(667e) Focused Ion Beam Imaging of Highly Dispersed Benzocyclobutene-Maleimide/Layered Silicate Thermoset Nanocomposites

Authors: 
Hampton, E. - Presenter, Tuskegee University
Yoonessi, M. - Presenter, OAI at NASA Glenn Research Center
Dean, D. R. - Presenter, University of Alabama at Birmingham
Vaia, R. A. - Presenter, Wright Patterson Air Force Research Laboratory
Tan, L. - Presenter, U.S. Air Force Research Laboratory
Koerner, H. - Presenter, Air Force Research Laboratory
Wheeler, R. - Presenter, Wright Patterson Air Force Research Laboratory


The advancement of thermoset based nanocomposites depends upon the development of fabrication methods that will provide extensive dispersion of nanoparticles within the thermoset and the development of controllable interfacial chemistry. A general methodology has been used to achieve high dispersion in a high temperature benzocyclobutene-maleimide (BCB-MI) thermosetting polymer. A modified approach, which directly addresses the nanoclay dispersion difficulties of thermosets, resulted in a highly disordered thermoset nanocomposite with little or no agglomeration of individual clay platelets, and most importantly no visible remnants of the initial clay tactoid structure. Specifically, imidazolium based reactive and nonreactive surfactants were used to modify montmorillonite, thus providing the necessary thermal stability as well as the ability to covalently connect the nanoparticle surfactant to the BCB-MI matrix. This ?traditional' organoclay served as the starting point to generate a lightly cross-linked corona of BCB-MI around the montmorillonite through a surface catalyzed solution procedure. The subsequent hybrid montmorillonite was then added to neat BCB-MI resulting in a highly disorderly thermoset nanocomposite, as determined by small angle x-ray diffraction and transmission electron microscopy. The extent of coupling between the organic modifier and matrix (reactive and nonreactive surfactants) had a substantial impact on the mechanical properties and thermal properties. Three dimensional visualization of the extent of the disordered structure of the tactoids and nanoclay layers were studied by slice imaging using focused ion beam (FIB) dual-beam SEM. This novel approach provided understanding of the clay nanostructure in the polymer matrix three dimensionally beyond the traditional two dimensional projection imaging.