Neutron Scattering Study of the Structural Change Induced by Photopolymerization of AOT/D(2)O/Dodecyl Acrylate Inverse Microemulsions

Jolanta Marszalek, University of Southern Mississippi
John A. Pojman, University of Southern Mississippi

Abstract

Small-angle and ultrasmall-angle neutron scattering (SANS/USANS) measurements were used to determine the structural changes induced by photopolymerization of AOT/D(2)O/(dodecyl acrylate) inverse microemulsion systems. Scattering profiles were collected for the initial microemulsions and the films resulting from photopolymerization of the oil phase. The SANS data for the microemulsions were, modeled as spherical, core-shell droplets. Upon polymerization, the clear mircoemulsions formed opaque films. From the SANS/USANS data of the films, it was apparent that this morphology was not preserved upon polymerization; however, it was clearly observed that the formulation of the microemulsion had a large impact on the structure within the films. The Guinier region in the USANS data (2.5 x 10(-5) angstrom(-1) <= Q <= 5.3 x 10(-3) angstrom(-1)) from the films indicates that very large structures are formed. Simultaneously, a well-defined peak (0.15 angstrom(-1) <= Q <= 0.25 angstrom(-1)) in the SANS data indicates that there are also much smaller structures formed. It is proposed that the low-Q scattering arises from aggregation of the nanometer-size water droplets in the microemulsion to form droplets large enough to scatter visible light, while the peak in the high-Q region results from bilayered structures formed by the surfactant.