Macrocyclic Oligomers Research Articles

Cyclic oligomers of poly(ether ketone) (PEK): synthesis, extraction from polymer, fractionation, and characterisation of the cyclic trimer, tetramer and pentamer

Exhaustive extraction of poly(ether ketone) (PEK) with hot chloroform affords a novel range of cyclic oligo(ether ketone)s. The proportion of cyclic material extracted in this way ranged from as high as 13% for laboratory-synthesised PEK to as low as 2% for an industrial development-grade polymer. Extracts were characterised by 1H NMR spectroscopy, GPC, and MALDI-TOF mass spectrometry, which indicated the presence of ring sizes from the cyclic trimer up to at least the cyclic decamer. These macrocyclic oligomers were also prepared (in ca. 80% total yield) by self-polycondensation of 4-fluoro-4′-hydroxybenzophenone under pseudo-high-dilution conditions. Column chromatography on silica gel enabled isolation of the cyclic trimer, cyclic tetramer and cyclic pentamer as pure compounds, characterised by NMR spectroscopy, mass spectrometry, elemental analysis and (for the cyclic trimer and cyclic tetramer) X-ray crystallography. Ring-opening polymerisation of mixed cyclic oligomers was achieved in the melt at 385 °C, using the potassium salt of 4-hydroxybenzophenone as initiator.

Poly(aryl ether)s containingo-terphenyl subunits. II. Random poly(ether sulfone)s

The synthesis of new A 2 X-type difluoride monomer, N-2-pyridyl-4',4-bis-(4-fluorobenzenesulfonyl)-o-terphenyl-3,6-dimethyl-4,5-dicarboxylic imide (3), is described. The monomer 3 was incorporated into a series of copoly(aryl ether sulfone)s by polymerization of 4,4'-isopropylidenediphenol and 4,4'-difluorophenylsulfone. The incorporation of monomer 3 had an observable effect on both the glass-transition temperature of poly(aryl ether sulfone)s and the tendency for macrocyclic oligomers to form during polymerization. Replacement of the pyridyl imide group via a transimidization reaction with propargyl amine proceeded quantitatively and without polymer degradation. The acetylene containing copoly(aryl ether sulfone) could be crosslinked by simple thermal treatment, resulting in an increase in the glass-transition temperature and solvent resistance.

Macrocyclic oligomers of the aromatic polyetherketone “PK99”: synthesis, fractionation, structural characterisation and ring-opening polymerisation

Cyclo-condensation of 4,4′-dihydroxybiphenyl with 1,3-bis(4-fluorobenzoyl)benzene under conditions of pseudo-high dilution affords a new series of macrocyclic ether-ketone oligomers. A number of these (the cyclic [2 + 2] dimer, [3 + 3] trimer, and [5 + 5] pentamer) have been isolated chromatographically as pure compounds. The odd-numbered macrocycles are readily-soluble, non-crystalline glasses, but the cyclic dimer is crystalline, high-melting (403 °C) and relatively insoluble. Its structure, determined by single-crystal X-ray methods, provides a new model for chain-folding within lamellar crystallites of aromatic polyketones. The [4 + 4] cyclic tetramer, although detectable by MALDI-TOF MS, appears to be so insoluble that it cannot be extracted from the product mixture. The amorphous cyclic trimer undergoes ring-opening polymerisation at 300 °C in the presence of a fluoride initiator, to give tough, semi-crystalline polymer.

Novel macrocyclic aryl thioether ester oligomers: structure characterization and free-radical ring opening polymerization

Novel macrocyclic aryl thioether ester oligomers have been synthesized in high yield from phthaloyl dichloride and 4,4′-thiodiphenol under pseudo high dilution conditions. The cyclic nature was unambiguously confirmed by a combination of MALDI-TOF MS, gel permeation chromatography and NMR analyses. Single-crystal X-ray diffraction of cyclic ester dimer reveals no severe strain on the cyclic structure. The free-radical ring opening polymerization (ROP) of the macrocyclic oligomers was achieved to give high molecular weight polymers via a transthioetherification reaction. The molecular weight of the polymer resulting from ROP decreases as the conversion of cyclic oligomers increases after a polymerization period of 30 min.

Novel macrocyclic aryl thioether ester oligomers: structure characterization and free-radical ring opening polymerization

Novel macrocyclic aryl thioether ester oligomers have been synthesized in high yield from phthaloyl dichloride and 4,4'-thiodiphenol under pseudo high dilution conditions. The cyclic nature was unambiguously confirmed by a combination of MALDI-TOF MS, gel permeation chromatography and NMR analyses. Single-crystal X-ray diffraction of cyclic ester dimer reveals no severe strain on the cyclic structure. The free-radical ring opening polymerization (ROP) of the macrocyclic oligomers was achieved to give high molecular weight polymers via a transthioetherification reaction. The molecular weight of the polymer resulting from ROP decreases as the conversion of cyclic oligomers increases after a polymerization period of 30 min.

Synthesis and polymerization of some macrocyclic (arylene ether sulfone) containing cardo groups and macrocyclic (arylene ether ketone sulfone) oligomers

Some novel macrocyclic (arylene ether sulfone) containing cardo groups and (arylene ether ketone sulfone) oligomers have been synthesized in high yields by a nucleophilic aromatic substitution reaction of 4,4′-difluorophenylsulfone with bisphenols in the presence of anhydrous potassium carbonate under a pseudo-high-dilution condition. Detailed structural characterization of these oligomers by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS), fast atom bombardment mass spectrometry (f.a.b.-m.s.), nuclear magnetic resonance spectrometry (n.m.r.) and single-crystal X-ray structure analysis confirms their cyclic nature, and the composition of the oligomeric mixtures is provided by g.p.c. analysis. Ring-polymerization of cyclic oligomers 3a to a high molecular weight polymer with M w of 59.1 k was achieved by heating at 290°C for 40 min in the presence of a nucleophilic initiator.

Absolute configuration of the polyazamacrolides, macrocyclic polyamines produced by a ladybird beetle

The absolute configuration of the polyazamacrolides, oligomeric macrocycles from the pupal defensive secretion of Epilachna borealis, was determined by comparison of derivatives of the natural material with enantiomerically pure synthetic samples. Samples of a mixture of three (ω-1)-(2-hydroxy-ethylamino)alkanoic acids and of the corresponding aza-lactones were synthesized from (R)-malanimol. Gas chromatographic comparison of MTPA-amides of the synthetic aza-lactones with the MTPA-amides of aza-lactones prepared from the natural material established that the polyazamacrolides have the (R)-configuration at all stereogenic centers.

Use of calixarene compounds as selectivity modifiers in capillary electrophoresis separations

The use of calixarene compounds as selectivity modifiers and potassium bromide as electrolyte in capillary electrophoresis (CE) was studied. Calixarenes are macrocyclic oligomers having the shape of a conical vase whose inner cavity can accommodate various guest molecules. These compounds absorb in the ultraviolet region, with maxima at approximately 204 nm, and can be employed for the indirect determination of various types of compounds. The use of water soluble sulphonated calixarene as mobile phase in combination with different salts allowed us to develop electrophoretic methods for the determination of special compounds which are transparent in the UV region. The potential of this buffer was assessed by separating various groups of analytes including amino acids, biogenic amines and inorganic cations and anions. A system consisting of seven amino acids, used as model compounds, was chosen to optimize the buffer. The different instrumental variables affecting sensitivity and resolution of the mixture were carefully optimized.

ChemInform Abstract: Acid‐Catalyzed Rearrangements Between 3,4‐Dihydro‐2H‐1,5‐benzooxazocine and ‐benzothiazocine and Their Macrocyclic (16‐Membered, 24‐Membered, and 32‐Membered) Oligomers.

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Acid-catalysed rearrangements between 3,4-dihydro-2H-1,5-benzooxazocine and -benzothiazocine and their macrocyclic (16-membered, 24-membered and 32-membered) oligomers

Treatment of 2-(3-azidopropoxy)benzaldehyde with triphenylphosphine in diethyl ether, followed by sequestration of the products with nickel(II) thiocyanate and subsequent liberation from the complex with aqueous ammonia, produces the 16-membered dimer of 3,4-dihydro-2H-1,5-benzooxazocine. The dioxadiaza diimine macrocycle 3 undergoes an acid-catalysed rearrangement in solution into an equilibrium mixture that includes the trioxatriaza triimine (24-membered) 8 and tetraoxatetraaza tetraimine (32-membered) 9 macrocycles, as well as the diimine. The oligomers in [2H]chloroform differ in the 1H NMR chemical shifts of the protons on the central carbon atoms of the propane-1,3-diyl links, thereby allowing an investigation of the factors involved in the rearrangements between the macrocyclic oligomers. Thus, the rearrangements of the macrocyclic polyimines into equilibrium mixtures of the various oligomers occurs with t>>½>> 7–10 min, but the position of the equilibrium in each case is dependent upon the imine equivalent concentration of the solution. 3,4-Dihydro-2H-1,5-benzothiazocine undergoes a similar rearrangement. The equilibrations have been ascribed to facile intermolecular transiminations between the oligomers in the presence of traces of acid and to the similarities of the thermodynamic stabilities of the 16-, 24- and 32-membered oligomers. The crystal and molecular structures of ammonium nitrate salts of the 16-membered diamine 11 and 32-membered tetraamine 10 derivatives of the corresponding macrocyclic benzooxazocines are reported.

Cyclodepolymerisation of bisphenol A polysulfone: evidence for self-complementarity in macrocyclic poly(ether sulfones)

The engineering thermoplastic generally referred to as ‘bisphenol A polysulfone’ undergoes fluoride-promoted cyclodepolymerisation; high molar mass polymer is thus transformed into a series of macrocyclic oligomers containing up to at least 72 aromatic rings; those containing up to 24 rings have been isolated as pure compounds, and single-crystal X-ray studies of the cyclotrimer and cyclotetramer reveal shape-complementary pairs and chains of macrocyles, respectively.

New enantiomerically pure oligomeric macrocycles based on a 3,4-dihydroxypyrrolidine nucleus

(3S,4S)-N-Benzyl-3,4-dihydroxypyrrolidine 1 has been used as a building block for new enantiopure macrocyclic polyesters. Two different synthetic approaches are presented leading to complementary results. The structure of the macrocycles synthesized has been confirmed by NMR spectroscopy and FAB mass spectrometry, and that for dimer 8 has been confirmed by X-ray analysis.

Two‐ and Three‐Dimensional Tetrathiafulvalene Macrocycles

AbstractThe syntheses and some physical properties (redox potentials) of cyclic tetrathiafulvalenes (TTF) are reviewed. The ring closure is generally performed in one of two different ways: (i) by coupling of 1,3‐dithiol derivatives thereby forming the central fulvene bond, or (ii) by cyclization of a preformed TTF derivative. The second route is very efficient when using the cyanoethyl protection/deprotection method and has made possible the preparation of a number of two‐ and three‐dimensional macrocycles, e.g. mono‐, bis‐ and tetramacrocycles, oligomeric macrocycles and cage‐type molecules. The use of tetrathiafulvalenophanes in supramolecular chemistry is also exemplified in this microreview.

Efficient synthesis and facile polymerization of some cyclic bisphenol o‐phthalates

AbstractA series of new macrocyclic aromatic esters have been efficiently synthesized from o‐phthaloyl dichloride and various bisphenols, and unambiguously characterized by a combination of GPC, MS(FAB), FTIR and NMR. These macrocyclic oligomers undergo facile ring‐opening polymerization in the presence of anionic initiators to give high molecular weight polyarylates.

Novel macrocyclic aryl ether oligomers containing a diphenylacetylene moiety: synthesis, characterization and ring-opening polymerization

An efficient synthetic route to a range of macrocyclic aryl ether ketone and sulfone oligomers containing a cross-linkable diphenylacetylene moiety in the backbone is described. This new class of macrocyclic oligomers, obtained in excellent yield, is prepared by an aromatic nucleophilic substitution reaction from the potassium salt of bis(3-hydroxyphenyl)acetylene and activated difluoro-monomers. Detailed structural characterization of these novel oligomers by the combination of n.m.r. and matrix assisted laser desorption and ionization-time of flight-mass spectroscopy (MALDI-TOF-MS) confirms their cyclic nature; and the compositions of these macrocyclic oligomers are provided by g.p.c. and reverse-phase gradient h.p.l.c. analyses. MALDI-TOF-MS is a unique tool for the determination and the proof of the cyclic nature of random co-cyclic oligomers, and also provides answers to the possible combinations of monomer units in the cyclic olgiomeric components for the random co-cyclic oligomers. All macrocyclic oligomers are semicrystalline with T m varying from 267 to 370°C and when the oligomers are heated an exothermic reaction, resulting from reaction of the acetylene units, occurs in the range of 340–470°C and the macrocyclics undergo a cross-linking reaction. Polymerization of the lower melting macrocyclic oligomers at 280–300°C, in the presence of a nucleophilic initiator, led to the formation of high molecular weight insoluble materials with limited cross-linking reactions taking place. The resulting polymers can be further cross-linked at 340°C with a T g increase up to 100°C or complete disappearance of T gs.

Thermodynamically-controlled cyclisation and interconversion of oligocholates: metal ion templated ‘living’ macrolactonisation

A series of ester-linked macrocyclic oligomers (dimer–pentamer) of cholates equipped with a variety of recognition and reporter elements has been prepared (a) by conventional irreversible chemistry, and (b) using methoxide-catalysed transesterification under reversible equilibrium conditions. Templating by metal ions under these equilibrium conditions is also demonstrated. These results demonstrate the feasibility of creating a dynamic combinatorial library of receptors.

Macrocyclic oligomers of isophthalic acid and trans-1,2-diaminocyclohexane — building blocks for synthetic peptide receptors

New macrocyclic oligomers of isophthalic acid and trans-1,2- diaminocyclohexane are readily prepared and useful in the synthesis of new, sequence-selective receptors for peptides. Such receptors have a simple, two-armed structural motif and the peptide sequences they bind vary with the ring size of the macrocyclic arms.

Synthesis, characterization, and ring-opening polymerization of novel highTg macrocyclic oligomers based on 1,2-dihydro-4-(4-hydroxyphenyl)(2H)- phthalazin-1-one

Preparation of novel high T g (220-280°C) macrocyclic oligomers in high yield by the reaction of 1,2-dihydro-4- (4-hydroxyphenyl) (2H)phthalazin-1-one with activated difluoro-monomers is described. The reaction, conducted under pseudo-high dilution conditions, produces cyclic oligomers in 90-97% isolated yield. Detailed structural characterization of these novel oligomers by the combination of NMR, MALDI-TOF-MS, GPC, and reverse-phase HPLC confirm the cyclic nature and reveal the composition of these cyclic oligomers. MALDI-TOF-MS which enables the detection of oligomers with mass up to 6000 Da, is shown to be a very powerful tool for determination of and the proof of the cyclic nature of the cyclic oligomers. The MALDI results provide answers to the possible combinations of monomer units in the cyclic oligomeric components for random co-cyclic oligomers. Rheological measurement of cyclic oligomers 3c shows that the cyclic oligomers are thermally stable in the melt and the molten cyclic oligomers essentially behave like Newtonian fluids. At 340°C and 100 s the steady-state shear viscosity of the molten cyclic oligomers 3c is only about 14 poise. Ring-opening polymerization of the co-cyclic oligomers 4 to a high molecular weight polymer with M w = 87,000 is achieved by heating at 340°C for 45 min in the presence of nucleophilic initiator.

Novel aromatic macrocyclic oligomers: intermediates for the preparation of high-performance polymers

Recent studies aimed at the development of macrocyclic oligomers as the intermediates for the preparation of high-performance polymers are reviewed. Efficient methods for the preparation of a range of cyclic oligomers, such as aryl ether ketones, aryl ether phthalazines, aryl ether isoquinolines, aryl ether phthalazinones, and arylene sulfides, have been developed. Cyclization was achieved via a nucleophilic aromatic substitution reaction under high-dilution conditions. The cyclic aryl ether oligomers undergo a facile ring-opening polymerization to form high molecular weight polymer. Cyclic oligomers containing an aromatic sulfide linkage also undergo a facile free-radical ring-opening polymerization to form high molecular weight polymers which can be amorphous or crystalline. Due to their low molecular weights, these cyclic oligomers have very low melt viscosities which makes them attractive intermediates for a variety of applications for which the conventionally prepared high molecular weight polymers would not be suitable.

Analysis of Macrocyclic Polystyrenes. 1. Liquid Chromatographic Investigations

Macrocyclic polystyrenes prepared by a single-step, pseudo-unimolecular cyclization of a linear α-(diethoxyethyl)-ω-styrenylpolystyrene can effectively be analyzed by liquid chromatography at the critical point of adsorption. Using silica gel as the stationary phase and THF−hexane as the eluent, the macrocyclic oligomers are separated from their linear precursors and other nonfunctional linear oligomers. The quantitative determination of the cyclization yield can be carried out via appropriate detector calibration for the linears and cyclics. Additional information on the chemical structure of the linears and cyclics is obtained by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. In conclusion, a possible cyclization mechanism is given including an interpretation of the MALDI behavior of the samples.