Structure of Ammonium/Phenoxide Ion-Pairs in Solution

Menger, Fredric M.; Barthélémy, P.

doi:10.1021/jo951937z

Cited by 4 publications

(1 citation statement)

References 16 publications

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“…Basic amines are known to form phenol‐amine salts with the weakly acidic phenols that are used as co‐catalyst to cure the cyanate esters resins. Furthermore, the phenol‐amine salts exist in the equilibrium state between the amine and the phenol as shown in Scheme 1 15–18 . It indicates that phenol‐amine salts consisting of simple phenols and amines cannot provide storage stability in cyanate ester resins.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the hardener with latent and rapid curing based on phenol‐amine salts for applications to cyanate ester resins

Ueyama

Ogawa²,

Tsuge

et al. 2021

J of Applied Polymer Sci

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We have developed the curing agents that have good storage stability for cyanate ester resins. It should be noted that these agents can be given rapid and efficient curing at low temperatures around 100°C. Even though the nucleophilicity was reduced by a phenol‐amine salts consisting of basic aliphatic amines and weakly acidic phenols, the curing reaction with the cyanate ester occurred immediately. It means that the control of the curing reaction with cyanate esters is not easy due to the equilibrium between phenol and amine. In order to overcome this difficultly cyanate esters reactivity, the molecular motions suppression by polymer was applied in addition to the phenol‐amine salts. The effect of the suppression for hardeners was studied in terms of the storage stability and reactivity to cyanate esters. It has been found out that PSM‐EPEDA composed of ethylenediamine‐epoxy adducts and novolac phenolic resin exhibits a large storage stability against cyanate esters by its effective suppression of molecular motions accompanied with efficient and rapid curing around 100°C.

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Section: Introductionmentioning

confidence: 99%

Investigation of the hardener with latent and rapid curing based on phenol‐amine salts for applications to cyanate ester resins

Ueyama

Ogawa²,

Tsuge

et al. 2021

J of Applied Polymer Sci

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Hydrogen-bonding-based thermochromic phenol-amine complexes

Mizutani

Takagi

Ueno

et al. 1998

J. Phys. Org. Chem.

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Variable-temperature UV-vis, 13 C NMR and IR studies showed that proton-transferred complexes were formed between phenols and amines in apolar solvents at low temperature. Upon cooling a solution of pnitrophenol and diisopropylamine in toluene, the colour of the solution changed from colourless to yellow. This thermochromism was ascribed to the proton transfer in the hydrogen-bonding complex. Under UV-vis conditions, butylamine and imidazole also caused similar thermochromism upon complexation with p-nitrophenol, while triethylamine, quinuclidine and pyridine did not. The thermochromic behaviour was particularly dependent on the stoichiometry of the amine and the phenol: a solution of 3,3'-dibromo-5,5'-dinitro-2,2'-biphenyldiol and diisopropylamine with a molar ratio of 1:1 showed no thermochromism, while solutions with 1:2 or higher ratios showed thermochromism, indicating that excess amine is required to obtain the proton-transferred species. These results revealed that the proton-transferred species forms in apolar solvents at low temperature if an appropriate hydrogen-bonding network between the phenol and the amine can stabilize it.

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