Precise measurement of the self-diffusion coefficient for poly(ethylene glycol) in aqueous solution using uniform oligomers

2005 ◽  
Vol 122 (24) ◽  
pp. 244914 ◽  
Author(s):  
Kayori Shimada ◽  
Haruhisa Kato ◽  
Takeshi Saito ◽  
Shigetomo Matsuyama ◽  
Shinichi Kinugasa
Keyword(s):  
Aqueous Solution ◽  
Diffusion Coefficient ◽  
Ethylene Glycol ◽  
Precise Measurement ◽  
The Self ◽  
Poly Ethylene Glycol ◽  
Self Diffusion ◽  
Poly Ethylene ◽  
Self Diffusion Coefficient

scholarly journals Concentration dependence of lipopolymer self-diffusion in supported bilayer membranes

2010 ◽  
Vol 8 (54) ◽  
pp. 127-143 ◽  
Author(s):  
Huai-Ying Zhang ◽  
Reghan J. Hill
Keyword(s):  
Diffusion Coefficient ◽  
Ethylene Glycol ◽  
Reaction Diffusion ◽  
Poly Ethylene Glycol ◽  
Frictional Drag ◽  
Mole Percent ◽  
Self Diffusion ◽  
Reaction Diffusion Model ◽  
Poly Ethylene ◽  
Self Diffusion Coefficient

Self-diffusion coefficients of poly(ethylene glycol)2k-derivatized lipids (DSPE-PEG2k-CF) in glass-supported DOPC phospholipid bilayers are ascertained from quantitative fluorescence recovery after photobleaching (FRAP). We developed a first-order reaction–diffusion model to ascertain the bleaching constant, mobile fraction and lipopolymer self-diffusion coefficient D s at concentrations in the range c ≈ 0.5–5 mol%. In contrast to control experiments with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (ammonium salt) (DOPE-NBD) in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), the lipopolymer self-diffusion coefficient decreases monotonically with increasing concentration, without a distinguishing mushroom-to-brush transition. Our data yield a correlation D s = D 0 /(1 + α c ), where D 0 ≈ 3.36 µm 2 s −1 and α ≈ 0.56 (with c expressed as a mole percent). Interpreting the dilute limit with the Scalettar–Abney–Owicki statistical mechanical theory for transmembrane proteins yields an effective disc radius a e ≈ 2.41 nm. On the other hand, the Bussell–Koch–Hammer theory, which includes hydrodynamic interactions, yields a e ≈ 2.92 nm. As expected, both measures are smaller than the Flory radius of the 2 kDa poly(ethylene glycol) (PEG) chains, R F ≈ 3.83 nm, and significantly larger than the nominal radius of the phospholipid heads, a l ≈ 0.46 nm. The diffusion coefficient at infinite dilution D 0 was interpreted using the Evans–Sackmann theory, furnishing an inter-leaflet frictional drag coefficient b s ≈ 1.33 × 10 8 N s m −3 . Our results suggest that lipopolymer interactions are dominated by the excluded volume of the PEG-chain segments, with frictional drag dominated by the two-dimensional bilayer hydrodynamics.

Investigation on the Diffusion Behavior of Mo-Ni Interface

2010 ◽  
Vol 152-153 ◽  
pp. 1607-1610 ◽  
Author(s):  
Wei Chan Cao ◽  
Shu Hua Liang ◽  
Yue Xin Xue ◽  
Xian Hui Wang
Keyword(s):  
Solid Solution ◽  
Diffusion Coefficient ◽  
Electron Microscope ◽  
Intermetallic Compound ◽  
Diffusion Layer ◽  
Interdiffusion Coefficient ◽  
The Self ◽  
Diffusion Behavior ◽  
Self Diffusion ◽  
Self Diffusion Coefficient

In order to gain a deep insight into the mechanism of Ni-doped Mo activated sintering process, the diffusion behavior of Mo-Ni interface was studied utilizing a Mo-Ni diffusion couple. The phase structure and composition on the diffusion layer were characterized and analyzed by means of scanning electron microscope and transmission electron microscope, the self diffusion coefficient and interdiffusion coefficient were calculated. The results show that a diffusion layer is formed between Mo and Ni after sintering at 1223k for 1h, which is comprised of a δ-NiMo intermetallic compound and a limit solid solution containing small amounts of nickel. The self diffusion coefficient and interdiffusion coefficient are 2.068×10-18cm2/s and 4.5×10-12cm2/s, respectively. It is suggested that the diffusion rate of Mo in δ-NiMo intermetallic compound and a limit solid solution containing small amounts of nickel is 106 times bigger than that of self diffusion, and the intermetallic compound layer provides a short diffusion path for Mo activated sintering.

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