Aromatic polymers beam damage

Note that the shapes of the two carbon peaks are quite different in Fig. 6.16. This relates to the different chemical bonding in the two polymers in principle this information can be used in analysis, but it has been shown in PMMA that chemical changes due to electron beam damage rapidly alter the peak structure [339]. For many polymers, the low energy loss region may not contain any distinct features for use in analysis or imaging, but aromatic compounds do have a peak at about 7 eV, which has been used to identify polystyrene in a polystyrene/ polybutadiene / poly(methyl methacrylate) sample [340]. 

The thermotropic polymers used in these studies are all random copolyesters. As has previously been documented for other types of polymers, the presence of aromatic rings and/or conjugated bonds, and the absence of CH2—CH2 and ether linkages yield materials most resistant to beam damage (by processes such as chain scission and cross-linking). The family of thermotropic copolyesters most extensively studied here comprises the following randomly sequenced segments ... 

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