handed helical conformation, while the arrangement of the pendant phenyl groups varies from a contracted left-handed form to an extended right-handed form, which leads to the chirality evolution behaviors of the superhelices. This work presents a novel route regulating the chirality of chiral nanostructures formed by chiral polymers and enriches our knowledge for chirality evolution behaviors from polymers to nanostructures.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141588734","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}
引用次数: 0
Multicomponent Polymerization of Sulfur, Diynes, and Aromatic Diamines and Facile Tuning of Polymer Backbone Structures 硫、二炔和芳香族二胺的多组分聚合以及聚合物骨架结构的便捷调节
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-11 DOI: 10.1021/acs.macromol.4c00879
Yuzhang Huang, Rongrong Hu, Ben Zhong Tang
{"title":"Multicomponent Polymerization of Sulfur, Diynes, and Aromatic Diamines and Facile Tuning of Polymer Backbone Structures","authors":"Yuzhang Huang, Rongrong Hu, Ben Zhong Tang","doi":"10.1021/acs.macromol.4c00879","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00879","url":null,"abstract":"Polythioamides have attracted growing research interests owing to their structural similarity to extensively applied high-performance polyamide analogues, together with the additional properties endowed by sulfur such as strong metal coordination ability, high light refractivity, and unique photophysical properties. The synthesis of polythioamides, especially aromatic polythioamides, remained challenging due to the poor reactivity of aromatic amine monomers. In this work, through activation of sulfur by KF, a multicomponent polymerization (MCP) of elemental sulfur, aromatic diynes, and aromatic diamines was developed in the presence of KF in DMSO at 100 °C, affording aromatic polythioamides in high yields. Small molecular model reaction study suggested that under the reaction conditions, terminal alkyne could react with sulfur and aromatic amine to afford both thioamide and thiourea, depending on the loading ratio of alkyne and amine. With these competitive polymerization pathways, the backbone structures of the MCP product could be facilely tuned by simply changing the monomer loading ratio of diynes and diamines, producing random poly(thioamide-thiourea)s with decent molecular weights (<i>M</i><sub><i>n</i></sub>s) of up to 19,200 g/mol in high yields of up to 98%. Through the polymer backbone structural tuning, the polymer thermal properties, including decomposition temperatures and glass transition temperatures, could be adjusted. The MCP has hence demonstrated facile synthesis of polythioamides and simple tuning of the backbone structure and property of sulfur-containing polymer materials.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141602845","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}
引用次数: 0
Ring-Opening Polymerization of α-Diazo Lactones: Access to Diazo-Containing Polyesters and Their Post-Polymerization Modifications α-重氮内酯的开环聚合:获得含重氮的聚酯及其聚合后改性
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-11 DOI: 10.1021/acs.macromol.4c00750
Lefei Yu, Yisong Wang, Qi Zhou, Xiaotong Wu, Zhenning Yu, Yan Xu, Zi-Chen Li, Jianbo Wang
{"title":"Ring-Opening Polymerization of α-Diazo Lactones: Access to Diazo-Containing Polyesters and Their Post-Polymerization Modifications","authors":"Lefei Yu, Yisong Wang, Qi Zhou, Xiaotong Wu, Zhenning Yu, Yan Xu, Zi-Chen Li, Jianbo Wang","doi":"10.1021/acs.macromol.4c00750","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00750","url":null,"abstract":"The properties of polyesters can be enhanced by the introduction of various functional groups, while transformations of a diazo group via a carbene intermediate provide efficient approaches for functional group introduction. We herein report the first ring-opening polymerization (ROP) of 5, 6, and 7-membered α-diazo lactones using <i>t</i>-BuOK as the initiator. The diazo groups can be well tolerated in the polymerization condition, leading to stable, diazo-containing polyesters that can be readily isolated and characterized. Post-polymerization transformations of the diazo groups, including [1,2]-hydrogen migration, Si–H insertions, and S–H insertions, further provide polyesters that are nontrivial to access. Further, the introduction of diazo groups generally increases the ring strain of lactones and alters their polymerizability, which is more pronounced for α-diazo γ-butyrolactone. The ROP of α-diazo δ-valerolactone generates a new type of diazo-containing polyesters that can be depolymerized upon heating.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141588741","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}
引用次数: 0
Thermal Conductivity of Polyurethane Thin Films 聚氨酯薄膜的导热性
IF 5.5 1区 化学
Macromolecules Pub Date : 2024-07-11 DOI: 10.1021/acs.macromol.4c00401
Jingyi Zhou, Xiaoru Li, Chen Chen, Weijun Zhou, Thomas R. Fielitz, Paul V. Braun, David G. Cahill
{"title":"Thermal Conductivity of Polyurethane Thin Films","authors":"Jingyi Zhou, Xiaoru Li, Chen Chen, Weijun Zhou, Thomas R. Fielitz, Paul V. Braun, David G. Cahill","doi":"10.1021/acs.macromol.4c00401","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00401","url":null,"abstract":"Heat transport by solid conduction of polyurethane (PU) is a significant fraction of the total thermal conductivity of rigid PU foam. Despite its significance, the intrinsic thermal conductivity of solid PU materials is not well characterized, a circumstance largely attributable to the challenges of preparing fully dense materials that are free of voids due to CO<sub>2</sub> gas formation and entrapment caused by the fast reaction between a trace amount of water in a polyol and isocyanate during curing. We developed a protocol to prepare dense homogeneous PU thin films with thicknesses on the order of 100 nm, prepared eight formulations of PU films from a series of polyols and isocyanates with different functionalities, and measured their thermal conductivity, heat capacity, longitudinal speed of sound, and density by time-domain thermoreflectance, picosecond acoustics, and Rutherford backscattering spectrometry, respectively. The thermal conductivity of these PU materials spans a narrow range of 0.19 ± 0.03 W/(m K). The glass transition temperature of polymer thin films as thin as 100 nm was measured based on a photothermal displacement method. We used data for the longitudinal speed of sound and atomic density to predict the thermal conductivity using the minimum thermal conductivity model (MTCM). While the MTCM agrees with the measured thermal conductivity to within 30%, the variations in the thermal conductivity that we observe experimentally cannot be explained by the small variations in sound velocity and density. Our findings provide new insights into thermal conduction properties of PU solids in rigid PU foam and provide a fundamental basis for the construction of models of the thermal performance and the development of better insulation materials.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141602844","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}
引用次数: 0
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