Spatial and Temporal Dependence of Diffusion in Polystyrene Thin Films on Silicon and Carbon Surfaces

Abstract

The strong inhibition of chain diffusion in thin polystyrene (PS) films has been observed near an attractive silicon surface, and diffusion remains inhibited out to distances of several radii of gyration from the surface. The present study seeks to determine the time dependence of the diffusion coefficient, and to examine the effect of a carbon surface on this diffusion. The sputter-deposited carbon surface may serve as a model for carbon-black particles employed in nanocomposites, which have recently been observed to reduce diffusion throughout a nanocomposite layer. The experiments employed a thin (∼15 nm) deuterated polystyrene (dPS) marker layer sandwiched between two normal PS layers. Deuterium profiles were monitored in the annealed samples by secondary ion mass spectrometry. Strong segregation was observed at the silicon surface, but was inhibited at the carbon surface, allowing the diffusion behaviour to be studied in the latter case over longer annealing times. A finite-element computer program was developed to fit the observed diffusion profiles. The variation of the diffusion coefficient with depth is shown to be consistent with previous results, and diffusion is comparable at both the carbon and silicon surfaces. The diffusion coefficient decreases roughly in proportion to t ^−1/2, and is discussed in the context of reptation theory.

Get full access to this article

View all access options for this article.

References

[1] Zhang Y et al 1999 Bull. Am. Phys. Soc. 44 613-613

[2] Bruinsma R 1990 Macromolecules 23 276-276

[3] Thompson P A , Grest G S and Robbins M O 1992 Phys. Rev. Lett. 68 3448-3448

[4] Hu H-W and Granick S 1992 Science 258 1339-1339

[5] Keddie J L , Jones R A L and Cory R A 1994 Europhys. Lett. 27 59-59

[6] Wallace W E , van Zanten J H and Wu W L 1995 Phys. Rev. E 52 R3329-R3329

[7] Forrest J A , Dalnoki-Veres K , Stevens J R and Dutcher J R 1996 Phys. Rev. Lett. 77 2002-2002

[8] van Zanten J H , Wallace W E and Wu W L 1996 Phys. Rev. E 53 R2053-R2053

[9] Zhao W , Rafailovich M H , Sokolov J , Fetters L H , Plano R , Sanyal M K , Sinha S K and Sauer B B 1993 Phys. Rev. Lett. 70 1453-1453

10.

[10] Zheng X , Sauer B B , Van Alsten J G , Schwarz S A , Rafailovich M H , Sokolov J and Rubinstein M 1995 Phys. Rev. Lett. 74 407-407

11.

[11] Bychuk O V and O’Shaughnessy B 1995 Phys. Rev. Lett. 74 1795-1795

12.

[12] Khare R , De Pablo J J and Yethiraj A 1996 Macromolecules 29 7910-7910

13.

[13] Semenov A N 1998 Phys. Rev. Lett. 80 1908-1908

14.

[14] Frank B , Gast A P , Russell T P , Brown H R and Hawker C 1996 Macromolecules 29 6531-6531

15.

[15] Liu Y , Russell T P , Samant M G , Strohr J , Brown H R , Cossy-Favre A and Diaz J 1997 Macromolecules 30 7768-7768

16.

[16] Lin E K , Wu W-L and Satija S K 1997 Macromolecules 30 7224-7224

17.

[17] Zheng X , Rafailovich M H , Sokolov J , Strzhemechny Y , Schwarz S A , Sauer B B and Rubinstein M 1997 Phys. Rev. Lett. 79 241-241

18.

[18] Jones R L , Kumar S K , Ho D L , Briber R M and Russell T P 1999 Nature 400 146-146

19.

[19] Strzhemechny Y , Shapovalov V , Zhou K G , Schwarz S A , Sokolov J and Rafailovich M H 1999 Proc. Materials Research Society 98 Fall Meeting (Boston, 1999)

20.

[20] Schwarz S A et al 1992 Mol. Phys. 76 937-937

21.

[21] Jones R A , Kramer E J , Rafailovich M H , Sokolov J and Schwarz S A 1989 Phys. Rev. Lett. 62 280-280

22.

[22] Schmidt I and Binder K 1985 J. Physique 46 1631-1631

23.

[23] Green P F and Kramer E J 1986 J. Mater. Res. 1 202-202

24.

[24] Kremer K and Guest G S 1995 Monte Carloand Molecular Dynamics Simulationsin Polymer Science ed K Binder (New York: Oxford University Press) ch 4