Multicyclic Polyethers Derived from Tetra(bromomethyl)methane and Flexible Diphenols

Macromol. Rapid Commun.

2007

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Characteristic similarities and differences in polycondensations of ‘a − b’ and ‘a2 + b2’ monomers are described including cyclic ‘a − b’ and cyclic ‘a2’ monomers. Polycondensations of ‘ab3’ monomers that yield (hyper)branched polymers are compared with polycondensations of ‘a2 + b3’ monomers that yield (hyper)branched, multicylic, or crosslinked polymers. In all cases the influence of cyclization reactions on structure and molecular weight of the reaction products is considered. Furthermore, the definitions of polycondensation and condensative chain polymerization are discussed along with a differentiation between kinetically controlled and thermodynamically controlled polycondensations.magnified image

Section: Randomly Branched and Multicyclic Polymersmentioning

confidence: 99%

Polycondensation of ‘a − b_n’ or ‘a₂ + + b_n’ Monomers ‐ A Comparison

Macromol. Rapid Commun.

2007

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“…Ti(OBu) 4 is known as the most efficient catalyst for syntheses of polyesters from alkane diols and dimethylesters of dicarboxylic acids and has been proved in our recent study on comparison of several transesterification catalysts . Therefore, this catalyst is widely used for research activities in the field of polyesters and also for the technical production of poly(butylene terephthalate). – Consequently, the first series of experiments of this work were performed with Ti(OBu) 4 as catalyst (see Table ). In the first four experiments, the catalyst was added once in the beginning of the polycondensation.…”

Section: Resultsmentioning

confidence: 99%

Biodegradable Hyperbranched Aliphatic Polyesters Derived from Pentaerythritol

Behnken

2008

Macromolecules

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Pentaerythritol (PENT) was polycondensed with dimethyl sebacate (DMS) in bulk at 240 °C. With Ti(OBu)4 as the catalyst, an equimolar feed ratio resulted in gelation even when no vacuum was applied. When the PENT/DMS ratio was raised to 1.2/1.0, soluble viscous resins were obtained, but despite the excess of PENT, the conversion of methyl ester groups never exceeded 92%. With bismuth(III) n-hexanoate (BiHex3) as the catalyst and an 1.0/1.0 feed ratio, nonviscous polyesters were obtained with conversions <75%. When BiHex3 was used in the beginning and Ti(OBu)4 was added at a later stage, soluble viscous resins were obtained even at 1.0/1.0 feed ratio. Further polycondensations were conducted with higher PENT/DMS ratios. The reaction products were characterized by viscosity measurements, 1H NMR spectroscopy, and MALDI-TOF mass spectrometry. These measurements indicated the formation of hyperbranched polyesters almost free of cycles and ether groups. Furthermore, acylations with acetic or methacrylic anhydride were studied and quantitative conversions of the CH2OH groups were achieved.

“…In four recent publications, [7][8][9][10] it was demonstrated that this concept is realistic and successful. Furthermore, it should be mentioned that recently Nishikubo and coworkers synthesized a multicyclic oligomer by reversible a 2 þ b 4 polycondensation.…”

Section: Full Papermentioning

confidence: 99%

Multicyclic Poly(ether ester)s by Polycondensation of Ethoxylated Pentaerythritol with Dicarboxylic Acid Dichlorides

Macro Chemistry & Physics

Bornhorst

Schwarz

2007

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Commercial ethoxylated pentaerythritol (EPE) was polycondensed with phthaloyl chloride, isophthaloylchloride, terephthaloyl chloride, and sebacoyl chloride. The monomer concentration was varied to find the borderline between soluble multicylic polyesters and gelation. The tendency of gelation increased in the above given order of dicarboxylic acids. Gelation was also favored by a lower content of ethylene oxide units in the EPE. An alternative approach based on the cyclization of EPEs with dibutyltin dimethoxide followed by acylation with dicarboxylic acid dichloride proved to be unsuccessful. The soluble multicycles were characterized by 1H NMR spectroscopy, MALDI‐TOF mass spectrometry, viscosity, and SEC measurements. The DSC measurements confirmed an amorphous character of all polyesters.magnified image