Local density augmentation from fluorescence lifetime for anthracene N,N-dimethylaniline exciplex in supercritical carbon dioxide

Aizawa, Takafumi; Ikushima, Yutaka; Saitoh, Norio; Arai, Kunio; Smith, Richard L.

doi:10.1016/s0009-2614(02)00526-2

Cited by 10 publications

(9 citation statements)

References 21 publications

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“…In other words, higher pressures would lead to higher concentrations of CO 2 and higher local concentrations. Especially in the supercritical region, local density enhancement has been observed around solvated species by Wada et al28 or around excited complexes, which was clearly shown to have dramatic effects on reaction rates by Aizawa et al29 The incorporation of more CO 2 molecules into the polymer chain would lead to a less stable product that would be easily decomposed at atmospheric conditions or in the presence of water. Super and Beckman30 discussed some of these factors in their review on copolymerizations with CO 2 .…”

Section: Resultsmentioning

confidence: 99%

Copolymerization of carbon dioxide and ethyl vinyl ether at subcritical and supercritical conditions

Yokoyama¹,

Kawase²,

Shibasaki‐Kitakawa³

et al. 2003

J of Applied Polymer Sci

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ABSTRACT:The copolymerization of carbon dioxide (CO 2 ) and ethyl vinyl ether (EVE) at subcritical and supercritical conditions was studied in the presence and absence of an aluminum triacetylacetonate [Al(acac) 3 ] catalyst. The experiments took place at 313-423 K and 4 -15 MPa and for reaction times of 12-120 h. We confirmed that CO 2 could copolymerize with EVE with or without the Al(acac) 3 catalyst, regardless of whether the vessel wall material was Teflon or stainless steel. With the Al(acac) 3 catalyst, a maximum yield of 3.2% polymer was obtained at 338 K, 6 MPa, and 45 h. The maximum value of the average CO 2 fraction was about 50% (100% of the theoretical) at 338 K, 15 MPa, and 45 h. Results confirmed the mechanism and pathways proposed earlier by Soga et al. (1973). There was a trade-off between yield and the CO 2 fraction incorporated into the polymer as conditions changed from subcritical to supercritical.

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Section: Resultsmentioning

confidence: 99%

Copolymerization of carbon dioxide and ethyl vinyl ether at subcritical and supercritical conditions

Yokoyama¹,

Kawase²,

Shibasaki‐Kitakawa³

et al. 2003

J of Applied Polymer Sci

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“…The procedure for estimating the local density was referred to in previous studies. [21][22][23][24][25][26][27][31][32][33][34][35] In this work, the equation expressing the spectral shift is determined by fitting the density of water and the experimentally observed frequencies under conditions where the local density can be regarded as the same as the bulk density. The effect of the solvent polarity on the spectral shift has been expressed by the physical properties of the solvent, which are ε and n, as theoretical equations in previous reports.…”

Section: Estimation Of the Local Density Around Pyridazinementioning

confidence: 99%

Estimation of Local Density Augmentation and Hydrogen Bonding between Pyridazine and Water under Sub- and Supercritical Conditions Using UV-Vis Spectroscopy

et al. 2006

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Various chemical reactions using supercritical fluids have been investigated as a breakthrough that reduces environmental problems. Especially, water (Tc = 374˚C, Pc = 22.1 MPa, and ρc = 0.323 g cm -3 ) is well known as an environmentally benign solvent, and it has been reported that the various inorganic and organic reactions, such as the synthesis of metal oxide nanoparticles, 1-3 the dehydration of alcohols, 4-6 the hydrolysis of ethers, 4,5,7,8 Friedel-Crafts alkylation 9 and the acylation 10 of aromatics occur without a catalyst in supercritical water. These reactions are expected to be controlled by the temperature and pressure (or density), 11,12 since drastic changes in the solvent properties, especially the polarity 13,14 and hydrogen-bonding ability 15 of solvents, cause changes in chemical potential of the reactants, intermediates and products, and thus the activation energy. The solvent properties, which influence the reactions, are mainly the local level around the solute. Therefore, it is necessary to understand the local solvent properties around the solute, especially near to the critical region, in which the local density is different from the bulk. In addition, the hydrogenbonding ability of the solvent also has an influence on the reaction. 42 In the case of nucleophilic reactions, because the nucleophilic species are hydrated by solvent molecules, the reaction rate decreases along with an increase in the hydrogen bonding ability of the solvent. 42 However, hydrogen bonding between the solute and solvent molecules in supercritical water has not yet been clarified.UV-vis spectroscopy has been used to estimate the hydrogen bonding through the spectral shift of a probe molecule. [45][46][47][48] The frequency of the maximum absorbance, νmax, can be empirically represented by the Kamlet-Taft equation 42-48 based on linear solvation energy relationships (LSER), as follows:where the first term, A, is the frequency of the maximum absorbance under the condition with no solvent effect, such as in a gaseous state or a vacuum. The second term, sπ*, is for interactions between the solute and solvent polarities. The third term, aα, and fourth term, bβ, are for interactions between the hydrogen-bond acceptor ability (HBA) of the solute and the hydrogen-bond donor ability (HBD) of the solvent and the interactions between HBD of the solute and HBA of the solvent, respectively. The solvent parameters (π*, α, and β), which are obtained from the spectral shift, have found widespread use in describing many solvation effects observed for physicochemical properties, such as rate constants and equilibrium constants based on LSER. 42-48In addition, the spectral shift under conditions without the effect of hydrogen bonding can be theoretically expressed by the physical properties of the solvent, which are the refractive The local density around pyridazine was evaluated by examining the UV-vis spectral shift of pyridazine in a highpressure liquid state and supercritical water from 25 to 450˚C and from 20 to 45 MPa. Au...

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“…Local density augmentation in near-critical region of fluids has attracted much attention since its elucidation in the late 1980s [1,2] and as a phenomenon specific to the solvent state [3][4][5][6][7][8][9]. It has been investigated by spectroscopic methods such as UV/Vis absorption [3], fluorescence [4], NMR [5], and EPR [6].…”

Section: Introductionmentioning

confidence: 99%

“…We have reported on the local density augmentation around exciplex in supercritical carbon dioxide (SC-CO 2 ) by lifetime analysis of exciplex [7,8]. The acetophenone (AP) N,N,N ,N -tetramethylbenzidine (TMB) exciplex has been investigated by a transient absorption technique [7], and anthracene and N,N-dimethylaniline has been investigated by fluorescence lifetime analysis [8] at 40 • C. Bis(acetylacetonato)beryllium(II) in carbon dioxide has been investigated by Umecky et al [9], who found that the local density augmentation was temperature dependent.…”

Section: Introductionmentioning

confidence: 99%

“…The acetophenone (AP) N,N,N ,N -tetramethylbenzidine (TMB) exciplex has been investigated by a transient absorption technique [7], and anthracene and N,N-dimethylaniline has been investigated by fluorescence lifetime analysis [8] at 40 • C. Bis(acetylacetonato)beryllium(II) in carbon dioxide has been investigated by Umecky et al [9], who found that the local density augmentation was temperature dependent. Local density augmentation around short-lived species might also be expected to show similar behavior, but this topic has not been reported in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Temperature dependence of local density augmentation around exciplex in supercritical carbon dioxide

Aizawa

Kanakubo

Ikushima

et al. 2004

Fluid Phase Equilibria

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Local density augmentation from fluorescence lifetime for anthracene N,N-dimethylaniline exciplex in supercritical carbon dioxide

Cited by 10 publications

References 21 publications

Copolymerization of carbon dioxide and ethyl vinyl ether at subcritical and supercritical conditions

Copolymerization of carbon dioxide and ethyl vinyl ether at subcritical and supercritical conditions

Estimation of Local Density Augmentation and Hydrogen Bonding between Pyridazine and Water under Sub- and Supercritical Conditions Using UV-Vis Spectroscopy

Temperature dependence of local density augmentation around exciplex in supercritical carbon dioxide

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