MACROMOLECULES
·
2013
·
IF 5.521
Wenwen Yu,Miao Du,Dezhi Zhang,Yu Lin,Qiang Zheng
The effect of dangling chains on phase-separated microstructure and molecular dynamics for polyurethanes (PUs) was investigated. PUs with different dangling chain lengths and polar groups were prepared through changing the types of diol extender. The molecular dynamics was studied by a combination of dynamic mechanical analysis (DMA) and broadband dielectric relaxation spectroscopy (BDRS). Four relaxations (processes), namely, a secondary relaxation (β), the soft phase segmental relaxation (α), the I process associated with hydrogen bond, and Maxwell–Wagner–Sillars (MWS) interfacial polarization process caused by charge accumulation at hard/soft phase interfaces, were detected. The I process occurred in temperatures lower than that of MWS process but higher than α relaxation in general. The β relaxation remains unaffected with changing dangling chain lengths or polar groups. However, the glass transition temperature (Tg) of the soft phase shifts to lower temperature, and the segmental motion becomes faster with increasing dangling chain length, while the introduction of a polar ester group into the dangling chains makes it slow down, corresponding to a higher Tg, and results in a higher fragility. On the other hand, there is an absence of I process, and the MWS process shifts to higher frequencies when longer dangling chain is introduced. In the case of increasing the hard segment content, the I process reappears and the MWS process slows down. It is suggested that these results are related to the H-bond interactions within hard segments and the micromorphologies of PUs.
研究领域:
材料科学
·
高分子化学
✓ 已验证
DOI
高影响因子
Materials
·
2024
·Vol. 17
·期 20
·5062
·
IF 3.1
Yan Li,Haibo Feng,Jing Xiong,Li Li
Classical viscoelastic models usually only consider the motion of chain segments and the motion of the entire molecular chain; therefore, they will cause inevitable errors when modeling self-healing vitrimer materials with many group movements. In this paper, a group-enriched viscoelastic model is proposed for self-healing vitrimers where the group effect cannot be neglected. We synthesize a specific damping vitrimer with many dangling chains, surpassing the limited loss modulus of conventional engineering materials. Due to the dangling chains, the damping capability can be improved and the group effect cannot be neglected in the synthesized damping vitrimer. The group-enriched viscoelastic model accurately captures the experimental damping behavior of the synthesized damping vitrimer. Our results indicate that the group-enriched viscoelastic model can improve the accuracy of classical viscoelastic models. It is shown that the group effect can be ignored at low frequencies since the chain segments have sufficient time for extensive realignment; however, the group effect can become significant in the case of high frequency or low temperature.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Polymer Chemistry
·
2022
·Vol. 13
·期 29
·4260-4272
·
IF 5.364
Haoxiang Rong,Min Xu,Xiaolin Jiang,Xun Lu
Damping elastomers are widely used to control vibration and noise in various fields. However, there are common issues of weak damping temperature range controllability and poor mechanical properties as well as insufficiently tailored molecular structures in high-damping elastomers. Therefore, we have introduced poly(ethylene glycol) monomethyl ether (MPEG) dangling chains and dynamic disulfide bonds to synthesize polyurethane elastomers with an effective damping (tan δ ≥ 0.3) temperature range of 143 °C (−43–100 °C) and a high mechanical strength of 11.43 ± 0.51 MPa. To further probe the effect of dangling chains and dynamic disulfide bonds on the multi-scale molecular structure and properties of PU damping material, the molecular dynamics and dynamic mechanics were analyzed by combining dynamic mechanical analysis (DMA) and broadband dielectric relaxation spectroscopy (BDRS). The Maxwell–Wagner–Sillars (MWS) interfacial polarization process was observed in a PU elastomer after introducing the dangling chains, indicating a lower degree of microphase separation and faster segmental motion to improve the damping properties. After introducing disulfides, the dynamic exchange of disulfides is helpful for segmental motion to increase molecular chain friction and mechanical energy consumption. The relationship among the multi-scale chain structure, phase morphology and damping properties was revealed, thus providing a theoretical basis and technical reference in the development of novel high-damping materials.
研究领域:
材料科学
·
高分子化学
✓ 已验证
DOI
高影响因子
POLYMER
·
2014
·
IF 3.766
Wenwen Yu,Miao Du,Weijuan Ye,Weiyang Lv,Qiang Zheng
A series of dangling chain based-polyurethane/poly(methyl methacrylate) (DPU/PMMA) filled with exfoliated layered double hydroxides (LDH) were synthesized by methyl methacrylate in-situ intercalative polymerization. The dangling chains were introduced by using vegetable oils as chain extender . The effect of dangling chain and the contents of LDH on the molecular dynamics of DPU/PMMA was investigated by a combination of dynamic mechanical analysis and broadband dielectric relaxation spectroscopy. Compared with polyurethane/poly(methyl methacrylate) (PU/PMMA) without dangling chain, the glass transition temperature ( T g ) of DPU/PMMA shifts to lower temperature and the segmental dynamics becomes faster. A plateau with a high loss factor value above T g significantly broadens the damping temperature range due to the synergy effect between the dangling chains and LDH layers. In DPU/PMMA/LDH nanocomposites, the α -relaxation associated with the glass transition of the polymer matrix becomes slower with the increase of LDH content, which indicates a restricted molecular mobility in the interfacial regions between polymer and LDH. However, the local relaxations at relatively low temperature remain unaffected by dangling chain or the addition of LDH. When the LDH content increases, Maxwell–Wagner–Sillars (MWS) interfacial polarization process caused by charge accumulation at interfaces becomes faster because of the smaller mean distance d between the exfoliated LDH layers.
研究领域:
材料科学
·
高分子化学
✓ 已验证
DOI
高影响因子
POLYMER TESTING
·
2023
·
IF 5.1
Xiaohao Tang,Xin Guo,Xiao Liu,Guangye Liu,Li Liu,Baogang Zhang
In order to overcome the sharp damping peak that limits the application of polyurethane elastomers (PUE) and the cut that affects its service life as functional floor coating, a self-healing PUE with broader damping temperature range and high self-healing efficiency was prepared by incorporation of prepolymer synthesized from polycaprolactone diol and isophorone diisocyanate and chain extenders including 4,4′-diaminodiphenyl disulphide (DAPS) and double-hydroxyl suspended chains synthesized from IPDI, polyethylene glycol monomethyl ether and 2-amino-1,3-propanediol. The effects of different functionalities were carefully investigated at the fixed dosage of 30%. DAPS with dynamic disulfide bonds were revealed of higher efficiency in improving the damping properties and self-healing rate. The synergistic effects of the two functionalities were studied by varying the usage of DAPS from 10% to 50% when the suspension chain amount fixed at 30%. The effective damping (tan δ > 0.3) domain presents a range of 131.57 °C with 100% increase of tan δ compared with the base sample, and the self-healing efficiency reaches 95% when the usage of DAPS and suspension chain were 30% and 50%, respectively. The modified material achieved prominent improvement in damping properties and cut self-healing ability, showing potential application in aerospace and acoustic coatings for vibration and noise reduction.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
POLYMER
·
2025
·
IF 4.5
Hang Ye,Chen Qiu,Long Ni,Ke Yang,Hongbin Tian,Xinyang Luo,Mei Liang,Shengtai Zhou,Yinfu Luo,Huawei Zou
Energy absorption and dissipation are enhanced by the extension of the free volume of chain segments through hanging chains, which is key to improving the damping performance of rigid polyurethane foams (RPUFs). A series of multi-functional RPUFs with integrated thermal insulation, mechanical and damping properties were prepared by introducing different types of chain extenders as dangling chains. The effects of different pendant chains on the foaming process, crosslinking network, microstructure, mechanical properties, thermal insulation performance and damping properties of RPUF were investigated. The synergistic influence of the spatial site-blocking effect, dilution of polar groups, and improvement of compatibility between soft and hard segments is essential for improving the overall performance. The integration of elongated dangling chains impedes the agglomeration of rigid regions within RPUFs, thereby enhancing the crosslinking structure. RPUF-OG exhibited excellent mechanical, thermal insulation, and damping properties, with a compressive strength of 1.34 MPa, a thermal conductivity of 0.0416 W/(m·K), and a maximum damping factor of 0.40 .This work proposed a strategy to fabricate RPUFs with integrated mechanical, thermal insulation, and damping properties by introducing dangling chains, providing promising solutions for applications in aerospace and transportation industries in terms of structural support, thermal insulation and vibration damping.
研究领域:
高分子材料科学
·
功能材料
·
热学性能
·
力学性能
·
振动控制
·
多孔材料
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）