Schlossman, M. L.Schwartz, D. K.Kawamoto, E. H.Kellogg, G. J.Pershan, PeterKim, M. W.Chung, T. C.2013-03-011991Schlossman, M. L., D. K. Schwartz, E. H. Kawamoto, G. J. Kellogg, Peter S. Pershan, M. W. Kim, and T. C. Chung. 1991. X-ray reflectivity of a polymer monolayer at the water/vapor interface. Journal of Physical Chemistry 95(17): 6628-6632.0022-3654http://nrs.harvard.edu/urn-3:HUL.InstRepos:10357569X-ray specular reflectivity from a monolayer of partially hydroxylated 1,2-polybutadiene (50% butyl alcohol random substitution) at the water/vapor interface was measured from below the critical wavevector for water, 0.0217 Å\(^{-1}\), to \(Q_z\) \(\cong\) 0.6 Å\(^{-1}\) (where \(Q_z\) is the transferred momentum normal to the interface). The sample was prepared on a Langmuir trough, and measurements were made at five different surface densities in the high-pressure, or saturated, region of the isotherm. The measured reflectivity is interpreted to obtain a profile of the average electron density p(z) as a function of distance z along the surface normal. The profile has a local maximum that is approximately 10% larger than the electron density in bulk crystalline 1,2-polybutadiene. At the highest pressures the width of the liquid/vapor interface is \(\sim\) 10% larger than the value calculated from thermal capillary waves using in situ measurements of the surface tension; however, for smaller pressures the measured and calculated values agree.en-USJournal Article10.1021/j100170a046