Publications by authors named "Yijing Nie"

Article Synopsis
  • Scientists have made big improvements in a new type of material called molecular ferroelectrics, which can create power like some ceramics used today.
  • They've created a special flexible material using a soft plastic called TPU that helps these ferroelectrics work better and be more durable.
  • This new material can produce a lot more power—about 2000 times stronger than some current flexible materials—making it a great option for future gadgets and devices!
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Recently, metal-organic frameworks (MOFs) have attracted great interest in energy storage areas. However, the poor structural stability of MOFs derived from weak coordination bonds limits their applications. Here, quadruple hydrogen bonds (H-bonds) were introduced onto the MOFs to enhance their structural stability.

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The preparation of polymers with high self-healing ability is conducive to environmental protection and resource conservation. In the present work, two kinds of polyurethane (PU) elastomers were prepared: the one containing flexible end blocks (polypropylene glycol) and the other containing flexible end blocks and 2-ureido-4[1]-pyrimidinone (UPy) groups that can form reversible quadruple hydrogen bonds. Both of the two PU elastomers have self-healing ability.

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In the present work, we used molecular dynamics simulations to study the effects of carbon nanotube (CNT) contents on stretch-induced crystallization behavior in CNT filled polyethylene systems. During high-temperature stretching, the stretching is responsible for the orientation of CNTs, which then facilitates segment orientation and conformational transition from the -conformation into the -conformation in interfacial regions. The systems with higher CNT contents have a higher degree of orientation and higher contents of -conformation during stretching, resulting in the formation of more precursors.

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Polymer crystallization under chain and space confinements is studied by Monte Carlo simulation. The simulation results show that the crystallinity and melting temperature of confined systems increase with the increase of free chain content. Furthermore, the crystallinity and melting temperature of confined systems with larger lateral size are higher than those with smaller lateral size.

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Article Synopsis
  • Research is focusing on how to control the formation of stereocomplex crystallites (SCs) in blends of enantiomeric PLA.
  • Dynamic Monte Carlo simulations were used to explore how the number of blocks and crystallization temperature affect SC formation in multiblock copolymers.
  • When the block length is longer than the crystal thickness, increasing temperature and block number enhances SC formation due to greater supercooling and improved miscibility; however, when they are equal, the system reaches a limit where additional changes don't improve SC formation.
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The presence of nanofillers, such as graphene, can effectively promote stereocomplex formation in poly(l-lactide)/poly(d-lactide) blends. However, the detailed microscopic mechanism of the improved formation of stereocomplex crystallites (SCs) in filled polylactides is still unclear. Therefore, we performed dynamic Monte Carlo simulations to reveal the underlying mechanism of the effect of two-dimensional nanofillers on the formation of SCs in polymer blends.

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The influence of methylol and phenolic hydroxyl on the thermal properties of polybenzoxazines has been studied using two monofunctional benzoxazine monomers synthesized from methylol-/ethyl- phenol, aniline and paraformaldehyde. The chemical structures of the synthesized monomers are confirmed by H nuclear magnetic resonance (NMR), C NMR and Fourier transform infrared spectroscopy (FT-IR). Polymerizations are monitored by differential scanning calorimetry (DSC).

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Nowadays, it is a research hotspot to realize the controllability of polymer crystal structure in polymer nanocomposites. However, polymer crystals induced by two-dimensional filler always exhibit random orientation, which somewhat limit the improvement of physical properties of polymer materials. In the current paper, dynamic Monte Carlo simulations were performed to explore the methods preparing crystals with uniform orientation.

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The coexistence of nanofillers and shear flow can influence crystallization of polymer melts. However, the microscopic mechanism of the effect is not completely revealed yet. Thus, dynamic Monte Carlo simulations were used to study the effect of the filler networks formed by one-dimensional nanofillers on relaxation and crystallization of oriented polymer melts.

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We performed dynamic Monte Carlo simulation to investigate the micro-structural evolutions of polymers during glass transition. A new parameter, probability of segment movement, was proposed to probe the heterogeneity of local segment dynamics. A microscopic picture of spatial distribution of dynamic heterogeneity was obtained.

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Industrial semi-crystalline polymers contain various kinds of sequence defects, which behave like non-crystallizable comonomer units on random copolymers. We performed dynamic Monte Carlo simulations of strain-induced crystallization of random copolymers with various contents of comonomers at high temperatures. We observed that the onset strains of crystallization shift up with the increase of comonomer contents and temperatures.

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In this Article, we report the first study of the molecular dynamics in the glass-rubber transition region in polyisobutylene by 2D correlation dynamic mechanical spectroscopy (2DC-DMS). With the help of the high resolution and high sensitivity of the technique, the sub-Rouse modes are independently separated from the Rouse modes and local segmental motion (LSM). According to the positions and widths of autopeaks of three modes of molecular motions, the loss tangent peak is resolved into three peaks by nonlinear fitting method.

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In situ studies of strain-induced crystallization in unfilled and multiwalled carbon nanotube (MWCNT)-filled natural rubber (NR) were carried out by using synchrotron wide-angle X-ray diffraction (WAXD). Synchrotron WAXD results indicate that more nuclei appear in the MWCNT-filled NR sample, leading to higher crystallinity, lower onset strain of crystallization, and remarkable enhancement in tensile strength. During deformation, despite the amorphous chains remaining in isotropic orientation, the domains of larger scale (10-100 nm) with high network chain density in the NR matrix are oriented.

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