Free-Radical Ring-Opening Polymerization of Macrocyclic Aryl Ether Thioether Ketone Oligomers

Wang, Yifeng; Chan, Kwok P.; Hay, Allan S.

doi:10.1021/ma9517409

Cited by 33 publications

(34 citation statements)

References 18 publications

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“…An interesting diaryl ether (Scheme ) was reported in 1996 by Hay and co‐workers 54. The macrocycle was prepared by the formation of the diaryl ether bond from di(4‐hydroxybenzol)sulfide ( 20 ) and 1,2‐bis(4‐fluorobenzoyl)‐3,6‐diphenylbenzene ( 21 ) under high dilution.…”

Section: Equilibrium (Dynamic) Polymerizationsmentioning

confidence: 99%

Dynamic Covalent Chemistry

Rowan,

Cantrill,

Cousins

et al. 2002

Angew. Chem. Int. Ed.

2,426

1,334

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Dynamic covalent chemistry relates to chemical reactions carried out reversibly under conditions of equilibrium control. The reversible nature of the reactions introduces the prospects of “error checking” and “proof‐reading” into synthetic processes where dynamic covalent chemistry operates. Since the formation of products occurs under thermodynamic control, product distributions depend only on the relative stabilities of the final products. In kinetically controlled reactions, however, it is the free energy differences between the transition states leading to the products that determines their relative proportions. Supramolecular chemistry has had a huge impact on synthesis at two levels: one is noncovalent synthesis, or strict self‐assembly, and the other is supramolecular assistance to molecular synthesis, also referred to as self‐assembly followed by covalent modification. Noncovalent synthesis has given us access to finite supermolecules and infinite supramolecular arrays. Supramolecular assistance to covalent synthesis has been exploited in the construction of more‐complex systems, such as interlocked molecular compounds (for example, catenanes and rotaxanes) as well as container molecules (molecular capsules). The appealing prospect of also synthesizing these types of compounds with complex molecular architectures using reversible covalent bond forming chemistry has led to the development of dynamic covalent chemistry. Historically, dynamic covalent chemistry has played a central role in the development of conformational analysis by opening up the possibility to be able to equilibrate configurational isomers, sometimes with base (for example, esters) and sometimes with acid (for example, acetals). These stereochemical “balancing acts” revealed another major advantage that dynamic covalent chemistry offers the chemist, which is not so easily accessible in the kinetically controlled regime: the ability to re‐adjust the product distribution of a reaction, even once the initial products have been formed, by changing the reaction's environment (for example, concentration, temperature, presence or absence of a template). This highly transparent, yet tremendously subtle, characteristic of dynamic covalent chemistry has led to key discoveries in polymer chemistry. In this review, some recent examples where dynamic covalent chemistry has been demonstrated are shown to emphasise the basic concepts of this area of science.

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Section: Equilibrium (Dynamic) Polymerizationsmentioning

confidence: 99%

Dynamic Covalent Chemistry

Rowan,

Cantrill,

Cousins

et al. 2002

Angew. Chem. Int. Ed.

2,426

1,334

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“…(2), an ipso substitution of aryl iodide by arylthiyl radical produces an unsymmetrical diaryl sulfide and an iodine radical, which is converted to I 2 . 13,16 Similar ipso substitution of a diaryl thioether moiety by arylthiyl radical was proposed in the radical ring-opening polymerizations of macrocyclic aryl ether thioether ketone oligomers and related cyclic oligomers where arylthiyl radicals are expelled: [17][18][19][20] ArOSSOAr O ¡ As described earlier, both nitrobenzene and p-chloronitrobenzene gave diphenyl sulfide in the reaction with diphenyl disulfide, and diphenyl sulfide was likewise formed even in the absence of nitrobenzene. These findings exclude the formation of diphenyl sul-fide by the ipso substitution of nitrobenzene by the phenylthiyl radical.…”

Section: Table IV Molecular Weights Of Thf-soluble Fractions Of Ab Comentioning

confidence: 65%

Devulcanization of nitrile butadiene rubber in nitrobenzene

Masaki

Ohkawara

Hirano

et al. 2004

J of Applied Polymer Sci

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Sulfur-crosslinked nitrile butadiene rubber (s-NBR) was found to be devulcanized when it was heated with nitrobenzene at 200°C for 3 h. The tetrahydrofuran (THF)-soluble fraction from s-NBR heated with nitrobenzene was purified by reprecipitation with THF/n-hexane, chloroform/ n-hexane, and THF/n-hexane systems and was then characterized by means of Fourier transform infrared (FTIR) spectroscopy, 1 H-NMR, gel permeation chromatography, dynamic thermogravimetry/differential thermal analysis (DTA), and differential scanning calorimetry (DSC). FTIR and 1 H-NMR results revealed that the THF-soluble fraction contained aromatic rings derived from nitrobenzene. Furthermore, the molecular weight of the THF-soluble fraction was much lower than that of the parent noncrosslinked poly(acrylonitrile-cobutadiene). Although the weight loss of THF-soluble fraction began at a lower temperature than that of the nonheated original nitrile butadiene rubber, the residual weight at 700°C tended to be higher for the former. This tendency became more marked with increasing time of heat treatment with nitrobenzene. The DSC-determined glass-transition temperature of the THF-soluble fraction was higher than that of the original s-NBR. To elucidate the devulcanization mechanism, we investigated two types of model reactions; one was the reaction of diphenyl disulfide with nitrobenzene, and the other was the reaction of polybutadiene with nitrobenzene. The former reaction, carried out at 250°C in diphenyl ether, yielded diphenyl sulfide with a loss of diphenyl disulfide and nitrobenzene. The use of a higher molar ratio of nitrobenzene to diphenyl disulfide resulted in a depression of diphenyl sulfide formation. The reaction of p-chloronitrobenzene with diphenyl disulfide also gave diphenyl sulfide. The reaction of polybutadiene with nitrobenzene at 200°C resulted in the backbone scission of the polymer. The THF-soluble solid product of the latter model reaction was found by FTIR and 1 H-NMR to contain aromatic rings derived from nitrobenzene. The devulcanization mechanism is discussed on the basis of a comparison of the results of the model reactions with those of the s-NBR devulcanization.

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“…That is, these polymerizations of the macrocycles can be conducted without solvents, and nonvolatile byproducts are liberated during the polymerizations. The ring‐opening polymerization of macrocyclic aryl ether thioether ketones in the melt was reported by Hay et al3 Recently, the ring‐opening polymerizations of aromatic macrocyclic oligomers such as esters,4 aryl ethers,5 and amides6 have also been reported.…”

Section: Methodsmentioning

confidence: 82%

Novel solid-phase polymerization of macrocyclicS-aryl thioesters

Kameyama

Kimura

Nishikubo

2001

J. Polym. Sci. A Polym. Chem.

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The thermal polymerization of macrocyclic S‐aryl thioesters, trimer (m‐CTE‐3), tetramer (m‐CTE‐4), and pentamer (m‐CTE‐5) was investigated. The polymerization of m‐CTE‐3 without a catalyst proceeded efficiently at 280 °C for 10 min in the solid phase to provide poly(S‐aryl thioester) with a weight‐average molecular weight of 1,100,000. Moreover, the solid‐phase polymerization of m‐CTE‐3 proceeded with increasing crystallinity and molecular weight.

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Free-Radical Ring-Opening Polymerization of Macrocyclic Aryl Ether Thioether Ketone Oligomers

Cited by 33 publications

References 18 publications

Dynamic Covalent Chemistry

Dynamic Covalent Chemistry

Devulcanization of nitrile butadiene rubber in nitrobenzene

Novel solid-phase polymerization of macrocyclicS-aryl thioesters

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