*3.4. Microscopy (SEM)*

Figure 14 shows the cross-sections of the outer regions of the tensile fractured surfaces of the PET layered WG materials. Notable is the "intact" interface between the WG and the PET layer in the Ground sample. In the Brushed sample, the cross-section was rougher than that of the Ground sample, indicating a less brittle sample in accordance with the tensile properties given in Table 1. Contrary to the Ground sample, a damaged interface could be seen in the Brushed sample. This observation corroborates the results of the cross-sectional nanoindentation, contact angle, and WVTR tests. Due to the better interfacial bonding of the PET to the WG polymer in the Ground sample, it had higher interfacial hardness and better water vapor barrier properties. Moreover, the PET layer in the Ground sample seemed to retain its structural integrity during fracture whereas the same in the Brushed sample was lacking. The PET layer in the latter exhibited extensive cracks. This was the

result of the direct contact of the PET layer with the diamine, which caused aminolysis of the PET (see Section 3.5). Consequently, the Brushed sample had inferior barrier properties when compared to the Ground sample.

**Figure 14.** SEM micrographs of the tensile fractured surfaces.
