Abderrazak Ben-Haida

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.

Entropically-driven ring-opening polymerization of macrocyclic esters with up to 84-membered rings catalysed by polymer-supported Candida antarctica lipase B

Macrocyclic esters with 24- to 84-ring atoms can be polymerized successfully using PS Candida antarctica lipase B as the catalyst. This method allows the polymerization of macrocycles containing substantial in-chain functional moieties, such as monomers incorporating steroid residues. It also affords metal-free products.

Microfabrication of high-performance aromatic polymers as nanotubes or fibrils by in situ ring-opening polymerisation of macrocyclic precursors

Melt-phase nucleophilic ring-opening polymerisation of macrocyclic aromatic ethers and thioethers at high temperatures within the cylindrical pores of an anodic-alumina membrane, followed by dissolution of the template, enables replication of the membranes internal pore structure and so affords high-performance aromatic polymers with well-defined fibrillar or tubular morphologies.

RING-CLOSING DEPOLYMERISATION OF AROMATIC POLYETHERS

Equilibration of aromatic poly(ether sulfone)s and poly(ether ketone)s under conditions of fluoride-catalysed ether exchange leads, at low polymer concentrations in dipolar aprotic solvents, to efficient ring-closing depolymerisation.

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.