Cyclic Poly Ethylene Research Articles

State Transitions and Crystalline Structures of Single Polyethylene Rings: MD Simulations.

This study investigates the structural changes of cyclic polyethylene (PE) single chains during cooling through molecular dynamics simulations. The influence of topological constraint on a ring is examined by comparing it with the results of its linear counterpart. A pseudo phase diagram of state transition for PE rings based on length and temperature is constructed, revealing a consistent chain-folding transition during cooling. The shape anisotropy of short crystallized cyclic chains exhibits oscillations with chain length, leading to a more pronounced odd-even effect in single cyclic chains compared with the linear ones. A honeycomb model is proposed to elucidate the odd-even effect of chain folding in crystalline structures of single linear and cyclic chains, and we discuss its potential to predict surface tension. Analyses of the tight folding model and the re-entry modes demonstrate that a cyclic chain possesses a shorter average crystalline stem length and a more compact folded structure than its linear counterpart. The findings highlight the impact of topological change on crystallization and the odd-even effect of chain length, providing valuable insights for understanding polymer crystallization with different topologies.

Role of Entanglement Species in the Formation of Shish-Like Fibril Crystals Elucidated by Cyclic Polyethylene

Role of Entanglement Species in the Formation of Shish-Like Fibril Crystals Elucidated by Cyclic Polyethylene

Molecular dynamics simulation on the crystallization behavior of cyclic polyethylene affected by functionalized carbon nanotubes

AbstractIn this work, the effects of functionalized carbon nanofillers (i.e., CNT‐g‐PE prepared by carbon nanotubes grafted with linear polyethylene) on the crystallization of cyclic polyethylene were revealed by molecular dynamics simulation, and compared with that of pure cyclic polyethylene(C‐PE) and carbon nanotube / cyclic polyethylene blends(C‐PE/CNT). The simulation results show that the CNT‐g‐PE has an anti‐nucleation effect on the cyclic polyethylene, the crystallinity and crystallization rate of the C‐PE/CNT‐g‐PE system are significantly lower than those of the other systems. This phenomenon can be explained by the topological effect when linear polyethylene chains grafted on carbon nanotubes are mixed with cyclic polyethylene. It is observed from the micro‐scale that when the linear polyethylene chains are in contact with cyclic polyethylene, the cyclic chains are passed through by the linear chains to form a transient entanglement network, further affecting the dynamic process of the molecular chains. The diffusion and orientation of the cyclic polyethylene molecular chain are inhibited. This limits the crystal nucleation efficiency and growth kinetics. These simulation results not only support some experimental findings, but also confirm some microscopic phenomena that are difficult to observe in the experiment, which provides some inspirations for the experimental design of high‐performance nanocomposite materials.

Stretching-induced nucleation and crystallization of cyclic polyethylene: Insights from molecular dynamics simulation

Stretching-induced nucleation and crystallization of cyclic polyethylene (PE) were investigated by molecular dynamics (MD) simulation. The results show that nucleation and crystallization of cyclic PE are intimately related to the molecular weight of chains and strain rate. We found that there exists a critical molecular weight, below which increasing the molecular weight leads to the increase of crystallization rate and above which increasing the molecular weight leads to the slowdown of crystallization rate. This is caused by the fact that when the chain length is short, it is difficult to form a stable crystal nucleus because of its strong movement ability, while when the chain length is long, it hinders the conformational transformation and orderly arrangement of chain segments due to its reduced movement ability. The more the content of segments with longer conformational ordered segments and higher orientation in the system, the more conducive to the formation of more stable nuclei. Cyclic PE systems tend to form crystal nuclei through intramolecular nucleation with the increases of chain length. In addition, stretching will cause the chains to be disentangled and orderly arranged along the stretching direction to form crystal regions. The crystallization ability of the system will deteriorate with the acceleration of strain rate. This is because when the strain rate is low, it takes a long time to stretch to the same strain, and there is enough time to be stretched, resulting in more stretching of the chains and an increase in the probability of orderly arrangement of chain segments, so it is easier to orientation and crystallization. The opposite is true when the strain rate is high.

Metal-Organic Frameworks for Practical Separation of Cyclic and Linear Polymers.

The purification step in the manufacturing of cyclic polymers is difficult as complete fractionation to eliminate linear impurities requires considerable effort. Here, we report a new polymer separation methodology that uses metal-organic frameworks (MOFs) to discriminate between linear and cyclic polyethylene glycols (PEGs) via selective polymer insertion into the MOF nanopores. Preparation of a MOF-packed column allowed analytical and preparative chromatographic separation of these topologically distinct pairs. In addition, gram-scale PEGs with only cyclic structures were successfully obtained from a crude reaction mixture by using MOF as an adsorbent.

Metal‐Organic Frameworks for Practical Separation of Cyclic and Linear Polymers

AbstractThe purification step in the manufacturing of cyclic polymers is difficult as complete fractionation to eliminate linear impurities requires considerable effort. Here, we report a new polymer separation methodology that uses metal‐organic frameworks (MOFs) to discriminate between linear and cyclic polyethylene glycols (PEGs) via selective polymer insertion into the MOF nanopores. Preparation of a MOF‐packed column allowed analytical and preparative chromatographic separation of these topologically distinct pairs. In addition, gram‐scale PEGs with only cyclic structures were successfully obtained from a crude reaction mixture by using MOF as an adsorbent.

Gold nanoparticles endowed with low-temperature colloidal stability by cyclic polyethylene glycol in ethanol

The colloidal stability of metal nanoparticles is tremendously dependent on the thermal behavior of polymer brushes. Neat polyethylene glycol (PEG) presents an unconventional upper critical solution temperature in ethanol, where phase segregation and crystallization coexist. This thermal behavior translated to a PEG brush has serious consequences on the colloidal stability in ethanol of gold nanoparticles (AuNPs) modified with PEG brushes upon cooling. We observed that AuNPs (13 nm diameter) stabilized with conventional linear PEG brushes (Mn = 6 and 11 kg mol-1) in ethanol suffer from reversible phase separation upon a temperature drop over the course of a few hours. However, the use of a polymer brush with cyclic topology as a stabilizer prevents sedimentation, ensuring the colloidal stability in ethanol at -25 °C for, at least, four months. We postulate that temperature-driven collapse of chain brushes promotes the interpenetration of linear chains, causing progressive AuNP sedimentation, a process that is unfavorable for cyclic polymer brushes whose topology prevents chain interpenetration. This study reinforces the notion about the importance of polymer topology on the colloidal stability of AuNPs.

Cyclic Polyethylene Glycol as Nanoparticle Surface Ligand.

Cyclic polymers behave different than linear polymers due to the lack of end groups and smaller coil dimensions. Herein, we demonstrate that cyclic polyethylene glycol (PEG) can be used as an alternative of classical linear PEG ligands for gold nanoparticle (AuNP) stabilization. We observed that the brush height of cyclic PEG on AuNPs of diameter 4.4 and 13.2 nm increases identically as that of linear brushes with (Nσ1/2)0.7 (N, number of monomers in a chain and σ, grafting density) and that cyclic brushes are more stretched than their linear analogues when compared to their unperturbed dimensions. Such structural effect and the reduced footprint diameter in cyclic brushes with the entire chain in a concentrated polymer brush regime explains the distinct response of NPs to ionic strength and temperature, respectively, compared to linear analogues. These experiments are an important step in understanding the effect of polymer brush topology on colloidal properties.

Preparation of polypseudorotaxane composed of linear and cyclic polyethylene oxides and its application to solid polymer electrolyte

AbstractThe mixture of linear polyethylene glycol with molecular weight of 20,000 (l‐PEG20K) and cyclic polyethylene glycol with molecular weight of 1,000 (c‐PEG1K) was ultrasonicated in acetonitrile. After evaporating the solvent, the residue was analyzed by DSC to show a remarkable decrease of crystallization temperature. Such a large crystallization suppression was not observed when linear polyethylene glycol with molecular weight of 1,000 (l‐PEG1K) was added instead of c‐PEG1K. Further, the mixture of cyclic polyethylene glycols (c‐PEG6K and c‐PEG1K) did not exhibit a significant crystallization suppression. These experimental results indicated that formation of polypseudorotaxane through ultrasonication‐assisted ring penetration played an important role in the crystallization suppression. Ionic conductivities of the polypseudorotaxane‐based polymer electrolytes prepared from polyethylene oxide with molecular weight of 600,000 (PEO600K) and c‐PEG1K showed conductivity enhancement especially at low Li salt concentration.

Molecular simulation of structural and dynamic properties of polymer nanoparticles composed of linear and cyclic polyethylene

Polymer nanoparticles were investigated using Monte Carlo simulation of coarse-grained linear and cyclic polyethylene (PE). The method employs the Flory’s rotational isomeric state (RIS) model and Lennard-Jones potential; respectively, for intra- and inter-molecular interaction. The density of nanoparticle with cyclic chains is slightly higher than that of linear polymers, and the interfacial region is slightly narrower. Structural and orientational properties of linear and ring chains are quite similar. Increased mobility toward the free surface on the scale of beads, bonds and chain is due to the decrease in density. Cyclic polymers move slower than the linear chains. The region of an increased mobility is deeper than the bond length and is attributed to the low density in the surface region rather than to the segregation of chain ends. Rotational and translational motion are faster for linear chains before the molecules encounter the confinement effect of nanoparticles, then there is the cross-over point and chains move slower.

Influence of the Hydro/Fluorocarbon Chain Length on CMC and HLB of Surface-Active Nonionic Surfactants Containing Polyethylene Glycol Groups

AbstractSeries of cyclic polyethylene glycol succinates based surfactants bearing a hydro- or fluorocarbon group was synthesized and characterized. Evaluation of the surface-active properties of the obtained compounds reveals, (i) the surface tension decreases gradually when is the length of the lipophilic chain increased (ii) the critical micelle concentration (CMC) increases with the number of ethylene oxide unit present in the polar head and (iii) surface tension follows the increasing pattern of hydrophilic-lipophilic balance (HLB) number.

Synthesis and Surface‐Active Properties of F‐Alkylated Polar Loops

AbstractThe synthesis of double tail surfactants having crown ethers as polar heads was performed by reacting di‐F‐alkyl mercaptosuccinate on cyclic polyethylene glycol maleates. Surface tension and critical micelle concentration (CMC) were determined for these new surfactants. According to CMC values, the solubility in water is higher with perfluoroalkyl surfactants having a bigger loop size and shorter hydrophobic chains.

環状ポリエチレンの球晶成長速度から探る高分子の結晶成長に及ぼすトポロジカルな拘束と結び目絡み合いの効果

環状ポリエチレンの球晶成長速度から探る高分子の結晶成長に及ぼすトポロジカルな拘束と結び目絡み合いの効果

Silica-Polyethyleneglycols/N 2 O 4 Complexes as Heterogeneous Nitrating and Nitrosating Agents

Silica-chloride was reacted with different quantities of H(OCH 2 CH 2 ) n OH (n = 2-4) to furnish silica-based linear polyethylene glycols and cyclic polyethylene glycolic ethers. The N 2 O 4 complex of silica-tetraethylene glycolic ether ( III ) was selected and used as a stable, cheap, and heterogeneous silica-based reagent for the selective mono- and dinitration of phenols and nitrosation of thiols.

Cationization Processes in Matrix‐assisted Laser Desorption/Ionization Mass Spectrometry: Attachment of Divalent and Trivalent Metal Ions

In this paper, divalent and trivalent metal ions have been used as cationization reagents in matrix-assisted laser desorption/ionization (MALDI) experiments. Analytes studied include polyethylene glycol, polyethylene oxide dimethyl ether, cyclic polyethylene oxide and α-cyclodextrin. Independent of the valence of the metal ions and the nature of the analyte molecules studied, singly charged quasimolecular ions were generated in all cases. These quasimolecular ions were shown to be generated in different forms depending on the type of the di- or trivalent metal salts and the chemical properties of the analyte molecules. For Cu2+ ions, the quasimolecular ions were formed by the adduction of the reduced metal ions, i.e. Cu+. For Pb2+, Cd2+, Ba2+, Sr2+ and La3+ ions, singly charged quasimolecular ions were formed by adduction of the metal ions with either simultaneous deprotonation of the analyte molecule or adduction of an additional deprotonated matrix moiety onto the analyte molecule. Of these two choices, deprotonation of the analyte molecule is always preferred if labile protons, such as those in hydroxyl groups, are available in the analyte molecule. A model of ion formation from MALDI based on solid-state molecular pre-arrangement is used to account for the formation of such complex singly charged quasimolecular ions. © 1997 John Wiley & Sons, Ltd.

Cationization Processes in Matrix-assisted Laser Desorption/Ionization Mass Spectrometry: Attachment of Divalent and Trivalent Metal Ions

In this paper, divalent and trivalent metal ions have been used as cationization reagents in matrix-assisted laser desorption/ionization (MALDI) experiments. Analytes studied include polyethylene glycol, polyethylene oxide dimethyl ether, cyclic polyethylene oxide and α-cyclodextrin. Independent of the valence of the metal ions and the nature of the analyte molecules studied, singly charged quasimolecular ions were generated in all cases. These quasimolecular ions were shown to be generated in different forms depending on the type of the di- or trivalent metal salts and the chemical properties of the analyte molecules. For Cu2+ ions, the quasimolecular ions were formed by the adduction of the reduced metal ions, i.e. Cu+. For Pb2+, Cd2+, Ba2+, Sr2+ and La3+ ions, singly charged quasimolecular ions were formed by adduction of the metal ions with either simultaneous deprotonation of the analyte molecule or adduction of an additional deprotonated matrix moiety onto the analyte molecule. Of these two choices, deprotonation of the analyte molecule is always preferred if labile protons, such as those in hydroxyl groups, are available in the analyte molecule. A model of ion formation from MALDI based on solid-state molecular pre-arrangement is used to account for the formation of such complex singly charged quasimolecular ions. © 1997 John Wiley & Sons, Ltd.