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Thermal Expansion and Glass Transition Behaviour of Thin Polymer Films with and without a Free Surface Via Neutron Reflectometry

Published online by Cambridge University Press:  10 February 2011

D. J. Pochan ,
E. K. Lin ,
S. Satija ,
S. Z. D. Cheng  and
Wen-Li Wu
D. J. Pochan
Affiliation:
Electronic Applications Group, Polymer Division, NIST, Gaithersburg, MD
E. K. Lin
Affiliation:
Electronic Applications Group, Polymer Division, NIST, Gaithersburg, MD
S. Satija
Affiliation:
NIST Center for Neutron Research, NIST, Gaithersburg, MD
S. Z. D. Cheng
Affiliation:
Department of Polymer Science, University of Akron, Akron, OH
Wen-Li Wu
Affiliation:
Electronic Applications Group, Polymer Division, NIST, Gaithersburg, MD
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Abstract

The thermal expansion of thin deuterated polystyrene (dPS) films supported on energetically repulsive, fluorinated polyimide (PI) substrates (PI/dPS bilayer) was measured via neutron reflectometry as a function of initial dPS film thickness. Film thickness was measured before and after capping with a top layer of the same repulsive, high glass transition polyimide that comprised the substrate layer (PI/dPS/PI trilayer) in an attempt to observe any effects of the dPS free surface in the bilayer geometry. Bulk thermal expansion behavior, characterized by a discontinuous change in coefficient of thermal expansion (CTE) at the glass transition (Tg), is observed in films with thickness > 70 rim. For thicknesses between 70 nm and 40 nm a transition is seen from bulk behavior in bilayer films to glassy thermal behavior in the trilayer films persisting up to 20 °C above the bulk Tg. In films with thickness < 40 nm the bulk glassy CTE persists well above the bulk Tg for both bilayer and trilayer films

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 543: Symposium W – Dynamics in Small Confining Systems IV , 1998 , 163
Copyright
Copyright © Materials Research Society 1999

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References

1. Baschnagel, J. and Binder, K., Macromolecules. 28, 6808 (1995).Google Scholar
2. Pakula, T., J. Chem. Phys. 95, 4658 (1991).Google Scholar
3. Wallace, W.E., van Zanten, J.H., Wu, W.L., Phys. Rev. E. 52, R3329 (1995).Google Scholar
4. van Zanten, J.H., Wallace, W.E., Wu, W.L.., Phys. Rev. E. 53, R2053 (1996).Google Scholar
5. Keddie, J.L., Jones, R.A.L., Cory, R.A., Europhys. Lett. 27, 59 (1994).Google Scholar
6. Forrest, J.A., Dalnoki-Veress, K., Dutcher, J.R., Phys. Rev. E. 56, 5707 (1997).Google Scholar
7. Kajiyama, T., Tanaka, K., Takahara, A., Macromolecules. 30, 280 (1997).Google Scholar
8. Prucker, O., Christian, S., Bock, H., Frank, C.W., Knoll, W., Macromol. Chem. Phys. 199, 1435 (1998).Google Scholar
9. Hall, D.B., Miller, R.D., Torkelson, J.M., J. P. Sci., B: Phys. 35, 2795. (1997).Google Scholar
10. Kwan, S.C.M., Wu, C., Li, F., Savitski, E.P., Harris, F.W., Cheng, S.Z.D., Macromol. Chem. Phys. 198, 3605 (1997).Google Scholar
11. According to ISO 31–8 the term “molecular weight” has been replaced by “relative molecular mass,” symbol Mr Thus, if this nomenclature were to be followed in thispublication, one would write Mr, n instead of the historically conventional M, for the number average molecular weight, with similar changes for Mw, Mz, and My, and it would be called the “number average relative molecular mass.” The conventional notation, rather than the ISO notation, has been employed for this publication.Google Scholar
12. The data in Figure 1 are presented along with the standard uncertainty (±) involved in the measurement.Google Scholar
13. The error in the fitted dPS film thickness at different respective temperatures is estimated to be Δthick = 0.1 Å by the fitting procedure which is based on a Marquart-Levenburg fit that minimizes a merit function, χ2, through variation of a group of specified parameters.(14–16) The small magnitude of the uncertainty estimate is a partial consequence of this fitting procedure which minimizes χ2 based on a set of optimized parameters (polyimide films and dPS film thickness, neutron scattering length density, and interfacial roughness between layers) whose individual errors are small but correlated.(16) Although an absolute measure of the individual uncertainty in the dPS film thickness would be beneficial it is not possible to obtain such an estimate for any fitted parameter value resulting from this type of χ2 fitting of the experimental data without imposing an arbitrary criteria of deviation between an optimum fit and a significantly less-than optimum fit. The error estimate provided by the χ2 routine is the least ambiguous estimate for the film thickness measurements in this study.Google Scholar
14. Ankner, J.F. and Majkrzak, C.F., SPIE. 1738, 260 (1992).Google Scholar
15. Press, W.H. et al., Numerical Recipes, 3 rd ed. Cambridge University Press, Cambridge, UK (1992).Google Scholar
16. Asmussen, A. and Riegler, H., J. Chem. Phys. 104, 8159 (1996).Google Scholar