Mass density of polystyrene thin films measured by twin neutron reflectivity

Wallace, W.E.; Tan, Nora C. Beck; Wu, Wen‐Li; Satija, Sushil K.

doi:10.1063/1.475769

Cited by 81 publications

(61 citation statements)

References 28 publications

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“…Such a large change in the average density of a thin film polymer has not been observed in experiment. 53,67 Thus, a reduced average film density cannot be used to explain the present observations. A mechanism focusing on changes at the interface between the polymer and the brush is more likely to be operative.…”

Section: Effect Of the Polymer-substrate Interfacecontrasting

confidence: 44%

Anomalous Dynamics of Polymer Films

Tsui

2008

Series in Soft Condensed Matter

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This chapter reviews the recent experiments involving the dynamics of polymer films with thickness comparable to the gyration radius of the polymer, which overwhelmingly show that their glass transition temperature, T g , depends on the film thickness and can sometimes differ significant from that of the bulk. The greatest mystery is the onset film thickness of this phenomenon being ~50 nm, much larger than the typical cooperativity size (~3 nm) of glass transition. While the sliding chain model [De Gennes, Eur. Phys. J. E (2000)] can qualitatively explain the results of the high molecular weight (M w ) freely-standing films, it fails to account for those of the low-M w freely-standing films and the supported films. For the latter two, at least two theories, i.e., the percolation theory [Long et al., ibid (2001)] and surface capillary wave theory [Herminghaus et al., ibid (2001)] have been proposed that can account for the observed thickness dependence of thin film T g . However, experimental data available at this time do not allow the theories to be distinguished. We briefly outline the physical ideas of these theories, and delineate how dynamical measurements of nanometer thick films may provide important insights about the problem.

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Section: Effect Of the Polymer-substrate Interfacecontrasting

confidence: 44%

Anomalous Dynamics of Polymer Films

Tsui

2008

Series in Soft Condensed Matter

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“…It is still a matter of debate whether or not the density of a polymer in an ultra-thin film is different from its density in bulk. polymer density in annealed films thicker than 10 nm is the same as in bulk [33,34], and the density at the interface with air and with a supporting substrate differs from the bulk density over distances of at most a few nanometers [35][36][37][38].…”

Section: Thickness Dependencementioning

confidence: 73%

Solvent retention in thin polymer films studied by gas chromatography

Garcia-Turiel

Jérôme

2007

Colloid Polym Sci

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Thin polystyrene films were produced by spin coating from solutions in toluene. The amount of solvent retained in the films after drying for different times was measured using gas chromatography. Whereas for thicker films (thickness > 200 nm), the relative amount of solvent in the films is less than a few percent, the proportion of toluene increases significantly in thinner films. The thickness dependence of the mass of retained solvent shows that the solvent is mainly retained at the polymer-substrate interface. The solvent desorption rate exhibits no variation on the film thickness.

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“…18 ͑The possible change in atom density ͑not mass density͒ due to deuteration has not been explicitly considered͒. Earlier work on the same polystyrene, prepared in the same fashion, using twin neutron reflectivity 19 found the value for thinner films ͑6.5-75.0 nm͒ to be equal to the bulk value but only to within a few percent due to measurement uncertainty primarily found in the data fitting. Thus, neutron interferometry is envisioned as a way to create more accurate thin film density standards which can be used in the calibration of many types of instruments.…”

Section: ⌰ϭ4dnbt ͑3͒mentioning

confidence: 95%

Application of neutron interferometry to the measurement of thin film density

Wallace

Jacobson

Arif

et al. 1999

Applied Physics Letters

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The application of neutron interferometry to the measurement of the atom density of polymer thin films (<1 μm thick) supported on silicon substrates is described. Polymer films were chosen primarily for their fixed, well-defined stoichiometry; however, the technique is applicable to films of any elemental composition. The wavelength-independent phase shift of a beam of thermal neutrons passing through the sample gives a measure of the product of the film atom density, the film thickness, the lattice spacing of the silicon interferometer, and the scattering lengths of the constituent elements of the film. The film thickness was found by x-ray reflectivity while the other two parameters are well-defined quantities. The technique does not rely on complex mathematical modeling of physical processes nor on thin film standards for data interpretation. With some refinements, neutron interferometry is envisioned as an important tool in the creation of thin films having well-defined densities which will be useful in the calibration of many analysis techniques.

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Mass density of polystyrene thin films measured by twin neutron reflectivity

Cited by 81 publications

References 28 publications

Anomalous Dynamics of Polymer Films

Anomalous Dynamics of Polymer Films

Solvent retention in thin polymer films studied by gas chromatography

Application of neutron interferometry to the measurement of thin film density

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