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Unwinding of poly(ethylene oxide) chains grafted on silica under a shear flow of cyclohexane, observed by spin-labelling (1999)

Chikhi, M. ; Afif, A. ; Hommel, H. ; [et al.]

Springer

Colloid & polymer science 277 (1999), S. 965-971

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ISSN: 1435-1536

Keywords: Key words Solid/fluid interface processes ; Amorphous and polymeric materials ; Magnetic resonance and relaxation

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Poly(ethylene oxide) chains of molecular weight 2000 have been grafted on pyrogenic silica, spin-labelled at their free end and put into contact with cyclohexane. The electron paramagnetic resonance of the nitroxide free radical gives evidence of two specific environments: namely, trains adsorbed on the solid with a restricted motion and loops and tails protruding into solution with a high mobility. The dynamic parameters such as the rotational correlation time and the static ones such as the fraction of each population have been evaluated. Under a flow of solvent the unwinding of the chains has been observed with increasing flow rate in our experimental range. Some mechanisms are proposed to explain this behaviour.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s003960050476

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Thickness of a silica-tethered poly(ethylene oxide) layer measured by spin labeling (1995)

Hommel, H. ; Touhami, A. ; Halli, A. ; [et al.]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 2189-2198

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ISSN: 0887-6266

Keywords: poly(ethylene oxide) ; EPR spectroscopy ; spin labeling ; silica grafting ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: EPR spectroscopy of labeled poly(ethylene oxide) (PEO) grafted on silica has been used to characterize the conformation and local dynamics of the chains. Grafted molecules of MW 2000 with grafting ratios of 0.045, 0.057, 0.126, and 0.42 molecules/nm2 were in contact with benzene. The mobility of the label was compared with that observed for solution of PEO from very diluted to highly concentrated and even bulk PEO. Thus, the concentration inside the grafted layer could be evaluated and also the thickness, which evolves rather linearly with the grafting ratio. © 1995 John Wiley & Sons, Inc.

Additional Material: 12 Ill.