Abstract:Low molar mass poly( 2,6-dimethyl-1 ,Cphenylene-ether)^ (PPE) have been prepared by the precipitation polymerization of 2,6-dimethylphenol (DMP ) under the action of a Cu( I )Cl/amine-catalyst and 02. The polymers prepared possess a rather narrow molecular weight distribution (D = 1.7-2.2), and the molecular weight can easily be controlled by adjusting the solvent mixture of 2-propanol and toluene. Molecular weights were determined using 'H-NMR spectroscopy, GPC, and FD-MS, and range from M, = 2700 to 7500 g/m… Show more
“…Besides them, four small peaks were seen at δ 7.1, 6.4, 2.2, and 2.0 due to protons of the α,ω-terminal units (for detailed assignment of peaks, see Experimental Section) . The 13 C NMR spectrum exhibits five main peaks ascribed to carbons of the 2,6-dimethyl-1,4-oxyphenylene unit as well as eight small characteristic peaks, which are well assigned to the terminal units …”
Enzymatic oxidative polymerization of 2,6-dimethylphenol has been
carried out in an
aqueous organic solvent at room temperature under air. Laccase
derived from Pycnoporus coccineous
and horseradish and soybean peroxidases were active for the
polymerization, yielding polymeric materials
with molecular weights of several thousands. The product polymer
was in all cases soluble in common
organic solvents. The polymerization behavior was dependent on the
enzyme type. The effects of the
solvent composition have been systematically investigated with respect
to the polymer yield and molecular
weight. The mixing ratio between the organic solvent and buffer
affected the polymer yield, and the
highest yield was achieved in 60% buffer. Various water-miscible
organic solvents such as acetone,
methanol, and 1,4-dioxane were available as components of the mixed
solvent. In using laccase catalyst,
the acidic buffer afforded the polymer in high yields. NMR and
matrix-assisted laser desorption/ionization
time of flight mass spectroscopic analyses showed that the present
polymer was exclusively composed of
2,6-dimethyl-1,4-oxyphenylene units.
“…Besides them, four small peaks were seen at δ 7.1, 6.4, 2.2, and 2.0 due to protons of the α,ω-terminal units (for detailed assignment of peaks, see Experimental Section) . The 13 C NMR spectrum exhibits five main peaks ascribed to carbons of the 2,6-dimethyl-1,4-oxyphenylene unit as well as eight small characteristic peaks, which are well assigned to the terminal units …”
Enzymatic oxidative polymerization of 2,6-dimethylphenol has been
carried out in an
aqueous organic solvent at room temperature under air. Laccase
derived from Pycnoporus coccineous
and horseradish and soybean peroxidases were active for the
polymerization, yielding polymeric materials
with molecular weights of several thousands. The product polymer
was in all cases soluble in common
organic solvents. The polymerization behavior was dependent on the
enzyme type. The effects of the
solvent composition have been systematically investigated with respect
to the polymer yield and molecular
weight. The mixing ratio between the organic solvent and buffer
affected the polymer yield, and the
highest yield was achieved in 60% buffer. Various water-miscible
organic solvents such as acetone,
methanol, and 1,4-dioxane were available as components of the mixed
solvent. In using laccase catalyst,
the acidic buffer afforded the polymer in high yields. NMR and
matrix-assisted laser desorption/ionization
time of flight mass spectroscopic analyses showed that the present
polymer was exclusively composed of
2,6-dimethyl-1,4-oxyphenylene units.
“…of 2,4-DMP and 6% mol. of 2,4,6-TMP, whereas 2,4,6-TMP can be useful as chain stopper during polymerization of 2,6-DMP [45,46]. Irrespective of the direction of optimization, the final, optimal point of the reactor operation will always be located on the designated operating isoline Φ = 1.Figure 13
Phenol conversion as a function of the bed temperature and o-cresol
in
/phenol
in
ratio during experiments with varying amounts of o-cresol in the feed.…”
Section: Discussionmentioning
confidence: 99%
“…of 2,4-DMP and 6% mol. of 2,4,6-TMP, whereas 2,4,6-TMP can be useful as chain stopper during polymerization of 2,6-DMP [ 45 , 46 ]. Irrespective of the direction of optimization, the final, optimal point of the reactor operation will always be located on the designated operating isoline Φ = 1.…”
Background2,6-dimethylphenol (2,6-DMP) is a product of phenol methylation, especially important for the plastics industry. The process of phenol methylation in the gas phase is strongly exothermic. In order to ensure good temperature equalization in the catalyst bed, the process was carried out using a catalyst in the form of a fluidized bed - in particular, the commercial iron-chromium catalyst TZC-3/1.ResultsSynthesis of 2,6-dimethylphenol from phenol and methanol in fluidized bed of iron-chromium catalyst was carried out and the fluidization of the catalyst was examined. Stable state of fluidized bed of iron-chromium catalyst was achieved. The measured velocities allowed to determine the minimum flow of reactants, ensuring introduction of the catalyst bed in the reactor into the state of fluidization. Due to a high content of o-cresol in products of 2,6-dimethylphenol synthesis, circulation in the technological node was proposed. A series of syntheses with variable amount of o-cresol in the feedstock allowed to determine the parameters of stationary states.ConclusionA stable work of technological node with o-cresol circulation is possible in the temperature range of350-380°C, and o-cresolin/phenolin molar ratio of more than 0.48. Synthesis of 2,6-DMP over the iron-chromium catalyst is characterized by more than 90% degree of phenol conversion. Moreover, the O-alkylation did not occur (which was confirmed by GC-MS analysis). By applying o-cresol circulation in the 2,6-DMP process, selectivity of more than 85% degree of 2,6-DMP was achieved. The participation levels of by-products: 2,4-DMP and 2,4,6-TMP were low. In the optimal conditions based on the highest yield of 2,6-DMP achieved in the technological node applying o-cresol circulation, there are 2%mol. of 2,4-DMP and 6%mol. of 2,4,6-TMP in the final mixture, whereas 2,4,6-TMP can be useful as a chain stopper and polymer’s molar mass regulator during the polymerization of 2,6-DMP.
“…Low molecular weight PPEs were obtained using a precipitation polymerization method. 61 CuCl 99% pure, 4-dimethylaminopyridine (DMAP) 99% pure, 4-oxopentanoic acid 98+% pure, N-methylimidazole 99%, p-toluenesulfonic acid monohydrate 99% pure and a 1 M solution of tetrabutylammonium fluoride (TBAF) in THF were obtained from Acros. 4,4-Bis(4-hydroxyphenyl)pentanoic acid (5a) >98% pure and 4-phenylphenol (1f) >95% pure were obtained from Fluka.…”
Section: Methodsmentioning
confidence: 99%
“…The DMP was recrystallized from n -hexane before use. Low molecular weight PPEs were obtained using a precipitation polymerization method . CuCl 99% pure, 4-dimethylaminopyridine (DMAP) 99% pure, 4-oxopentanoic acid 98+% pure, N -methylimidazole 99%, p -toluenesulfonic acid monohydrate 99% pure and a 1 M solution of tetrabutylammonium fluoride (TBAF) in THF were obtained from Acros.…”
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