Partial structure factor analysis of neutron reflectometry from spread monolayers of isotactic polymethyl methacrylate

Abstract

AbstractNeutron reflectivity data for isotactic polymethyl methacrylate monolayers spread at the air‐water interface have been analysed using the kinematic approximation. For surface concentrations up to 1.0 mg m−2 the data are well modelled by a uniform layer of thickness circa 20Å. Water may be uniformly dispersed throughout the film. However, to obtain agreement with the experimental reflectivities, a proportion of air must be included in the film which agrees with the findings of an earlier optical matrix type analysis. For surface concentration above 1 mg m−2, the uniform layer model does not reproduce the surface concentrations and the data is better fitted by a layer with a Gaussian distribution of segments in the aqueous phase. The benefits of the kinematic approximation are that an insight into the organisation of polymers at the air‐water interface can be obtained rapidly without the need for detailed fitting procedures inherent in the use of optical matrix methods.