NEXAFS depth profiling of surface segregation in block copolymer thin films

Macromolecules

Volumn 43, Issue 10, 2010, Pages 4733-4743

  Krishnan, Sitaraman ^a   Paik, Marvin Y ^b   Ober, Christopher K ^b   Martinelli, Elisa ^c   Galli, Giancarlo ^c   Sohn, Karen E ^d   Kramer, Edward J ^e   Fischer, Daniel A ^f  

^a Wallace H Coulter School of Engineering   (United States)

^b School of Chemical and Molecular Engineering   (United States)

^c UNIVERSITY OF PISA   (Italy)

^d Santa Barbara   (United States)

^e UNIVERSITY OF CALIFORNIA   (United States)

^f NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

BLOCK COPOLYMER FILMS; BLOCK COPOLYMER THIN FILMS; CARBON ATOMS; COMB-LIKE; COMPOSITIONAL DEPTH PROFILING; CONCENTRATION PROFILES; CONCENTRATION-DEPTH PROFILE; DEPTH RESOLUTION; DIBLOCK COPOLYMER; FLUOROALKYL GROUP; HIGH SURFACE ENERGY; HOMOPOLYMERS; LAMELLAR LAYERS; MICRO-DOMAINS; MICROPHASE SEPARATED; MICROPHASES; NEAR SURFACE REGIONS; NEXAFS SPECTROSCOPY; PHENYL GROUP; PHENYL RINGS; POLYSTYRENE BLOCK; RANDOM COPOLYMER; SIDE CHAINS; SPONTANEOUS FORMATION; STYRENIC MONOMERS; SURFACE COMPOSITIONS; SURFACE CONCENTRATION; SURFACE DEPLETION; SURFACE ENERGIES; SURFACE REGION; WATER INTERFACE; WATER SURFACE;

ATOMS; BLOCK COPOLYMERS; CARBON FILMS; COPOLYMERIZATION; DEPTH PROFILING; ETHYLENE; ETHYLENE GLYCOL; INTERFACIAL ENERGY; PLASTIC PRODUCTS; POLYETHYLENE GLYCOLS; POLYETHYLENE OXIDES; POLYMER BLENDS; POLYMER FILMS; POLYMERS; POLYSTYRENES; SURFACE CHEMISTRY; SURFACE SEGREGATION; SURFACE TENSION; THIN FILMS; X RAY ABSORPTION NEAR EDGE STRUCTURE SPECTROSCOPY;

SURFACE RECONSTRUCTION;

EID: 77952479565     PISSN: 00249297     EISSN: None     Source Type: Journal    
DOI: 10.1021/ma902866x     Document Type: Article

References (62)

1. Martinelli, E.; Agostini, S.; Galli, G.; Chiellini, E.; Glisenti, A.; Pettitt, M. E.; Callow, M. E.; Callow, J. A.; Graf, K.; Bartels, F. W. Langmuir 2008, 24, 13138-13147
2. Grozea, C. M.; Gunari, N.; Finlay, J. A.; Grozea, D.; Callow, M. E.; Callow, J. A.; Lu, Z.-H.; Walker, G. C. Biomacromolecules 2009, 10, 1004-1012
3. Gudipati, C. S.; Greenlief, C. M.; Johnson, J. A.; Prayongpan, P.; Wooley, K. L. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 6193-6208
4. Gudipati, C. S.; Finlay, J. A.; Callow, J. A.; Callow, M. E.; Wooley, K. L. Langmuir 2005, 21, 3044-3053
5. Finlay, J. A.; Krishnan, S.; Callow, M. E.; Callow, J. A.; Dong, R.; Asgill, N.; Wong, K.; Kramer, E. J.; Ober, C. K. Langmuir 2008, 24, 503-510
6. Krishnan, S.; Wang, N.; Ober, C. K.; Finlay, J. A.; Callow, M. E.; Callow, J. A.; Hexemer, A.; Sohn, K. E.; Kramer, E. J.; Fischer, D. A. Biomacromolecules 2006, 7, 1449-1462
7. Krishnan, S.; Ayothi, R.; Hexemer, A.; Finlay, J. A.; Sohn, K. E.; Perry, R.; Ober, C. K.; Kramer, E. J.; Callow, M. E.; Callow, J. A.; Fischer, D. A. Langmuir 2006, 22, 5075-5086
8. Weinman, C. J.; Finlay, J. A.; Park, D.; Paik, M. Y.; Krishnan, S.; Sundaram, H. S.; Dimitriou, M.; Sohn, K. E.; Callow, M. E.; Callow, J. A.; Willis, C. L.; Kramer, E. J.; Ober, C. K. Langmuir 2009, 25, 12266-12274
9. Vaidya, A.; Chaudhury, M. K. J. Colloid Interface Sci. 2002, 249, 235-245
10. Makal, U.; Uslu, N.; Wynne, K. J. Langmuir 2007, 23, 209-216
11. Jannasch, P. Macromolecules 1998, 31, 1341-1347
12. Russell, T. P. Science 2002, 297, 964-967
13. Luzinov, I.; Minko, S.; Tsukruk, V. V. Prog. Polym. Sci. 2004, 29, 635-698
14. Koberstein, J. T. J. Polym. Sci., Part B: Polym. Phys. 2004, 42, 2942-2956
15. Martinelli, E.; Menghetti, S.; Galli, G.; Glisenti, A.; Krishnan, S.; Paik, M. Y.; Ober, C. K.; Smilgies, D.-M.; Fischer, D. A. J. Polym. Sci., Part A: Polym. Chem. 2008, 47, 267-284
16. Theato, P.; Brehmer, M.; Conrad, L.; Frank, C. W.; Funk, L.; Yoon, D. Y.; Lüning, J. Macromolecules 2006, 39, 2592-2595
17. Weinman, C. J.; Krishnan, S.; Park, D.; Paik, M. Y.; Wong, K.; Fischer, D. A.; Handlin, D. L., Jr.; Kowalke, G. L.; Wendt, D. E.; Sohn, K. E.; Kramer, E. J.; Ober, C. K. Polym. Mater Sci. Eng. Prepr. 2007, 96, 597-598
18. Liu, X.; Mao, Y.; Mathias, E. V.; Ma, C.; Franco, O.; Ba, Y.; Kornfield, J. A.; Wang, T.; Xue, L.; Zhou, B.-S.; Yen, Y. J. Sol-Gel Sci. Technol. 2008, 45, 269-278
19. Howarter, J. A.; Youngblood, J. P. J. Colloid Interface Sci. 2009, 329, 127-132
20. Krishnan, S.; Kwark, Y.-J.; Ober, C. K. Chem. Rec. 2004, 4, 315-330
21. Krausch, G. Mater. Sci. Eng., R. 1995, R14, 1-94
22. Bucknall, D. G. Prog. Mater. Sci. 2004, 49, 713-786
23. Kramer, E. J. Physica B 1991, 173, 189-198
24. Kerle, T.; Scheffold, F.; Losch, A.; Steiner, U.; Schatz, G.; Klein, J. Acta Polym. 1997, 48, 548-552
25. Wang, C.; Araki, T.; Watts, B.; Harton, S.; Koga, T.; Basu, S.; Ade, H. J. Vac. Sci. Technol. A 2007, 25, 575-586
26. Gagnon, D. R.; McCarthy, T. J. J. Appl. Polym. Sci. 1984, 29, 4335-4340
27. Cross, E. M.; McCarthy, T. J. Macromolecules 1990, 23, 3916-3922
28. Tyler, B. J.; Castner, D. G.; Ratner, B. D. Surf. Interface Anal. 1989, 14, 443-450
29. Senshu, K.; Yamashita, S.; Mori, H.; Ito, M.; Hirao, A.; Nakahama, S. Langmuir 1999, 15, 1754-1762
30. Beamson, G.; Alexander, M. R. Surf. Interface Anal. 2004, 36, 323-333
31. Dwyer, V. M. Surf. Interface Anal. 1994, 21, 637-642
32. For example, see: Teruaki, H.; Wang, J.; Xiang, M.; Li, X.; Mitsuru, U.; Ober, C. K.; Genzer, J.; Sivaniah, E.; Kramer, E. J.; Fischer, D. A. Macromolecules 2000, 33, 8012-8019
33. Zentel and coworkers have further investigated surface construction in a library of block copolymers with different functional side chains using contact angle measurements and AFM; cf.: Funk, L.; Brehmer, M.; Zentel, R.; Kang, H.; Char, K. Macromol. Chem. Phys. 2008, 209, 52-63
34. 3/mol where x and y are the average numbers of ethylene glycol and perfluoroethylene groups, respectively, in each monomer: Bicerano, J. Prediction of Polymer Properties, 2 nd ed.; Marcel Dekker: New York, 1996.
35. Specular reflection of the incident X-ray beam, by the sample onto the detector, occurs at an X-ray incidence angle of 72°. Although specular reflection is expected to affect only fluorescence yield measurements, we found that the electron yield was also affected. Hence, = 70° was not used in our analysis.
36. Stöhr, J. Analysis of K-shell excitation spectra by curve fitting. In NEXAFS Spectroscopy; Springer Series in Surface Science 25; Springer: New York, 1992; p 211.
37. Rosenberg, R. A.; Love, P. J.; Rehn, V. Phys. Rev. B: Condens. Matter Mater. Phys. 1986, 33, 4034-4037
38. Krishnan, S.; Ober, C. K.; Hexemer, A.; Kramer, E. J.; Fischer, D. A. Polym. Mat. Sci. Eng. Prepr. 2006, 94, 672-673
39. Lenhart, J. L.; Fischer, D. A.; Sambasivan, S.; Lin, E. K.; Jones, R. L.; Soles, C. L.; Wu, W.-L.; Goldfarb, D. L.; Angelopoulos, M. Langmuir 2005, 21, 4007-4015
40. Klein, R. J.; Fischer, D. A.; Lenhart, J. L. Langmuir 2008, 24, 8187-8197
41. Stöhr, J. The anglular dependence of resonance intensities. In NEXAFS Spectroscopy; Springer Series in Surface Science 25; Springer: New York, 1992; p 276.
42. For thin films of perfluorinated polyether on graphite, Sohn et al. demonstrated that the depth variation of carbon atom density must be considered for accurate compositional depth profiling using NEXAFS (ref 43). However, the simplifying assumption of depth-invariant carbon atom density is believed to be satisfactory for comparison of surface compositions of the polymers used in the present study (cf. Supporting Information).
43. Sohn, K. E.; Dimitriou, M. D.; Genzer, J.; Fischer, D. A.; Hawker, C. J.; Kramer, E. J. Langmuir 2009, 25, 6341-6348
44. C - C peak near 285.2 eV has contributions from carbon atoms of the phenyl rings in the PEGylated/fluorinated monomer, and in the copolymer, also from the phenyl ring carbon atoms of the styrene monomer.
45. a vs - data, were found to be same as that of polystyrene phenyl ring carbon atoms.
46. Krishnan, S.; Ward, R. J.; Hexemer, A.; Sohn, K. E.; Lee, K. L.; Angert, E. R.; Fischer, D. A.; Kramer, E. J.; Ober, C. K. Langmuir 2006, 22, 11255-11266
47. Khanna, V.; Cochran, E. W.; Hexemer, A.; Stein, G. E.; Fredrickson, G. H.; Kramer, E. J.; Li, X.; Wang, J.; Hahn, S. F. Macromolecules 2006, 39, 9346-9356
48. Neto, C.; James, M.; Telford, A. M. Macromolecules 2009, 42, 4801-4808
49. Thomas, H. R.; O'Malley, J. J. Macromolecules 1979, 12, 323-329
50. Chen, D.; Gong, Y.; Huang, H.; He, T. Macromolecules 2007, 40, 6631-6637
51. Olayo-Valles, R.; Guo, S.; Lund, M. S.; Leighton, C.; Hillmyer, M. A. Macromolecules 2005, 38, 10101-10108
52. Senshu, K.; Yamashita, S.; Ito, M.; Hirao, A.; Nakahama, S. Langmuir 1995, 11, 2293-2300
53. Ishizone, T.; Han, S.; Hagiwara, M.; Yokoyama, H. Macromolecules 2006, 39, 962-970
54. Bosworth, J. K.; Paik, M. Y.; Ruiz, R.; Schwartz, E. L.; Huang, J. Q.; Ko, A. W.; Smilgies, D.-M.; Black, C. T.; Ober, C. K. ACS Nano 2008, 2, 1396-1402
55. The PS block is also comparable in size to the PEGylated/fluorinated block. The average number of carbon atoms along the backbone of the PS block is about 102. The root mean-square end-to-end distance, and the radius of gyration, of a PS homopolymer of this length is 4.6 and 1.9 nm, respectively.
56. Inelastic collision of an Auger electron results in a cascade of electrons produced by secondary electron emission processes. Most of these electrons have kinetic energies (KE) lower than the entrance grid bias of the detector (equal to ∼150 V), and are filtered off by the entrance grid. A small fraction of the inelastically scattered primary Auger electrons and the secondary electrons of the cascade, which have KE greater than 150 eV, can nevertheless get past the entrance grid and contribute to the partial electron yield. The fact that even some inelastically scattered electrons can contribute to the NEXAFS signal results in a higher probe-depth in NEXAFS depth-profiling than what can be achieved by detecting only unscattered electrons. The value electron escape depth has therefore been expected to be greater than IMFP, and a value of 1.95 nm has been reported for a perfluropolyether (Fomblin Z-03) thin film (cf. ref 43).
57. b for the 'dry' copolymer surfaces because of surface segregation of the fluorinated side chains.
58. b, which is expected to be equal to the stoichiometric number fraction of phenyl ring carbon atoms in the copolymer, is given by 6(n + m)/(8 n + 29 m).
59. 2 = 1). The surface compositions determined using NEXAFS spectroscopy indicate that this equation is not applicable to the copolymer surfaces of the present study, at least in the form stated above, because of surface reconstruction during the measurement of the contact angles.
60. Yuan, Y.; Shoichet, M. S. Macromolecules 2000, 33, 4926-4931
61. Whyman, G.; Bormashenko, E.; Stein, T. Chem. Phys. Lett. 2008, 450, 355-359
62. Julthongpiput, D.; Lin, Y.-H.; Teng, J.; Zubarev, E. R.; Tsukruk, V. V. Langmuir 2003, 19, 7832-7836