Free Volumes and Free Rotation in Simple Liquids and Liquid Saturated Hydrocarbons

Bondì, A.

doi:10.1021/j150521a001

Cited by 202 publications

(85 citation statements)

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“…As expected, the apparent density values for the membranes, determined both by water picnometry and Hg porosimetry ( Another estimation of the FFV of polynorbornene has been made by Bondi's method [22].…”

Section: Densities/pas and Fractional Free Volume (Ffv)supporting

confidence: 61%

Structural characteristics and gas permeation properties of polynorbornenes with retained bicyclic structure

Zhao¹,

Ribeiro²,

Pinho³

et al. 2001

Polymer

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Polynorbornenes of different molecular weights were synthesised by addition polymerisation, using a nickel based catalyst. This polymerisation route leads to amorphous polymers that were shown to display unique properties: high glass transition temperature, rigid random coil conformation, and dense packing in the amorphous state. Gas permeation membranes were prepared from these addition type nonsubstituted polynorbornenes. A study of their gas transport properties was performed and compared with both substituted addition polynorbornenes and ring opening metathesis polymerised polynorbornenes. The observed behaviour, in terms of permeability and selectivity, is in accordance with the low free volume and the dense packing confirmed by positron annihilation spectroscopy and WAXD in these polymer structures. ᭧

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Section: Densities/pas and Fractional Free Volume (Ffv)supporting

confidence: 61%

Structural characteristics and gas permeation properties of polynorbornenes with retained bicyclic structure

Zhao¹,

Ribeiro²,

Pinho³

et al. 2001

Polymer

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“…The midplane density for the 2:2:1 bilayer at 350 K is ∼ 0.7 g/cc 16 , comparable to that of liquid hexadecane ∼ 0.73 g/cc 40 . The excess free energy of water in hexadecane is ∼ 25 kJ/mol 41 , which agrees with the excess chemical potential at the bilayer midplane (Fig.…”

Section: Comparison With Experimentsmentioning

confidence: 81%

Water permeation through stratum corneum lipid bilayers from atomistic simulations

2009

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Stratum corneum, the outermost layer of skin, consists of keratin filled rigid non-viable corneocyte cells surrounded by multilayers of lipids. The lipid layer is responsible for the barrier properties of the skin. We calculate the excess chemical potential and diffusivity of water as a function of depth in lipid bilayers with compositions representative of the stratum corneum using atomistic molecular dynamics simulations. The maximum in the excess free energy of water inside the lipid bilayers is found to be twice that of water in phospholipid bilayers at the same temperature. Permeability, which decreases exponentially with the free energy barrier, is reduced by several orders of magnitude as compared to with phospholipid bilayers. The average time it takes for a water molecule to cross the bilayer is calculated by solving the Smoluchowski equation in presence of the free energy barrier. For a bilayer composed of a 2:2:1 molar ratio of ceramide NS 24:0, cholesterol and free fatty acid 24:0 at 300 K, we estimate the permeability P = 3.7 × 10 −9 cm/s and the average crossing time τ av = 0.69 ms. The permeability is about 30 times smaller than existing experimental results on mammalian skin sections.

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“…carbon tetrachloride solvent ( 18,19). Cyclohexane C6HIZ has V, = 61.4 mL mol-', and hence V, makes a contribution of 47.6 mL mol-' to V and 48.2 mL mol-' to VECl4, i.e.…”

Section: Discussionmentioning

confidence: 99%

Deuterium isotope effects on the partial molal volumes of cyclohexane, acetone, and acetonitrile in carbon tetrachloride

Brown¹,

Edward²,

Edward³

1983

Can. J. Chem.

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At 25°C both molar volumes V and partial molal volumes V: , , , in carbon tetrachloride of cyclohexane-dl? and of acetone-d6 are smallerthan V and V: C14 of the corresponding protio compounds. However, both V and V: , , , of acetonitrile-d, are larger than V and v&.,~ of acetonitrile-h3, and in solvent cyclohexane V:h,,12 of acetone-& and of acetone-h6 are approximately equal.Apparently deuteration has not only a steric effect, but (in polar compounds) a counter-balancing effect, which may be polar.G. RONALD BROWN, JULIAN K. EDWARD et JOHN T. EDWARD. Can. J. Chem. 61, 2684 (1983.A 25"C, les volumes molaires V et les volumesmolaires partiels V: , , , du cyclohexane-dl, et de I'acCtone-d6 dans le tCtrachlorur_e de carbone sont plus faibles que V et v:,,~ des composts non deuttrks correspondants. Cependant, les valeurs de V et de v :~~~ de I'acCtonitrile-d-, sont plusgrandes que les valeurs correspondantes pour I'acCtonitrile non deutCrt; dans le cyclohexane comme solvant, les valeurs de v:,,,,~ de l'acttone-d6 et de I'acttone-h6 sont a peu pres Cgales. Apparemment, la deutCration n'a pas seulement un effet stCrique, mais (dans les composCs polaires) un effet contre balan~ant qui peut &tre polaire.[Traduit par le journal]A large number of examples of secondary deuterium isotope effects on reaction rates (reviewed in refs. 1-3) has been observed. One explanation which accounts for many results depends on the idea that protio-alkyl groups (such as CH,) occupy a slightly larger volume than the corresponding deuteroalkyl groups (such as CD,), because of the greater amplitude of the zero-point vibration of the C-H as compared with the C-D bond. This idea finds support in the studies of Baldry and Robinson (4) on the conformational equilibrium of trans-lmethyl-d,-3-methylcyclohexane, which showed the conformation having CD, axial favoured by 11 cal mol-' over the conformation having CH3 axial; in optical rotatory dispersion studies of Djerassi and co-workers (5); and in studies of steric effects of H and D on ' H and I3C chemical shifts by Anet and Dekmezian (6).However, the most direct indication of this volume difference might be expected to come from measurements of molar volumes. Indeed, at the triple point (7) and at the critical temperature (8) the molar volume V of CH, is greater than that of CD,. Similarly, at ordinary temperatures the molar volumes of benzene (9-1 l ) , cyclohexane (16), and toluene (1 1) are greater than the volumes of their deuterated forms. However, Rabinovich (1 1) repcrted that the molar volumes of CDCl3, CD3N02, PhND?, C H 3 0 D , CH3CH20D, CH,CH2CH20D, (CH3)?CHOD, CH3CH2CH2CH20D, CH20D-CH20D, CH20D-CHOD-CH20D, and (CH,),CCO,D were greater than the volumes of the corresponding protio compounds.This last result pointed to a curious difference between hydrocarbons and more polar organic molecules which we thought worth confirming, particularly since it was based on density measurements made with pyknometers, which are probably less accurate than the direct-reading density meters now availabl...

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Free Volumes and Free Rotation in Simple Liquids and Liquid Saturated Hydrocarbons

Cited by 202 publications

References 0 publications

Structural characteristics and gas permeation properties of polynorbornenes with retained bicyclic structure

Structural characteristics and gas permeation properties of polynorbornenes with retained bicyclic structure

Water permeation through stratum corneum lipid bilayers from atomistic simulations

Deuterium isotope effects on the partial molal volumes of cyclohexane, acetone, and acetonitrile in carbon tetrachloride

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