Absolute Molecular Orientational Distribution of the Polystyrene Surface

Published

April 1, 2001

Author(s)

Kimberly A. Briggman, John C. Stephenson, William E. Wallace, Lee J. Richter

Abstract

Vibrationally-resonant sum frequency generation (VR-SFG) has been used to study the absolute molecular orientational distribution of the pendant phenyl groups at the free surface of polystyrene (PS) thin films on oxidized Si substrates. Characterization of the dependence of the VR-SFG on film thickness allows unique identification of the origin of the signal, e.g., free surface, bulk, buried interface. For films 2 . VR-SFG of a self-assembled phenylsiloxane layer is used to calibrate the relative phase between the vibrationally resonant phenyl ring hyperpolarizability and the Si/O₂ interface non-resonant hyperpolarizability. It is found that the phenyl groups at the PS/air interface are oriented away from the polymer film. Quantitative analyses of the orientation distribution for both the PS free interface and the phenylsiloxane monolayer are reported. The phenyl groups at the PS free surface are tilted away from the surface normal in an angular range near 57 degrees.

Citation

Journal of Physical Chemistry B

Volume

105

Issue

No. 14

Pub Type

Journals

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Keywords

molecular structure, nonlinear optics, polymer, polystyrene, sum-frequency generation, surface

Citation

Briggman, K. , Stephenson, J. , Wallace, W. and Richter, L. (2001), Absolute Molecular Orientational Distribution of the Polystyrene Surface, Journal of Physical Chemistry B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=841486 (Accessed October 13, 2025)