Ring Polymers: Effective Isolation and Unique Properties

Beckham, Haskell W.

doi:10.1002/9780470825150.ch26

Cited by 7 publications

(17 citation statements)

References 166 publications

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“…Loss of high molecular weight polymers during the filtration to remove Pd/C might be the cause of the decrease in M n . Monitoring the reaction progress by 1 H NMR spectroscopy indicates that after 2−4 d ∼80 % of the double bonds are saturated; however, to obtain 99% conversion, extended reaction time is required. Kamigaito et al 64 also noted the need for long reaction time for the hydrogenation of linear poly(β-pinene).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Compared to linear polymers, cyclic polymers , with the same number of repeat units have smaller pervaded volumes, and thus also have smaller radii of gyration (< R g >) − and intrinsic viscosities. , Lacking chain ends, cyclic polymers do not reptate, − and with fewer degrees of freedom, lower conformational flexibility, and increased chain stiffness, cyclic polymers exhibit higher glass-transition temperatures ( T g ) compared to their equivalent linear analogs. ,− By exploiting the inherent differences between linear and cyclic polymer topologies, the application of cyclic polymers in the areas of biological materials, , thermal plastics, and electronics, is flourishing. For example, Grayson et al discovered that cyclic poly(ethylene imine) has higher gene delivery efficiency and lower cytotoxicity when compared to its linear analog.…”

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confidence: 99%

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Cyclic Poly(4-methyl-1-pentene): Efficient Catalytic Synthesis of a Transparent Cyclic Polymer

et al. 2020

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Cyclic polymers possess properties that are significantly different from their linear analogs, such as higher densities, smaller hydrodynamic volumes, and higher glass transition temperatures. Poly(4-methyl-1-pentene) (PMP), a linear polyolefin, is a commercial transparent thermoplastic and has applications in packaging materials and release membranes. Polymerizing 4-methyl-1-pentyne with a tungsten alkylidyne catalyst and subsequent hydrogenation (>99%) provided cyclic poly(4-methyl-1-pentene) ( c-PMP). Evidence of a cyclic topology comes from rheology/viscosity studies, light scattering measurements, and size-exclusion chromatography. Importantly, atactic c-PMP exhibits a T g (39 °C) 10 °C higher than the linear analog. A 15 g-scale cyclic polymerization was also achieved with 1-pentyne. Subsequent hydrogenation yielded 10 g of cyclic poly(1-pentene). Measurements of initial rates during the polymerization of 1-pentyne reveal a catalyst activity of 180,000,000 g/molcat/h.

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Section: ■ Results and Discussionmentioning

confidence: 99%

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confidence: 99%

Cyclic Poly(4-methyl-1-pentene): Efficient Catalytic Synthesis of a Transparent Cyclic Polymer

et al. 2020

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“…1 Nerea Zaldua, 2,3 Romain Liénard, 2 Thomas Josse, 4 Manuela Zubitur, 1 Agurtzane Mugica, 5 Amaia Iturrospe, 5 Arantxa Arbe, 3 Julien De Winter, 2 Olivier Coulembier*, 1,6 Alejandro J. Müller* Linear Cyclic…”

Section: Table Of Contents (Toc) Graphicunclassified

“…The interest generated in these materials has increased as cyclic structures have unique and improved properties. 1 However, the difficulty in the synthesis of cyclic polymers with high cycling and purification efficiency has led to a lack of understanding of the properties. 1 The crystallization of cyclic polymers is a complex subject that needs more research to understand all the relevant factors involved.…”

Section: Introductionmentioning

confidence: 99%

Influence of Chain Topology (Cyclic versus Linear) on the Nucleation and Isothermal Crystallization of Poly(l-lactide) and Poly(d-lactide)

et al. 2018

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In this paper, ring closure click chemistry methods have been used to produce cyclic c-PLLA and c-PDLA of a number average molecular weight close to 10 kg/mol. The effects of stereochemistry of the polymer chains and their topology on their structure, nucleation and crystallization were studied in detail employing Wide Angle X-ray Scattering (WAXS), Small Angle X-ray Scattering (SAXS), Polarized Light Optical Microscopy (PLOM) and standard and advanced Differential Scanning Calorimetry (DSC). The crystal structures of linear and cyclic PLAs are identical to each other and no differences in superstructural morphology could be detected. Cyclic PLA chains are able to nucleate much faster and to produce a higher number of nuclei in comparison to linear analogues, either upon cooling from the melt or upon heating from the glassy state. In the samples prepared in this work, a small fraction of linear or higher molecular weight cycles was detected (according to SEC analyses). The presence of such "impurities" retards spherulitic growth rates of c-PLAs making them nearly the same as those of l-PLAs. On the other hand, the overall crystallization rate determined by DSC was much larger for c-PLAs, as a consequence of the enhanced nucleation that occurs in cyclic chains. The equilibrium melting temperatures of cyclic chains were determined and found to be 5 ºC higher in comparison with values for l-PLAs. This result is a consequence of the lower entropy of cyclic chains in the melt. Self-nucleation studies demonstrated that c-PLAs have a shorter crystalline memory than linear analogues, as a result of their lower entanglement density. Successive selfnucleation and annealing (SSA) experiments reveal the remarkable ability of cyclic molecules to thicken, even to the point of crystallization with extended collapsed ring conformations. In general terms, stereochemistry had less influence on the results obtained in comparison with the dominating effect of chain topology.

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“…The field of macrocyclic polymers has grown significantly in the last decade, thanks to the unique physical properties of these topologies attributed to the lack of end groups, which include reduced melt viscosity, , reduced entanglement, , and increased glass transition temperature at medium-low molecular weight. − One of the more significant practical obstacles in the study of these structures is the presence of a significant quantity of noncyclic impurities in many macrocyclic polymer products . In a previous study, we addressed this issue by providing a promising method for effecting the isolation of linear chains from cyclic oligomers. , The proposed method was exclusively based on the distinct intercalation kinetics of cyclic and linear pentaethylene oxide into the interlayer space of graphite oxide (GO) in both the melt and in solution .…”

Section: Introductionmentioning

confidence: 99%

Poly(ethylene oxide) Melt Intercalation in Graphite Oxide: Sensitivity to Topology, Cyclic versus Linear Chains

2019

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The role of poly(ethylene oxide) (PEO) topology in the melt intercalation in graphite oxide (GO)based materials is investigated. The intercalation of PEO in GO leads to changes in the GO interlayer space and to the suppression of polymer thermal transitions (crystallization and glass transition). Herein, we perform kinetic measurements of the melt intercalation of cyclic and linear PEO (CPEO and LPEO) with M n = 2−20 kg/mol in different GO-based structures by monitoring the reduction of melting peak areas of PEO. We demonstrate that high sensitivity to PEO topology can be achieved using GO partially pillared with 1,6-hexanediamine. Using only 1 wt % of pillars, the rate constants of cyclic PEO become up to a 100 times smaller than that of linear chains of similar molecular weight. This enormous difference in the intercalation kinetics of topologically different PEO chains cannot be achieved in nonpillared GO, where the rate constants of cyclic PEO presented values that were only up to 4 times smaller than that of their linear analogues. The dramatic reduction in the intercalation rate for CPEO in the presence of pillars indicates that topological constraints (formation of squeezed structures with double folded strand conformations) are the most important factors affecting the melt intercalation kinetics. The results suggest that it is possible to restrict the intercalation of cyclic PEO into partially pillared GO, whilst allowing the linear analogue to diffuse through the GO interlayer space. This important finding could be the basis for developing new methods of purification of cyclic polymers.

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Ring Polymers: Effective Isolation and Unique Properties

Cited by 7 publications

References 166 publications

Cyclic Poly(4-methyl-1-pentene): Efficient Catalytic Synthesis of a Transparent Cyclic Polymer

Cyclic Poly(4-methyl-1-pentene): Efficient Catalytic Synthesis of a Transparent Cyclic Polymer

Influence of Chain Topology (Cyclic versus Linear) on the Nucleation and Isothermal Crystallization of Poly(l-lactide) and Poly(d-lactide)

Poly(ethylene oxide) Melt Intercalation in Graphite Oxide: Sensitivity to Topology, Cyclic versus Linear Chains

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