Shish-Kebob

Extended Chain Crystals and Shish-Kebob Structures... 

Extended chain crystals can be obtained by crystallization under high pressures or under uniaxial extension. So-called shish-kebob structures are frequently observed when crystallizing polymers under orientation, e.g. in stirred solutions and polymer processing from the melt. Similar to lamellae and (micro) fibrils treated in previous chapters, these structures can be routinely visualized and analyzed by AFM. 

Similar to extended chain crystals, the shish-kebob morphology is not observed in samples, which have been subjected to quiescent crystallization conditions. We introduce several examples already in this chapter in order to present a complete cross-section of all levels of structural hierarchy in polymers. Further examples related to oriented crystallization of polymers in practical applications will be the focus of Sect. 3.5. 

The imaging of extended chain crystals, as well as the related shish-kebob structures, can be carried out in CM-AFM and TM-AFM. CM-AFM is the preferred method if the lattice structure is to be analyzed in the same experiment otherwise... 

Fig. 3.25 TM-AFM phase image of PP shish-kebob crystals on sibcon [62]...

TM-AFM is superior due to reduced sample deformation and excellent contrast between amorphous phase and crystal phase in the TM phase images. An example of a, shish-kebob morphology is observed in partially dewetted ultrathin films of polypropylene derivatives grafted onto silicon (Fig. 3.25). 

TM-AFM on Shish-Kebob Morphology in Drawn Polyethylene Copolymers... 

Sporadically, the shish-kebob structures, such as the one shown in Fig. 3.27 can be found. Since intermediate tapping conditions have been chosen (see Chap. 2 for details), the less dissipative phase will appear with a positive phase shift (i.e. bright contrast), while the more dissipative phase will appear dark (less positive phase shift). Clearly the relative contrast of the (crystalline) shish-kebob seen in the TM-AFM phase image is consistent with the simplified theory. 

Fig. 3.27 TM-AFM phase image of shish kebob morphology in oriented elastomeric PE [58]...

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