Microstructure of Amorphous and Semi-Crystalline Polymers.
Final rept. Feb 77-Oct 80,
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MATERIALS SCIENCE AND ENGINEERING
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Work was carried out under this grant has led to the development of a technique for scanning transmission electron microscope of polymers which seems to offer outstanding promise for the characterization of their structures. When applied to amorphous thermoplastics, the structures are found to be homogeneous down to the limit of resolution to the microscope, with no evidence found for the presence of nodular features or other structures characteristic of regions of local order in the materials. This finding is in accord with the results of small angle neutron scattering studies of same materials. Based on the combined results of these studies, it is suggested that the nodular hypothesis be laid to rest and that the structure of flexible chain amorphous polymers be represented by models such as the random coil. The technique of microtoming bulk samples followed by staining with heavy metal atoms and viewing with Z contrast in the scanning transmission electron microscope has also been used with success to characterize the structures of epoxy and polyimide resins. Commercial polyimide films have been shown to be homogeneous on a scale of 50-200 Angstroms with the scale and form of the heterogeneities varying through the thickness of the film. The structure of epoxy resins presents a more complicated issue.