The crystal structures of iodine complexes of nylon-6 and nylon-66 samples were proposed on the basis of 2-dimensional wide-angle X-ray diffraction data analysis combined with the observed polarized Raman spectral data and the density functional theoretical calculations. As reported in our previous paper (Macromolecules, 2024, 57, 2260), the skeletal chains of nylon were found to be contracted about 5% from the fully extended conformations, which are caused by the trans-to-skew torsional angle change around CH2–amide bonds so that the charge transfer occurs from the iodine ion to N–H group. The iodine ion rods are sandwiched between the nylon chains alternately. The I5– and I3– ion rods are oriented, respectively, along the nylon chain axis and in the direction approximately perpendicular to the chain axis. The sandwich packing structure is different among complex I and complex II, which are formed by immersing nylon-6 sample in the iodine solution of different concentration (0.5 and 3 M, respectively). The similar structure model was proposed also for nylon-66. The thus-constructed crystal structure models reproduced the observed X-ray diffraction patterns quite well. By a comparison of the X-ray diffraction data observed for the doubly oriented samples, the geometrical relation was revealed between the pristine nylon crystal and the nylon–iodine complexes.
在二维广角 X 射线衍射数据分析的基础上，结合观察到的偏振拉曼光谱数据和密度泛函理论计算，提出了尼龙-6 和尼龙-66 样品碘配合物的晶体结构。正如我们之前的论文（Macromolecules, 2024, 57, 2260）所述，发现尼龙的骨架链从完全延伸构象收缩了约 5%，这是由于 CH2- 酰胺键周围的反斜角变化导致电荷从碘离子转移到 N-H 基团。碘离子棒交替夹在尼龙链之间。I5- 离子棒和 I3- 离子棒分别沿尼龙链轴线和近似垂直于链轴线的方向排列。将尼龙-6 样品浸入不同浓度（分别为 0.5 和 3 M）的碘溶液中形成的络合物 I 和络合物 II 的夹层堆积结构各不相同。对尼龙-66 也提出了类似的结构模型。由此构建的晶体结构模型很好地再现了观察到的 X 射线衍射图样。通过比较双取向样品的 X 射线衍射数据，可以发现原始尼龙晶体与尼龙-碘络合物之间的几何关系。
{"title":"Crystal Structures of Nylon–Iodine Complexes","authors":"Kohji Tashiro, Marina Gakhutishvili, Tomohiko Takahama","doi":"10.1021/acs.macromol.4c01122","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c01122","url":null,"abstract":"The crystal structures of iodine complexes of nylon-6 and nylon-66 samples were proposed on the basis of 2-dimensional wide-angle X-ray diffraction data analysis combined with the observed polarized Raman spectral data and the density functional theoretical calculations. As reported in our previous paper (<i>Macromolecules</i>, <b>2024</b>, <i>57</i>, 2260), the skeletal chains of nylon were found to be contracted about 5% from the fully extended conformations, which are caused by the trans-to-skew torsional angle change around CH<sub>2</sub>–amide bonds so that the charge transfer occurs from the iodine ion to N–H group. The iodine ion rods are sandwiched between the nylon chains alternately. The I<sub>5</sub><sup>–</sup> and I<sub>3</sub><sup>–</sup> ion rods are oriented, respectively, along the nylon chain axis and in the direction approximately perpendicular to the chain axis. The sandwich packing structure is different among complex I and complex II, which are formed by immersing nylon-6 sample in the iodine solution of different concentration (0.5 and 3 M, respectively). The similar structure model was proposed also for nylon-66. The thus-constructed crystal structure models reproduced the observed X-ray diffraction patterns quite well. By a comparison of the X-ray diffraction data observed for the doubly oriented samples, the geometrical relation was revealed between the pristine nylon crystal and the nylon–iodine complexes.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141489647","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 : 2024-06-29DOI: 10.1021/acs.macromol.4c00539
Chen Chen, Baicheng Mei, Jingyi Zhou, Kenneth S. Schweizer, Christopher M. Evans, Paul V. Braun
Polymer networks are important constituents of ion separation membranes and battery electrolytes. In such systems, understanding the coupling of the network structure to ion transport is important to guide network design. However, a comprehensive understanding of how polymer network variations affect segmental relaxation and ion transport is still lacking. A series of single-anion-conducting polymer networks was synthesized with a controlled crosslinking density, ethylene oxide (EO) side chain length, tethered cationic monomer concentration, and mobile counteranion size. From dielectric spectroscopy, segmental relaxation times were obtained and found to vary by orders of magnitude across the investigated crosslinking densities and side chain lengths. Ionic conductivity is found to be coupled with segmental relaxation, which slowed with an increase in the number of crosslinks, whereas Young’s moduli of the networks are found to be most coupled with the crosslinking density. Longer side chains provide faster segmental relaxation but do not impede the mechanical strength generated by crosslinks, showing an approach toward designing networks with both high moduli and ionic conductivities. Using a similar network with added lithium salts, Li+ transport selectivity is enhanced by weak interactions between Li+ and large anions, as well as higher crosslinking densities.
{"title":"Coupling of Ethylene-Oxide-Based Polymeric Network Structure and Counterion Chemistry to Ionic Conductivity and Ion Selectivity","authors":"Chen Chen, Baicheng Mei, Jingyi Zhou, Kenneth S. Schweizer, Christopher M. Evans, Paul V. Braun","doi":"10.1021/acs.macromol.4c00539","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00539","url":null,"abstract":"Polymer networks are important constituents of ion separation membranes and battery electrolytes. In such systems, understanding the coupling of the network structure to ion transport is important to guide network design. However, a comprehensive understanding of how polymer network variations affect segmental relaxation and ion transport is still lacking. A series of single-anion-conducting polymer networks was synthesized with a controlled crosslinking density, ethylene oxide (EO) side chain length, tethered cationic monomer concentration, and mobile counteranion size. From dielectric spectroscopy, segmental relaxation times were obtained and found to vary by orders of magnitude across the investigated crosslinking densities and side chain lengths. Ionic conductivity is found to be coupled with segmental relaxation, which slowed with an increase in the number of crosslinks, whereas Young’s moduli of the networks are found to be most coupled with the crosslinking density. Longer side chains provide faster segmental relaxation but do not impede the mechanical strength generated by crosslinks, showing an approach toward designing networks with both high moduli and ionic conductivities. Using a similar network with added lithium salts, Li<sup>+</sup> transport selectivity is enhanced by weak interactions between Li<sup>+</sup> and large anions, as well as higher crosslinking densities.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141464096","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 : 2024-06-29DOI: 10.1021/acs.macromol.4c00868
Junkun Pan, Aaron P. Charnay, Michael D. Fayer
Ultrafast infrared (IR) spectroscopy was used to characterize the free volume element (FVE) radius probability distributions (RPDs) of poly(ether imide) (PEI) alumina nanocomposites. The nanocomposites (0–2 wt %) were prepared with 20 nm diameter spherical Al2O3 nanofillers and a small amount of phenyl selenocyanate (PhSeCN) as IR vibrational probes. Restricted orientation anisotropy method (ROAM), an ultrafast IR technique, was used to measure FVE radii. The results yield RPDs as a function of the nanoparticle concentration. The RPDs were decomposed into bulk PEI and interphase region contributions. The ROAM results demonstrate that the polymer chain packing in PEI nanocomposites is significantly altered from that of pure PEI. The average FVE radius increases with increasing nanofiller content. The RPDs indicate that subensembles with smaller radii are disproportionately affected by the presence of the Al2O3 nanofillers, causing the width of the distribution to narrow. The FVE RPDs for the interface regions reveal a distribution with an average radius ∼0.2 Å larger but significantly narrower than the pure PEI distribution. Finally, the interface volume fraction for each nanocomposite sample was determined from the differences in the RPD curves, and the effective interfacial layer thickness was found to be 19.2 ± 0.5 nm. The results demonstrated that FVE characteristics are strongly affected by the proximity to nanoparticles. The nature of the FVEs in the interfacial regions provides information about the microscopic origin of the polymer nanocomposite material’s properties.
{"title":"Poly(ether imide) Alumina Nanocomposites: Interphase Properties Determined from Free Volume Element Radius Distributions","authors":"Junkun Pan, Aaron P. Charnay, Michael D. Fayer","doi":"10.1021/acs.macromol.4c00868","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00868","url":null,"abstract":"Ultrafast infrared (IR) spectroscopy was used to characterize the free volume element (FVE) radius probability distributions (RPDs) of poly(ether imide) (PEI) alumina nanocomposites. The nanocomposites (0–2 wt %) were prepared with 20 nm diameter spherical Al<sub>2</sub>O<sub>3</sub> nanofillers and a small amount of phenyl selenocyanate (PhSeCN) as IR vibrational probes. Restricted orientation anisotropy method (ROAM), an ultrafast IR technique, was used to measure FVE radii. The results yield RPDs as a function of the nanoparticle concentration. The RPDs were decomposed into bulk PEI and interphase region contributions. The ROAM results demonstrate that the polymer chain packing in PEI nanocomposites is significantly altered from that of pure PEI. The average FVE radius increases with increasing nanofiller content. The RPDs indicate that subensembles with smaller radii are disproportionately affected by the presence of the Al<sub>2</sub>O<sub>3</sub> nanofillers, causing the width of the distribution to narrow. The FVE RPDs for the interface regions reveal a distribution with an average radius ∼0.2 Å larger but significantly narrower than the pure PEI distribution. Finally, the interface volume fraction for each nanocomposite sample was determined from the differences in the RPD curves, and the effective interfacial layer thickness was found to be 19.2 ± 0.5 nm. The results demonstrated that FVE characteristics are strongly affected by the proximity to nanoparticles. The nature of the FVEs in the interfacial regions provides information about the microscopic origin of the polymer nanocomposite material’s properties.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141464006","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 : 2024-06-28DOI: 10.1021/acs.macromol.4c00854
Aria C. Zhang, Kohji Ohno, Russell J. Composto
This study investigates the interplay between film thickness and the surface and internal morphologies in polymer nanocomposite (PNC) films. The PNC is 25 wt % poly(methyl methacrylate)-grafted silica nanoparticles (NPs) in poly(styrene-ran-acrylonitrile) annealed in the two-phase region. At greatest confinement (120 nm), NP surface density remains constant, and lateral phase separation is inhibited upon annealing. For thicker films (240–1400 nm), surface density increases with time before approaching ca. 740 NP/μm2, consistent with 2D random close packing. Moreover, lateral domain growth exhibits a dimensional crossover as thickness increases from t1/2 to t1/3, consistent with domain coalescence. Water contact angles decrease upon annealing in agreement with the lateral domain composition. For thickest films (1400–4000 nm), a morphology map summarizes the distinct internal arrangements of NPs: disordered aggregates, continuous vertical pillars, discrete vertical pillars, isolated domains, and random networks. This study of PNC films provides guidance for controlling surface and bulk structure which can lead to improved barrier, mechanical, and transport properties.
{"title":"Film Thickness Dependence of Surface and Internal Morphology Evolution in Polymer-Grafted Nanocomposites","authors":"Aria C. Zhang, Kohji Ohno, Russell J. Composto","doi":"10.1021/acs.macromol.4c00854","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00854","url":null,"abstract":"This study investigates the interplay between film thickness and the surface and internal morphologies in polymer nanocomposite (PNC) films. The PNC is 25 wt % poly(methyl methacrylate)-grafted silica nanoparticles (NPs) in poly(styrene-<i>ran</i>-acrylonitrile) annealed in the two-phase region. At greatest confinement (120 nm), NP surface density remains constant, and lateral phase separation is inhibited upon annealing. For thicker films (240–1400 nm), surface density increases with time before approaching ca. 740 NP/μm<sup>2</sup>, consistent with 2D random close packing. Moreover, lateral domain growth exhibits a dimensional crossover as thickness increases from <i>t</i><sup>1/2</sup> to <i>t</i><sup>1/3</sup>, consistent with domain coalescence. Water contact angles decrease upon annealing in agreement with the lateral domain composition. For thickest films (1400–4000 nm), a morphology map summarizes the distinct internal arrangements of NPs: disordered aggregates, continuous vertical pillars, discrete vertical pillars, isolated domains, and random networks. This study of PNC films provides guidance for controlling surface and bulk structure which can lead to improved barrier, mechanical, and transport properties.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141463762","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 : 2024-06-28DOI: 10.1021/acs.macromol.4c00897
Xuhong Chen, Daniel Rossi, Yinzhong Guo, Qichun Grace Wan, Xiaoyun Chen, Carol E. Mohler, Tzu-Chi Kuo, Zhan Chen
Two-component polyurethane (PU) adhesives possess robust bulk strength and excellent resistance to environmental factors, making them versatile for various applications in construction, transportation, and flexible packaging. However, their adhesion to nonpolar polymers can be suboptimal, potentially limiting their utility. To address this challenge, corona treatment has been employed to enhance the adhesion between nonpolar polymers and PU adhesives. Despite their extensive use, the specific mechanisms behind the adhesion improvement of the two-component PU adhesives on polymer surfaces due to corona treatment remain insufficiently explored at the molecular level, primarily because adhesion involves buried interfaces that are challenging to examine in situ. This study employs sum frequency generation (SFG) vibrational spectroscopy for in situ, nondestructive analysis of the buried interfaces between PU and polypropylene (PP, as a model for nonpolar polymers). Complementary analytical techniques, including Fourier transform infrared (FTIR) spectroscopy and adhesion testing, were also utilized. We conducted time-dependent SFG experiments to observe the molecular interactions at buried interfaces between the PU adhesive and PP during curing. Our findings reveal a significant correlation between adhesion enhancement and the environmental humidity level following corona treatment. Surprisingly, increased adhesion was not observed at low humidity levels (10–15% relative humidity at room temperature), challenging the conventional understanding of the corona treatment effect on adhesion enhancement. SFG measurements indicated that the formation of urea bonds at the PU/PP interface is a key factor in the increase in adhesion strength. This research clarifies the molecular mechanisms by which corona treatment enhances the adhesion of two-component PU adhesives on nonpolar polymer substrates.
{"title":"Effect of Corona Treatment on the Adhesion between a Two-Component Polyurethane Adhesive and Polypropylene","authors":"Xuhong Chen, Daniel Rossi, Yinzhong Guo, Qichun Grace Wan, Xiaoyun Chen, Carol E. Mohler, Tzu-Chi Kuo, Zhan Chen","doi":"10.1021/acs.macromol.4c00897","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00897","url":null,"abstract":"Two-component polyurethane (PU) adhesives possess robust bulk strength and excellent resistance to environmental factors, making them versatile for various applications in construction, transportation, and flexible packaging. However, their adhesion to nonpolar polymers can be suboptimal, potentially limiting their utility. To address this challenge, corona treatment has been employed to enhance the adhesion between nonpolar polymers and PU adhesives. Despite their extensive use, the specific mechanisms behind the adhesion improvement of the two-component PU adhesives on polymer surfaces due to corona treatment remain insufficiently explored at the molecular level, primarily because adhesion involves buried interfaces that are challenging to examine in situ. This study employs sum frequency generation (SFG) vibrational spectroscopy for in situ, nondestructive analysis of the buried interfaces between PU and polypropylene (PP, as a model for nonpolar polymers). Complementary analytical techniques, including Fourier transform infrared (FTIR) spectroscopy and adhesion testing, were also utilized. We conducted time-dependent SFG experiments to observe the molecular interactions at buried interfaces between the PU adhesive and PP during curing. Our findings reveal a significant correlation between adhesion enhancement and the environmental humidity level following corona treatment. Surprisingly, increased adhesion was not observed at low humidity levels (10–15% relative humidity at room temperature), challenging the conventional understanding of the corona treatment effect on adhesion enhancement. SFG measurements indicated that the formation of urea bonds at the PU/PP interface is a key factor in the increase in adhesion strength. This research clarifies the molecular mechanisms by which corona treatment enhances the adhesion of two-component PU adhesives on nonpolar polymer substrates.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141464070","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 : 2024-06-28DOI: 10.1021/acs.macromol.4c00162
Naisheng Jiang, Tianyi Yu, Meng Zhang, Bailee N. Barrett, Haofeng Sun, Jun Wang, Ying Luo, Garrett L. Sternhagen, Sunting Xuan, Guangcui Yuan, Elizabeth G. Kelley, Shuo Qian, Peter V. Bonnesen, Kunlun Hong, Dongcui Li, Donghui Zhang
We investigated the temperature-dependent structural evolution of thermoreversible triblock terpolypeptoid hydrogels, namely poly(N-allyl glycine)-b-poly(N-methyl glycine)-b-poly(N-decyl glycine) (AMD), using small-angle neutron scattering (SANS) with contrast matching in conjunction with X-ray scattering and cryogenic transmission electron microscopy (cryo-TEM) techniques. At room temperature, A100M101D10 triblock terpolypeptoids self-assemble into core–corona-type spherical micelles in aqueous solution. Upon heating above the critical gelation temperature (Tgel), SANS analysis revealed the formation of a two-compartment hydrogel network comprising distinct micellar cores composed of dehydrated A blocks and hydrophobic D blocks. At T ≳ Tgel, the temperature-dependent dehydration of A block further leads to the gradual rearrangement of both A and D domains, forming well-ordered micellar network at higher temperatures. For AMD polymers with either longer D block or shorter A block, such as A101M111D21 and A43M92D9, elongated nonspherical micelles with a crystalline D core were observed at T < Tgel. Although these enlarged crystalline micelles still undergo a sharp sol-to-gel transition upon heating, the higher aggregation number of chains results in the immediate association of the micelles into ordered aggregates at the initial stage, followed by a disruption of the spatial ordering as the temperature further increases. On the other hand, fiber-like structures were also observed for AMD with longer A block, such as A153M127D10, due to the crystallization of A domains. This also influences the assembly pathway of the two-compartment network. Our findings emphasize the critical impact of initial micellar morphology on the structural evolution of AMD hydrogels during the sol-to-gel transition, providing valuable insights for the rational design of thermoresponsive hydrogels with tunable network structures at the nanometer scale.
我们利用小角中子散射（SANS）对比匹配技术，结合 X 射线散射和低温透射电子显微镜（cryo-TEM）技术，研究了热可逆三嵌段三聚肽水凝胶（即聚（N-烯丙基甘氨酸）-b-聚（N-甲基甘氨酸）-b-聚（N-癸基甘氨酸）（AMD）随温度变化的结构演化。室温下，A100M101D10 三嵌段三聚肽在水溶液中自组装成核电晕型球形胶束。加热到临界凝胶化温度（Tgel）以上时，SANS 分析显示形成了由脱水的 A 嵌段和疏水的 D 嵌段组成的独特胶束核心的两室水凝胶网络。在 T ≳ Tgel 温度下，随温度变化的 A 嵌段脱水进一步导致 A 和 D 结构域逐渐重新排列，从而在较高温度下形成有序的胶束网络。对于具有较长 D 嵌段或较短 A 嵌段的 AMD 聚合物（如 A101M111D21 和 A43M92D9），在 T < Tgel 温度下可观察到具有结晶 D 核心的拉长非球形胶束。虽然这些增大的结晶胶束在加热时仍会发生从溶胶到凝胶的急剧转变，但较高的链聚集数导致胶束在初始阶段立即结合成有序的聚集体，随后随着温度的进一步升高，空间有序性被破坏。另一方面，由于 A 结构域的结晶，A153M127D10 等具有较长 A 嵌段的 AMD 也出现了纤维状结构。这也影响了两室网络的组装途径。我们的研究结果强调了在溶胶到凝胶的转变过程中，初始胶束形态对 AMD 水凝胶结构演变的关键影响，为合理设计具有纳米级可调网络结构的热致伸缩性水凝胶提供了宝贵的见解。
{"title":"Effect of Micellar Morphology on the Temperature-Induced Structural Evolution of ABC Polypeptoid Triblock Terpolymers into Two-Compartment Hydrogel Network","authors":"Naisheng Jiang, Tianyi Yu, Meng Zhang, Bailee N. Barrett, Haofeng Sun, Jun Wang, Ying Luo, Garrett L. Sternhagen, Sunting Xuan, Guangcui Yuan, Elizabeth G. Kelley, Shuo Qian, Peter V. Bonnesen, Kunlun Hong, Dongcui Li, Donghui Zhang","doi":"10.1021/acs.macromol.4c00162","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00162","url":null,"abstract":"We investigated the temperature-dependent structural evolution of thermoreversible triblock terpolypeptoid hydrogels, namely poly(<i>N</i>-allyl glycine)-<i>b</i>-poly(<i>N</i>-methyl glycine)-<i>b</i>-poly(<i>N</i>-decyl glycine) (AMD), using small-angle neutron scattering (SANS) with contrast matching in conjunction with X-ray scattering and cryogenic transmission electron microscopy (cryo-TEM) techniques. At room temperature, A<sub>100</sub>M<sub>101</sub>D<sub>10</sub> triblock terpolypeptoids self-assemble into core–corona-type spherical micelles in aqueous solution. Upon heating above the critical gelation temperature (<i>T</i><sub>gel</sub>), SANS analysis revealed the formation of a two-compartment hydrogel network comprising distinct micellar cores composed of dehydrated A blocks and hydrophobic D blocks. At <i>T</i> ≳ <i>T</i><sub>gel</sub>, the temperature-dependent dehydration of A block further leads to the gradual rearrangement of both A and D domains, forming well-ordered micellar network at higher temperatures. For AMD polymers with either longer D block or shorter A block, such as A<sub>101</sub>M<sub>111</sub>D<sub>21</sub> and A<sub>43</sub>M<sub>92</sub>D<sub>9</sub>, elongated nonspherical micelles with a crystalline D core were observed at <i>T</i> < <i>T</i><sub>gel</sub>. Although these enlarged crystalline micelles still undergo a sharp sol-to-gel transition upon heating, the higher aggregation number of chains results in the immediate association of the micelles into ordered aggregates at the initial stage, followed by a disruption of the spatial ordering as the temperature further increases. On the other hand, fiber-like structures were also observed for AMD with longer A block, such as A<sub>153</sub>M<sub>127</sub>D<sub>10</sub>, due to the crystallization of A domains. This also influences the assembly pathway of the two-compartment network. Our findings emphasize the critical impact of initial micellar morphology on the structural evolution of AMD hydrogels during the sol-to-gel transition, providing valuable insights for the rational design of thermoresponsive hydrogels with tunable network structures at the nanometer scale.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141463737","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 : 2024-06-28DOI: 10.1021/acs.macromol.4c00625
Subeen Kim, Jeremy L. Swartz, Oliver Sala, Molly Sun, Alexander K. Oanta, Jacob P. Brutman, Alaaeddin Alsbaiee, William R. Dichtel
Carbamate formation and exchange catalysts enable efficient polyurethane (PU) manufacturing, as well as emerging recycling and reprocessing methods for PU thermosets. Zirconium β-diketonate complexes, such as Zr acetylacetonate [Zr(acac)4], are effective alternatives to toxic organotin catalysts that have been used for PU reprocessing. Here, we report that Zr(acac)4 undergoes a thermally activated process in the PU network during reprocessing that transforms it into a more active carbamate exchange catalyst. This process is associated with the irreversible loss of acetylacetonate ligands and is not observed for the more sterically hindered Zr 2,2,6,6-tetramethyl-3,5-heptanedione [Zr(tmhd)4] complex. Crossover experiments between PU thermoplastics indicated enhanced carbamate exchange after the thermal activation of Zr(acac)4 in the presence of one of the PUs, whereas a sample of Zr(acac)4 activated in the absence of the PU had no catalytic activity. Thermal gravimetric analysis suggested that this process is associated with the loss of one protonated acac ligand. Stress relaxation analysis of PU thermosets indicated a distinct change in the characteristic relaxation time associated with the thermal activation of Zr(acac)4 at temperatures above 140 °C; no such change was observed for samples reprocessed using Zr(tmhd)4. Density functional theory and molecular experiments suggest that irreversible ligand exchange of acac with alkoxide or carbamate reduces the activation energy for urethane formation and reversion. Furthermore, the Zr(acac)4 catalyst activated in the presence of a PU’s polyol precursor provided more porous and less dense PU foams compared to those made using the unactivated Zr(acac)4 catalyst. These findings are important for developing improved PU synthesis and recycling processes. Thermally activating a catalyst during reprocessing may provide more nuanced control of the in-use and reprocessing characteristics of PU thermosets.
{"title":"Thermal Activation of Zirconium(IV) Acetylacetonate Catalysts to Enhance Polyurethane Synthesis and Reprocessing","authors":"Subeen Kim, Jeremy L. Swartz, Oliver Sala, Molly Sun, Alexander K. Oanta, Jacob P. Brutman, Alaaeddin Alsbaiee, William R. Dichtel","doi":"10.1021/acs.macromol.4c00625","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00625","url":null,"abstract":"Carbamate formation and exchange catalysts enable efficient polyurethane (PU) manufacturing, as well as emerging recycling and reprocessing methods for PU thermosets. Zirconium β-diketonate complexes, such as Zr acetylacetonate [Zr(acac)<sub>4</sub>], are effective alternatives to toxic organotin catalysts that have been used for PU reprocessing. Here, we report that Zr(acac)<sub>4</sub> undergoes a thermally activated process in the PU network during reprocessing that transforms it into a more active carbamate exchange catalyst. This process is associated with the irreversible loss of acetylacetonate ligands and is not observed for the more sterically hindered Zr 2,2,6,6-tetramethyl-3,5-heptanedione [Zr(tmhd)<sub>4</sub>] complex. Crossover experiments between PU thermoplastics indicated enhanced carbamate exchange after the thermal activation of Zr(acac)<sub>4</sub> in the presence of one of the PUs, whereas a sample of Zr(acac)<sub>4</sub> activated in the absence of the PU had no catalytic activity. Thermal gravimetric analysis suggested that this process is associated with the loss of one protonated acac ligand. Stress relaxation analysis of PU thermosets indicated a distinct change in the characteristic relaxation time associated with the thermal activation of Zr(acac)<sub>4</sub> at temperatures above 140 °C; no such change was observed for samples reprocessed using Zr(tmhd)<sub>4</sub>. Density functional theory and molecular experiments suggest that irreversible ligand exchange of acac with alkoxide or carbamate reduces the activation energy for urethane formation and reversion. Furthermore, the Zr(acac)<sub>4</sub> catalyst activated in the presence of a PU’s polyol precursor provided more porous and less dense PU foams compared to those made using the unactivated Zr(acac)<sub>4</sub> catalyst. These findings are important for developing improved PU synthesis and recycling processes. Thermally activating a catalyst during reprocessing may provide more nuanced control of the in-use and reprocessing characteristics of PU thermosets.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141463758","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 : 2024-06-28DOI: 10.1021/acs.macromol.4c00641
Chenguang Yang, Dechang Tao, Fang Wang, Xin Wen, Ting Hu, Zhiyao Li, Kun Yan, Wenwen Wang, Dong Wang
Ultrahigh-molecular-weight polyethylene (UHMWPE) fibers with high creep resistance are widely used in ocean mooring cables, ship cables, and marine fisheries. Conventional methods of preparing creep-resistant UHMWPE fibers focus on postmodification, which significantly limits application in complex environments. Therefore, in this study, we prepared highly creep-resistant UHMWPE fibers with a molecular structure similar to that of a fish skeleton. First, the components of the spinning solution were combined proportionally, and an initiator and 1-hexene were added in varying amounts. Modified UHMWPE fiber products with polymer chain slip hindrance were prepared by melt-grafting spinning and hyperthermal drafting. The elongation declined markedly when the content of the added monomer increased to 5.0%, and the elongation decreased from 8.5 to 2.5% at a temperature of 70 °C, representing an improvement of more than 70%. This method solves the low efficiency problems encountered in conventional industrial modification methods, difficulty in modification via online spinning, and high creep resistance. This method is simple, cost-effective, and universally applicable.
{"title":"Ultrahigh-Molecular-Weight Polyethylene Fibers with Excellent Creep Resistance Derived from an Online-Tailored Fish-Skeleton-like Molecular Structure","authors":"Chenguang Yang, Dechang Tao, Fang Wang, Xin Wen, Ting Hu, Zhiyao Li, Kun Yan, Wenwen Wang, Dong Wang","doi":"10.1021/acs.macromol.4c00641","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00641","url":null,"abstract":"Ultrahigh-molecular-weight polyethylene (UHMWPE) fibers with high creep resistance are widely used in ocean mooring cables, ship cables, and marine fisheries. Conventional methods of preparing creep-resistant UHMWPE fibers focus on postmodification, which significantly limits application in complex environments. Therefore, in this study, we prepared highly creep-resistant UHMWPE fibers with a molecular structure similar to that of a fish skeleton. First, the components of the spinning solution were combined proportionally, and an initiator and 1-hexene were added in varying amounts. Modified UHMWPE fiber products with polymer chain slip hindrance were prepared by melt-grafting spinning and hyperthermal drafting. The elongation declined markedly when the content of the added monomer increased to 5.0%, and the elongation decreased from 8.5 to 2.5% at a temperature of 70 °C, representing an improvement of more than 70%. This method solves the low efficiency problems encountered in conventional industrial modification methods, difficulty in modification via online spinning, and high creep resistance. This method is simple, cost-effective, and universally applicable.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141464081","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}
Conformational characteristics and conformation-dependent properties of poly(ethylene 2,5-furandicarboxylate) (PEF), poly(trimethylene 2,5-furandicarboxylate) (PTF), and poly(butylene 2,5-furandicarboxylate) (PBF) have been revealed via NMR experiments and molecular orbital calculations on their model compounds, along with refined rotational isomeric state calculations for the polymers. The O(CH2)yO (y = 2, 3, and 4) segments of the polyesters exhibit conformational preferences similar to those found in the corresponding poly(alkylene terephthalate)s. The most stable conformations identified for PEF, PTF, and PBF are tg ± t, tg ± g ± t, and tg ± tg∓t, respectively. Their spatial configurations and conformational flexibilities significantly depend on conformations around the (furan)C–C(═O) bonds. Additionally, periodic density functional theory calculations were employed to optimize the α′ crystal structure of PEF, resulting in the equilibrium α form with a monoclinic lattice containing two all-trans chains. Young’s moduli along the a, b, and c axes of the optimized α crystal were calculated to be 26.8, 12.5, and 141 GPa, respectively. These values are comparable to those of poly(ethylene terephthalate).
{"title":"Insights into Conformation, Crystal Structure, and Material Properties of Plant-Derived Poly(alkylene 2,5-furandicarboxylate)s as Sustainable Alternatives to Petroleum-Derived Analogues","authors":"Mitsutoshi Hoshide, Hiromu Kawasaki, Shota Abe, Sayaka Iwabuchi, Shinnosuke Kogure, Yuji Sasanuma","doi":"10.1021/acs.macromol.4c00838","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c00838","url":null,"abstract":"Conformational characteristics and conformation-dependent properties of poly(ethylene 2,5-furandicarboxylate) (PEF), poly(trimethylene 2,5-furandicarboxylate) (PTF), and poly(butylene 2,5-furandicarboxylate) (PBF) have been revealed via NMR experiments and molecular orbital calculations on their model compounds, along with refined rotational isomeric state calculations for the polymers. The O(CH<sub>2</sub>)<sub><i>y</i></sub>O (<i>y</i> = 2, 3, and 4) segments of the polyesters exhibit conformational preferences similar to those found in the corresponding poly(alkylene terephthalate)s. The most stable conformations identified for PEF, PTF, and PBF are tg <sup>±</sup> t, tg <sup>±</sup> g <sup>±</sup> t, and tg <sup>±</sup> tg<sup>∓</sup>t, respectively. Their spatial configurations and conformational flexibilities significantly depend on conformations around the (furan)C–C(═O) bonds. Additionally, periodic density functional theory calculations were employed to optimize the α′ crystal structure of PEF, resulting in the equilibrium α form with a monoclinic lattice containing two all-trans chains. Young’s moduli along the <i>a</i>, <i>b</i>, and <i>c</i> axes of the optimized α crystal were calculated to be 26.8, 12.5, and 141 GPa, respectively. These values are comparable to those of poly(ethylene terephthalate).","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141462093","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 : 2024-06-27DOI: 10.1021/acs.macromol.4c01056
Manling Shi, Jing Sun, Qiang Fang
Alkyl side chains have been demonstrated to significantly affect the interchain packing of π-conjugated polymers, while their potential for modifying low-k materials remains unexplored. Herein, four low-k nonconjugated polymers based on the fluorenyl group with linear alkyl side chains of different lengths have been prepared. With the increase of the side chain length, their dielectric constants (Dk) gradually decrease. For example, when the side chains are butyl, hexyl, dodecyl, and octadecyl, the Dk values of the polymers are 2.62, 2.59, 2.50, and 2.45, respectively. Moreover, the polymers also display dielectric loss (Df) values of below 5.0 × 10–4 at 10 GHz. This discovery indicates that the alkyl side chains also have a big effect on the dielectric properties of the nonconjugated polymers via disrupting the close packing of the polymer chains, inducing the improvement of the dielectric properties of the polymers. This contribution provides a new strategy for the design of low-k materials used in the microelectronic industry.
烷基侧链已被证明会显著影响π-共轭聚合物的链间堆积，但它们在改性低k值材料方面的潜力仍有待开发。本文制备了四种基于芴基的低 k 非共轭聚合物，它们具有不同长度的线性烷基侧链。随着侧链长度的增加，它们的介电常数（Dk）逐渐降低。例如，当侧链为丁基、己基、十二烷基和十八烷基时，聚合物的 Dk 值分别为 2.62、2.59、2.50 和 2.45。此外，这些聚合物在 10 千兆赫时的介电损耗（Df）值也低于 5.0 × 10-4。这一发现表明，烷基侧链通过破坏聚合物链的紧密堆积，对非共轭聚合物的介电性能也有很大影响，从而改善了聚合物的介电性能。这一贡献为微电子工业中使用的低 K 材料的设计提供了一种新策略。
{"title":"Alkyl Side-Chain-Induced Improvement of Dielectric Properties of Polymers. 1. Fluorene–Benzocyclobutene-Based Polymers","authors":"Manling Shi, Jing Sun, Qiang Fang","doi":"10.1021/acs.macromol.4c01056","DOIUrl":"https://doi.org/10.1021/acs.macromol.4c01056","url":null,"abstract":"Alkyl side chains have been demonstrated to significantly affect the interchain packing of π-conjugated polymers, while their potential for modifying low-<i>k</i> materials remains unexplored. Herein, four low-<i>k</i> nonconjugated polymers based on the fluorenyl group with linear alkyl side chains of different lengths have been prepared. With the increase of the side chain length, their dielectric constants (<i>D</i><sub>k</sub>) gradually decrease. For example, when the side chains are butyl, hexyl, dodecyl, and octadecyl, the <i>D</i><sub>k</sub> values of the polymers are 2.62, 2.59, 2.50, and 2.45, respectively. Moreover, the polymers also display dielectric loss (<i>D</i><sub>f</sub>) values of below 5.0 × 10<sup>–4</sup> at 10 GHz. This discovery indicates that the alkyl side chains also have a big effect on the dielectric properties of the nonconjugated polymers via disrupting the close packing of the polymer chains, inducing the improvement of the dielectric properties of the polymers. This contribution provides a new strategy for the design of low-<i>k</i> materials used in the microelectronic industry.","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141462055","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：