Morphology of the Zigzag Forms

MORPHOLOGY OF THE ZIGZAG FORMS 9.3.1 Crystal Structure of the a Form... 

Various types of morphologies and crystalline modifications of s-PS have been reported [44], One of these modifications has an orthorhombic form (space group = P2i2i2i) with a planar zigzag conformation of back-bone chain. This form corresponds to the a-phase found by Kobayashi et al. [35] and to the P-phase named by Guerra et al. [36], The crystal structure of this form was analyzed and the plane of phenyl rings within this form is normal to the chain axis (c-axis) [37-39],... 

The potential for novel phase behaviour in rod-coil block copolymers is illustrated by the recent work of Thomas and co-workers on poly(hexyl iso-cyanate)(PHIC)-PS rod-coil diblock copolymers (Chen etal. 1996). PHIC, which adopts a helical conformation in the solid state, has a long persistence length (50-60 A) (Bur and Fetters 1976) and can form lyotropic liquid crystal phases in solution (Aharoni 1980). The polymer studied by Thomas and co-workers has a short PS block attached to a long PHIC block. A number of morphologies were reported—wavy lamellar, zigzag and arrowhead structures—where the rod block is tilted with respect to the layers, and there are different alternations of tilt between domains (Chen et al. 1996) (Fig. 2.37). These structures are analogous to tilted smectic thermotropic liquid crystalline phases (Chen et al. 1996). 

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