Measuring polymer surface ordering differences in air and water by sum frequency generation vibrational spectroscopy

Jie Wang, Z. Pászti, Mark A. Even, Zhan Chen

Research output: Contribution to journalArticle

161 Citations (Scopus)

Abstract

Molecular structures of poly(n-butyl methacrylate) (PBMA) at the PBMA/air and PBMA/water interfaces have been studied by sum frequency generation (SFG) vibrational spectroscopy, PBMA surfaces in both air and water are dominated by the methyl groups of the ester side chains. The average orientation and orientation distribution of these methyl groups at the PBMA/air and PBMA/water interfaces are different, indicating that surface restructuring occurs when the PBMA sample contacts water. Analysis shows that the orientation distribution of side chain methyl groups on the PBMA surface is narrower in water than that in air, indicating that the PBMA surface can be more ordered in water. To our knowledge, this is the first time that quantitative comparisons between molecular surface structures of polymers in air and in water have been made. Two assumptions on the orientation distribution function, including a Gaussian distribution and a formula based on the maximum entropy approach, are used in the analysis. It has been found that the orientation angle distribution function deduced by the Gaussian distribution and the maximum entropy distribution are quite similar, showing that the Gaussian distribution is a good approximation for the angle distribution. The effect of experimental error on the deduced orientational distribution is also discussed.

Original languageEnglish
Pages (from-to)7016-7023
Number of pages8
JournalJournal of the American Chemical Society
Volume124
Issue number24
DOIs
Publication statusPublished - Jun 19 2002

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Vibrational spectroscopy
Spectrum Analysis
Polymers
Air
Water
Gaussian distribution
Normal Distribution
Distribution functions
Entropy
Molecular Structure
poly(butyl methacrylate)
Surface structure
Molecular structure
Esters

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Measuring polymer surface ordering differences in air and water by sum frequency generation vibrational spectroscopy. / Wang, Jie; Pászti, Z.; Even, Mark A.; Chen, Zhan.

In: Journal of the American Chemical Society, Vol. 124, No. 24, 19.06.2002, p. 7016-7023.

Research output: Contribution to journalArticle

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AB - Molecular structures of poly(n-butyl methacrylate) (PBMA) at the PBMA/air and PBMA/water interfaces have been studied by sum frequency generation (SFG) vibrational spectroscopy, PBMA surfaces in both air and water are dominated by the methyl groups of the ester side chains. The average orientation and orientation distribution of these methyl groups at the PBMA/air and PBMA/water interfaces are different, indicating that surface restructuring occurs when the PBMA sample contacts water. Analysis shows that the orientation distribution of side chain methyl groups on the PBMA surface is narrower in water than that in air, indicating that the PBMA surface can be more ordered in water. To our knowledge, this is the first time that quantitative comparisons between molecular surface structures of polymers in air and in water have been made. Two assumptions on the orientation distribution function, including a Gaussian distribution and a formula based on the maximum entropy approach, are used in the analysis. It has been found that the orientation angle distribution function deduced by the Gaussian distribution and the maximum entropy distribution are quite similar, showing that the Gaussian distribution is a good approximation for the angle distribution. The effect of experimental error on the deduced orientational distribution is also discussed.

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