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- Orädd, Greger, et al.
(författare)
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Diffusion: a comparision between liquid and solid polymer LiTFSI electrolytes
- 2001
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Ingår i: 13th International Conference on Solid State Ionics (8-14 July 2001), Cairns, AUSTRALIA. ; 152-153, s. 131-6
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Konferensbidrag (refereegranskat)abstract
- From careful analyses of pfg-NMR data, it is demonstrated that the size of the diffusing Li+·xH2O complex in an aqueous solution of LiTFSI is strongly dependent on salt concentration, with the number of solvating water units ranging from six in dilute (H2O)500LiTFSI to two in highly concentrated (H2O)5LiTFSI. Such a relationship is explained by a mass tendency toward a lower solvation number as the number of available H2O molecules per lithium ion decreases. In a liquid (PEO)nLiTFSI system, a contrasting situation prevails, since the size of the diffusing Li+ complex is almost constant over a large salt concentration range (5≤n≤50). Our interpretations of these data imply that one PEO chain, containing on average nine ether oxygen units, is able to dissolve up to two lithium ions, but exclude the possibility of cationic crosslinks between different PEO chains and direct ionic interactions. For solid P(EO)nLiTFSI eletrolytes, a significantly lower value for the diffusion coefficient of the small lithium ions as compared to that of the large TFSI ions (DLi=0.2DTFSI) was found for all salt concentrations investigated (5≤n≤50). This observation fits in with recent structural observations, which suggest that lithium ions move as single entities in this specific system and require a rather complicated solvation–desolvation step for long-range motion. In all electrolytes investigated, both liquid and solid, the large and bulky TFSI ion appears to be moving as a single unit, thus manifesting the excellent ionization properties of the LiTFSI salt.
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- Orädd, Greger, et al.
(författare)
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Diffusion and dielectric studies of the system PPO4000–NH4CF3SO3
- 1999
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Ingår i: International Conference(12th) on Solid State Ionics Held in Kassandra, Halkidiki Thessaloniki, Greece on June 6-12, 1999. ; 136-7, s. 457-61
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Konferensbidrag (refereegranskat)abstract
- A polymer electrolyte system composed of poly(propylene oxide) of molecular weight 4000 (PPO4000) complexed with NH4CF3SO3 (NH4TF) has been investigated by multinuclear pfg-NMR and AC impedance methods. Samples in the concentration range 0.03–0.69 mol/kg (O:NH4 ratios of 500:1–22:1) have been investigated over the temperature range 25–75°C. The combination of AC conductance and pfg-NMR diffusion measurements gives clear evidence that extensive ion-aggregation/clustering occurs at low salt concentrations. With increasing salt-content the Haven ratio, defined as Λcalc/Λexp, decreases from >100 to 2 when going from 0.03 to 0.69 mol/kg. Such gross deviations from the Nernst–Einstein relation (i.e. Λ ∝ D++D−) originate in extensively correlated motions of ions. We interpret the results in terms of labile salt-rich sub-domains being further destabilized through an increase in the dielectric constant of the solution with increasing salt content.
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- Orädd, Greger, et al.
(författare)
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NMR studies of binary and ternary systems of phosphatidylcholines
- 2007
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Ingår i: European Biophysics Journal, 2007 July, Volume 36, Supplement 1. ; , s. 1-278
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Lipid lateral segregation in biomimicking model membranes has recently become a topic of great interest due to the biological coupling to the concept of functional rafts. In the studies of liquid-liquid phase coexistence it is found that lateral phase separation into liquid ordered and liquid disordered phases takes place in ternary systems consisting of one unsaturated and one saturated lipid, together with a sterol. The phase behavior is critically dependent on the components with respect to chain length, degree of unsaturation and sterol structure and the driving force of the phase separation is closely related to the ordering effect of the sterol on the lipid chains. This study presents NMR data for binary and ternary systems composed of mixtures of sphingomyelins, phosphatidylcholines and cholesterol. Order parameters were obtained from perdeuterated chains in the saturated lipid and diffusion data of both the saturated and unsaturated lipids were measured with the pulsed field gradient NMR method. Data were analyzed with regard to phase separation into liquid and solid phases.
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- Orädd, Greger
(författare)
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NMR Studies of Oriented Domain-Forming Model Membranes
- 2007
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Ingår i: Bioactive Lipids in the Lipidomics Era (C2).
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Summary of MeetingThe identification of many receptors and targets of bioactive lipid mediators has led to research uncovering their roles in regulating many important normal and pathophysiological processes. It has become evident that the biological activities and functions of lipid signaling molecules are dependent on both their molecular structures and complex cell-specific interactions among the different pathways involved in their biosynthesis and metabolism. The growing complexity of these interactions and the thousands of cellular lipids, together with genomics and proteomics technology already in place, has emphasized the need for development of complementary lipidomics technology. The goal of this meeting is to bring investigators studying signaling and metabolism of bioactive lipids together with researchers who are now developing lipidomics methods for exhaustive characterization and systematic measurement by mass spectrometry of the lipidome, ie cellular lipids, their precursors and their metabolites. The program of this meeting has been designed to foster and synergize research in these areas.
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