Developing dual beam methods for the study of polymers

Abstract

The use of a combined Focussed Ion Beam/Environmental Scanning Electron Microscope (FIB/ESEM) offers new possibilities for imaging complex heterogeneous polymeric structures. The use of the focussed ion beam, using positively charged gallium ions in conjunction with a measured ‘defocused’ low energy primary electron beam has permitted milling through the heterostructure to be achieved in a controlled way, exposing the inner structure without introducing significant charge damage into the sample. The use of the Environmental Scanning Electron Microscope for imaging the revealed milled sections has then enabled insulating polymer structures to be imaged without charging problems, despite the absence of a conductive coating. Cross sections of a 900nm thick spun cast film of phase separated polystyrene-polybutadiene blends have been successfully milled and imaged, the results agreeing with previous experiments produced using ultramicrotomy and TEM. In addition, elliptical shaped titanium dioxide particles approximately 220nm in diameter have been dispersed in commercial film forming latices at concentrations between 0 and 100 percent volume. The films have been cast, milled 2μm deep and imaged. Results on the arrangement of titanium dioxide particles in the polymer matrices are presented.