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Volumn 108, Issue 16, 1998, Pages 6996-7009

Simple liquids confined to molecularly thin layers. I. Confinement-induced liquid-to-solid phase transitions

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Indexed keywords


EID: 0343754431     PISSN: 00219606     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.476114     Document Type: Article
Times cited : (471)

References (74)
  • 1
    • 0005954740 scopus 로고
    • Doubleday, New York
    • D. Tabor, Friction (Doubleday, New York, 1973).
    • (1973) Friction
    • Tabor, D.1
  • 19
  • 32
    • 0031374241 scopus 로고    scopus 로고
    • A. Tkatchenko and Y. Rabin, Solid State Commun. 103, 361 (1997); Langmuir 13, 7146 (1997).
    • (1997) Langmuir , vol.13 , pp. 7146
  • 36
  • 46
    • 85034297719 scopus 로고    scopus 로고
    • note
    • 1 when carrying the top lens mounting assembly.
  • 51
    • 85034276862 scopus 로고    scopus 로고
    • note
    • The data exclude the early pioneering report by Horn and Israelachvili (Ref. 18), where the presence of trace amounts of water was later implicated (Ref. 17) as being responsible for the weakness of the oscillations.
  • 52
    • 85034275985 scopus 로고    scopus 로고
    • note
    • Such impurities can come from the reactants diethoxydimethylsilane or (more probably) hexamethyldisiloxane. An additional possible side product is octamethyltrisiloxane. These have a linear structure, and if not removed they may suppress layering and mask the sharp liquid-to-solid transitions.
  • 54
    • 85034282678 scopus 로고    scopus 로고
    • private communication
    • Indeed, in a number of the early experiments where our distillation procedure was not adequate, with OMCTS in particular, oscillating surface forces were absent or much reduced. Similar suppression of the oscillating forces was observed also after several days of an experiment, by which time impurities, i.e., foreign molecules, had crept in [similar effects were seen by A. Berman and J. N. Israelachvili (private communication)]. In these cases we also did not observe the sharp liquid-to-solid transition on increasing confinement described in this paper. As noted, such experiments were aborted.
    • Berman, A.1    Israelachvili, J.N.2
  • 56
    • 85034299753 scopus 로고    scopus 로고
    • note
    • eff evaluated may have an uncertainty of about a factor of 10 in either direction.
  • 59
    • 85034284331 scopus 로고    scopus 로고
    • note
    • In the study of OMCTS published in Ref. 21, which indicated a gradual increase in the fluid viscosity on progressive confinement, and, in contrast to several other studies (Refs. 7, 15, 16, and 69), an absence of any zero-shear-rate yield stress upon shear, the liquid used was similar to that used in the present investigation (containing up to 1% impurities), save that it was not distilled prior to its introduction to the cell (Ref. 72). This contrasts with the procedure described in Sec. II B. The structural oscillations reported for OMCTS in that study (Ref. 21) were also much reduced in magnitude (see open circles in Fig. 5), strongly suggesting the presence of foreign molecules (Ref. 50). These may have interfered with molecular ordering (such as layering) in the confined OMCTS films, as noted also in Sec. III A (Ref. 52), thereby preventing the sharp liquid-solid transition from occuring in the sample studied in Ref. 21. This interesting report (Ref. 21) is thus of particular significance in that it may suggest that the presence of trace amounts of foreign molecules has large effects on the properties of thin OMCTS films.
  • 69
    • 85034276058 scopus 로고    scopus 로고
    • note
    • -2/3 relation suggested earlier (Ref. 20) for some liquids, including OMCTS (n = 3) at comparable shear rates (see Ref. 57 for possible origins of this difference).
  • 73
    • 85034290198 scopus 로고    scopus 로고
    • note
    • We are indebted to Dr. Robin Ball for suggesting this approach.
  • 74
    • 85034281668 scopus 로고    scopus 로고
    • private communication
    • S. Granick (private communication) has informed us that similar results to Ref. 21 were obtained also when their OMCTS samples were distilled. However, in contrast to several other studies (Refs. 7, 15, 16, and 69), a zero-shear-rate yield stress (indicating solidlike behavior) was still not observed when thin films (n≤3) of their OMCTS samples were sheared. We do not have an explanation for this discrepancy, other than our suggestion above (Ref. 57).
    • Granick, S.1


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