MACROMOLECULES
·
2019
·
IF 5.997
Yuming Chen,Peng Liang,Zhen Yue,Wei Li,Chuanding Dong,Binbo Jiang,Jingdai Wang,Yongrong Yang
Chain entanglement was very important for adjusting the processability and mechanical property of nascent ultrahigh molecular weight polyethylene (UHMWPE). So far, it is still a mystery to unravel the formation mechanism of entanglements when the ethylene polymerization is conducted by the heterogeneous catalysts. In this study, a series of weakly entangled UHMWPE was synthesized by the polyhedral oligomeric silsesquioxane/MgCl2 nanoaggregates modified Ziegler–Natta catalysts. The structure of nanoaggregates was evaluated by X-ray photoelectron spectroscopy, density functional theory simulations, and scanning probe microscope experiments, where the coordination strategy of MgCl2 and hydroxyl of POSS was investigated. These nanoaggregates presented extremely low activity on ethylene polymerization and were proved to serve as isolators for separating the active sites and growing chains. The entanglement density of nascent UHMWPE (reflected by the value of initial storage modulus G′(t=0)) was exponentially decayed with the polymerization activity of increased numbers of nanoaggregates. Importantly, this exponentially decayed effect contributed by increased numbers of POSS/MgCl2 isolators offset the rapid power function increment of entanglements upon rising the temperature, which was the essential reason for the successful synthesis of weakly entangled UHMWPE even at 85 °C. Finally, we have proposed the dependence and sensitivity of G′(t=0) (i.e., indicating the initial entanglement density of nascent polymers) on the polymerization activity, which was able to trace the formation of entanglements during polymerization through the POSS modified heterogeneous catalyst.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
MACROMOLECULES
·
2025
·
IF 5.2
Yifu Ruan,Hao Zhang,Qingzhi Zou,Pengfei Zhang,Rui Zhang,GengXin Liu
Polymer entanglements confer exceptional properties, but, at certain conditions, pose significant processing challenges. Disentangled polymers are thermodynamically unstable, leading to ambiguities in their dynamics. The soft nanoparticles (SNPs) may be considered a random coil stabilized by intramacromolecular cross-linking. As a model system of inhibited interpenetration, it could be used to illustrate the disentanglement and shed light on the boundary between polymers and colloids. We bring fractionation to SNPs and systematically curated over forty samples. Terminal relaxation time τ spanning nine decades was quantified while molecular mass spanning as narrow as two decades. Based on the analysis, governing equations for τ were established as functions of bulk diameter (Dbulk) and cross-linking strand length (Nc). We identify the parameter space capable of reducing τ 1000 times, defining the limits of disentanglement. Compared to linear polymers of equivalent molecular weights, lightly cross-linked polymeric nanoparticles exhibit significantly faster relaxation and improved processability. At larger Dbulk and Nc, τ shows a greater divergence than the mechanism of entanglements. Such precise fractionated SNPs are essential for achieving these quantitative insights.
研究领域:
高分子科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
MATERIALS LETTERS
·
2021
·
IF 3.423
Min Huang,Huan Shi,Ning Wei,Chunhui Luo,Faliang Luo
Polyvinyl alcohol (PVA) hydrogels have drawn enormous attention but are severely limited on account of poor mechanical properties at subzero temperatures. Here, we propose a simple method to tackle this problem by incorporating chain entanglements of PVA chains and coordination bonds between Al 3+ ions and –OH groups via air-drying and soaking in Al 2 (SO 4 ) 3 solution. The multiple dynamic interactions worked in tandem to achieve outstanding mechanical performance (41.0 MPa of fracture stress and 49.9 MJ/m 3 of toughness). Meanwhile, the introduction of ions endowed the PVA hydrogel with excellent anti-freezing property (36.9 MPa of fracture stress and 51.4 MJ/m 3 of toughness at −20 ℃), superior to most anti-freezing gels at subzero temperatures. The facile synthesis and superior properties might expand the application of PVA hydrogels.
研究领域:
材料科学
·
生物材料
✓ 已验证
DOI
高影响因子
Gels
·
2024
·Vol. 10
·期 12
·822
·
IF 5
Kai Hu,Qingyun Li,Xiaofan Ji
Hydrogels are widely used in the field of adhesive materials. However, hydrogel adhesion has previously required the covalent graft of supramolecular groups on polymeric chains. In contrast to that, here, a hydrogel adhesion induced by covalent polymer entanglement between two hydrogel networks was reported. HydrogelsG1andG2contain the monomersM1, with diazonium groups, andM2, with sulfonate groups, respectively. When the two hydrogels come into contact, the monomers diffuse into each other’s networks and assemble into supramolecular polymers (SPs) based on electrostatic interactions, threading the two hydrogel networks. Subsequently,SPsconvert into covalent polymers (CPs) under UV light stimulation due to the reaction between the diazonium groups and sulfonate groups, leading to the entanglement of the two hydrogel networks and the production of an adhesive effect. This finding provides a novel strategy for hydrogel adhesion.
研究领域:
材料科学
·
生物医学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
POLYMER
·
2025
·
IF 4.5
Xiaohuan Bu,Wei Zhao,Xin Li,Wenjie Zhang,Yuancheng Zhang,Ge Shi,Yanjie He,Zhe Cui,Peng Fu,Xinchang Pang,Hong Wu,Xiaomeng Zhang,Minying Liu
Polyamide 66 (PA66) with less entangled structure, high crystallinity and excellent mechanical properties was fabricated in this work by direct solid-state polymerization (DSSP) method. The polymerization process and mechanism of DSSP were systematically investigated. Results demonstrate that DSSP is a transition process from salt crystal directly to polymer crystal, enabling the production of PA66 with a less entangled and highly crystalline structure. DSSP sample exhibits a crystallinity of 51.8% as tested by WAXD, and 59.7% when measured via DSC, surpassing the crystallinity of the majority of PA66 fibers. Furthermore, the sample achieves a maximum melting point of 271.7 °C. Correspondingly, mechanical properties and heat distortion temperature of DSSP sample are also improved. Therefore, this work enhances the in-depth understanding of polymerization mechanism of DSSP, and provides an efficient, scalable approach for fabricating polymers with less entanglement, high crystallinity, and exceptional performance characteristics.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2022
·
IF 16.744
Min Jiang,Bo-Wen Liu,Feng-Ming He,Qin Zhang,Ao Wang,De-Ming Guo,Hai-Bo Zhao,Li Chen,Yu-Zhong Wang
Although conventional chemical copolymerization method has shown favorable results in improving certain performance of polymers, simultaneous improvement of overall properties is hardly achieved. Here, we reported a feasible method to fabricate high-performance polymers with great overall properties by simultaneously tailoring their chemical constitution and topological conformation. We designed and synthesized a novel functional monomer with a sidechain caged structure based on phosphorus chemistry, and prepared the corresponding aliphatic polyamide as a typical representative of thermoplastic synthetic polymers. The incorporation of a sidechain caged structure enhanced the chain entanglement of the resultant polyamide, thus improved the mechanical strength by 39% and largely enhanced the heat resistance. The great processability was basically uninfluenced due to the easy dissociation of the entanglement during processing, enabling the potentially wide application fields as both fibers and engineering plastics. Furthermore, based on the free radical scavenging effect of the phosphorus-based monomer, the flame retardancy of the resultant polyamide was significantly improved. In sight of these findings, this work provides a novel method for fabricating high-performance polymers for various applications.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
Nature Communications
·
2024
·Vol. 15
·期 1
·1-11
·
IF 14.7
Zhu Ruixin,Zhu Dandan,Zheng Zhen,Wang Xinling
Most tough hydrogels are reinforced by introducing energy dissipation mechanisms, but simultaneously realizing a high toughness and low hysteresis is challenging because the energy dissipation structure cannot recover rapidly. In this work, high mechanical performance highly entangled double network hydrogels without energy dissipation structure are fabricated, in which physical entanglements act as the primary effective crosslinking in the first network. This sliding entanglement structure allows the hydrogel network to form a highly uniform oriented structure during stretching, resulting in a high tensile strength of ~3 MPa, a fracture energy of 8340 J m −2 and a strain-stiffening capability of 47.5 in 90% water content. Moreover, almost 100% reversibility is obtained in this hydrogel via energy storage based on entropy loss. The highly entangled double network structure not only overcomes the typical trade-off between the high toughness and low hysteresis of hydrogels, but more importantly, it provides an insight into the application of entanglement structures in high-performance hydrogels.
研究领域:
材料科学
·
生物医学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF CATALYSIS
·
2018
·
IF 6.759
Wei Li,Lei Hui,Bing Xue,Chuanding Dong,Yuming Chen,Linxi Hou,Binbo Jiang,Jingdai Wang,Yongrong Yang
A Polyhedral oligomeric silsesquioxane (POSS) modified Ziegler-Natta catalyst is reported to synthesize the weakly entangled ultra-high molecular weight polyethylene at a high temperature and with a high activity. Incorporation of POSS can form numbers of aggregates with a mean size of 48 nm adsorbing on the surface of SiO 2 . The structure of nanoaggregates is evidenced by the experiments and theoretical calculations where one POSS can coordinate with multiple MgCl 2 molecules serving as an electric donor to the further immobilized TiCl 4 . The catalyst is thus featured by two distinct active regions positioned in the POSS/MgCl 2 nanoaggregates and δ -MgCl 2 , respectively. The former regions present extremely low activity on ethylene polymerization, which function as horizontal separators for isolating the active TiCl 4 sites and the growing chains. This catalyst exhibits an exceptional activity ( i.e. 1.3 × 10 6 gPE mol Ti −1 h −1 bar −1 ) for the synthesis of weakly entangled polyethylene at 60 °C.
研究领域:
材料科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF SURFACTANTS AND DETERGENTS
·
2019
·Vol. 22
·期 3
·587-595
·
IF 1.672
Mingwei Zhao,Zhibin Gao,Caili Dai,Xin Sun,Yue Zhang,Xiujie Yang,Yining Wu
Enhancing the viscoelastic properties of wormlike micelles by adding nanoparticles has been widely reported. Various mechanisms have been proposed to explain how nanoparticles strengthen the network formed by wormlike micelles. It remains unclear whether nanoparticles produce the same effect on systems with different entanglement degrees. To clarify this issue, the concentration of potassium chloride was used to control the entanglement degree of wormlike micelles. The rheological behavior of different nanoparticle-enhanced wormlike micellar systems (NEWMS) was investigated using rheology. Three critical parameters including zero-shear viscosity ( η 0 ), relaxation time ( τ R ), and contour length ( L ) were calculated to analyze the effect of nanoparticles on the different wormlike micellar systems. An appropriate mechanism describing the interaction between nanoparticles and wormlike micelles with different structures was proposed.
研究领域:
化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
MACROMOLECULES
·
2024
·
IF 5.1
Yifu Ruan,Qingzhi Zou,Haoyan Zhang,Yipeng Zhang,Hao Zhang,Weiwei Wu,Hao Liu,Jiajun Yan,GengXin Liu
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.
研究领域:
材料科学
·
高分子化学
·
流变学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Zhaorui Meng,Weihua Zhong,Dianbo Zhang,Qun Liu,Zhaoshuo Wang,Yandong Ma,Shichao Lu,Xu Hu,Tianying Sun
In extreme environments, it is difficult to balance the strength and toughness of ultra-thin film materials. To address this problem, we propose a promising strategy to build ultra strong, tough and extreme environments resistant Poly(p-phenylene-2,6-benzobisoxazole) (PBO) papers with a nacre-like structure constructed by synergistic electrostatic interaction and interlayer entanglement through the sol–gel-film method and hot press orientation. Highly interconnected PBO nanofibres （PNFs） with positive charges are tightly wound around the anisotropic graphene oxide (GO) nanosheets with negative charges through strong electrostatic interaction, forming a nacre like microstructure. The addition of Fe (Ⅲ) can form a coordination bond with the amino group on PNFs. Chemical crosslinking and hydrogen bonding synergize with interlayer entanglement effect among different PNFs，which can effectively dissipate interlayer energy and alleviate the conflict between strength and toughness. The resultant tensile strength and toughness are as high as 338.3 MPa and 16.04 MJ/m 3 ，which are 197.7 % and 425.4 % of those of the intrinsic PBO paper, respectively. Additionally, after 5000 folding-unfolding cycles, the tensile strength retention and toughness retention of the PBO/GO/Fe (PGFe) paper were still 85.4 % and 71.9 %, respectively. Moreover, the paper exhibits excellent tolerance to extreme temperature environments and showed extremely strong chemical stability.
研究领域:
材料科学
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2016
·Vol. 217
·期 19
·2139-2144
·
IF 2.495
Xiuyin Zhang,Chuanzhuang Zhao,Nanping Xiang,Wei Li
Physical interaction between the microgel and the hydrogel matrix is a key issue in the rational design of microgel reinforced hydrogels. A pentaerythritol-crosslinked poly(acrylic acid) (PAAc) microgel, named Carbopol, is composited with polyacrylamide (PAAm) hydrogel. The toughness of the hydrogel is significantly improved by constructing an interpenetrating network of Carbopol and PAAm. Chain entanglements within the composited hydrogel result in a strain-hardening phenomenon and an efficient stress transfer from the PAAm matrix to the sacrificing network of Carbopol. Hydrogen bonds between PAAc and PAAm can be formed in an acidic environment, which function as reversible sacrificing bonds and further improve the stretchability of the hydrogel.
研究领域:
材料科学
·
生物材料
✓ 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）