Suzuki polycondensation: On catalyst derived phosphorus incorporation and reproducibility of molecular weights

Frahn, Jörg; Karakaya, Birol; Schäfer, Andreas; Schlüter, A. Dieter

doi:10.1016/s0040-4020(97)00973-3

Cited by 43 publications

(35 citation statements)

References 19 publications

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“…Considering the result of entry 3 (Tab. 2), which is typical for SPC of 3 with freshly prepared Pd(PPh 3 ) 4 , it can be concluded that not only for dibromides 7) but also for diiodide 3 P-incorporation is an existent side reaction which is in absolute terms, however, negligible. Roughly only every fourth chain (PS standard) contains one Patom.…”

Section: Resultsmentioning

confidence: 90%

“…Using P n data from GPC referenced to polystyrene standard. Unfortunately we were not able to structurally assign this signal with the help of model compounds 7) . The cross-peaks in NOESY spectra show that P-atoms absorbing at 29.4 ppm have at least one phenyl substituent which may indicate that they are integral parts of the backbone.…”

Section: General Procedures For Polycondensationmentioning

confidence: 99%

“…Novak also found using Pd 2 (dba) 3 with P(o-tolyl) 3 as co-ligand that in this reaction no ligand derived phosphorus incorporation into the backbone takes place. This side reaction was of some concern during the development of SPC with dibromo monomers until it could be shown that the extent to which this happens is negligible for relevant conditions 7) . Since SCC and thus SPC of iodoaromatics proceed at a high rate under especially mild conditions we set out to investigate the potential for SPC of a diiodo monomer and compare it with an otherwise identical monomer differing only in the nature of the halogene leaving group (iodo or bromo).…”

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confidence: 99%

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Improved Suzuki polycondensation: A diiodo versus a dibromo monomer

Schlüter

Frahn

Karakaya

et al. 2000

Macromol. Chem. Phys.

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Section: Resultsmentioning

confidence: 90%

Section: General Procedures For Polycondensationmentioning

confidence: 99%

mentioning

confidence: 99%

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Improved Suzuki polycondensation: A diiodo versus a dibromo monomer

Schlüter

Frahn

Karakaya

et al. 2000

Macromol. Chem. Phys.

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“…However, it is probable that pseudo oligomeric species exist as defects in the backbone conjugation of PFO. Breaks in conjugation would arise close to oxidative defects [18] and in the region of catalyst impurities incorporated or formed during the polymer synthesis [19]. Breaks in conjugation could also be located at chain ends [20] due to increased chain dynamics.…”

Section: Resultsmentioning

confidence: 99%

Energy up-conversion in dilute polyfluorene solutions

et al. 2007

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Poly(9,9-dioctylfluorene) (PFO) shows highly efficient blue emission with photo excitation occurring between 340-400 nm. Here we show that PFO can in dilute solution emit at a wavelength well below that at which it is being exited. This, we propose is related to an energy transfer from conjugated parts of the polymer chain into more localised states which then emit at a lower wavelength. These localised states can be considered as defects in the conjugation of the polymer or as chain ends. These may produce quasi monomer or quasi dimer species within the chain, which will have a HOMO-LUMO gap of higher energy than the conjugated polymer. These then fluoresce at the lower wavelength; essentially causing, by energy transfer, a process of energy up-conversion.

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“…This makes it difficult to meet the required 1 : 1 stoichiometry precisely. Aromatic diboronic acids which are the most commonly used coupling partners for dibromides like 3 d in Suzuki polycondensation contain some water whose content is determined NMR spectroscopically 6) . This water content renders the achievement of the correct stoichiometry even more difficult and it was therefore decided to use ester 4 instead which can be obtained as fine crystalline easy to weigh material which does not contain water.…”

Section: Progress Toward the Polymerization Of A Fourth Generation Dementioning

confidence: 99%

Progress toward the polymerization of a fourth generation dendritic macromonomer

Schlüter²

1999

Macromol. Rapid Commun.

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SUMMARY: The g-scale synthesis of the fourth generation dendronized monomer 3d and its Suzuki oligomerization are reported. The monomer synthesis uses the fact that the addition of two G-3 fragments to aryldibromide 3 c which already contains one branching unit is more practical than an alternative approach by which a G-4 dendron is added to a respective compound. The Suzuki cross-coupling of 3d gives oligomeric material 5, a fraction of which with a molecular weight of M -n = 170 000 is obtained by preparative gel permeation chromatography. This finding shows that the Suzuki cross-coupling reaction can cope with considerable steric loading of coupling components which opens up new perspectives for its applicability both in organic and polymer chemistry.There is increasing interest in the polymerization of monomers with dendritic side chains 1) . The resulting polymers complement the known dendrimers because the dendrons are attached to a polymeric and, thus, polyfunctional core rather than a small and oligofunctional one 2) . Dendrimers with polymeric cores are presently being investigated mainly for their unprecedented mesophase behavior 3) and the idea that some of them may be cylindrically shaped molecular objects on the nanometer scale 4) . A nano object retains the same shape and (nano) dimensions regardless of its environment. This would require the most dense attachment of the largest dendrons to a backbone possible. Ultimately the backbone ought to be surrounded by a layer of dendrons which are tightly packed at van-der-Waals distance. The synthesis of such polymers is prone to all kinds of problems which can be subsumed with the catchword steric hindrance. It is both a challenging goal for polymer synthesis and a critical hurdle for a further development of dendritic molecular objects to investigate the polymerizability of dendronized macromonomers in dependence on the dendron's steric demand (generation). Practically all reported examples use monomers with first and second generation dendrons 1a) . Sometimes spacers are introduced between the dendron and polymerizable groups. A Suzuki-type 4) and a styrene derived macromonomer 5) are the only two cases where third generation macromonomers were successfully polymerized. We report here the synthesis of a fourth generation (G4) Suzuki-type monomer and the results of initial attempts to subject it to a step-growth polymerization.Previously we have reported the synthesis of dendronized monomers for Suzuki polycondensation which were obtained by reacting compound 1 with first, second, and third generation (G1,2,3) Fréchet-type dendrons in a Williamson ether synthesis at the benzylic position 4 a) . The yields of these reactions dropped from 79 to 44% with increasing dendron size. An unfavorable interaction between incoming dendron and the bromo substituent ortho to the benzylic bromide may be responsible for this. For the synthesis of a monomer with appendant G4 dendron this direct route was therefore not considered here but a route was designed instea...

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Suzuki polycondensation: On catalyst derived phosphorus incorporation and reproducibility of molecular weights

Cited by 43 publications

References 19 publications

Improved Suzuki polycondensation: A diiodo versus a dibromo monomer

Improved Suzuki polycondensation: A diiodo versus a dibromo monomer

Energy up-conversion in dilute polyfluorene solutions

Progress toward the polymerization of a fourth generation dendritic macromonomer

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