3.3.2. Architecture effects
The grafting of rigid or semi-flexible blocks, segments or mesogens as side chains or main chain extensions, can lead to richer and more complex morphologies. The use of comb-type architectures with pendant flexible or rigid moieties emanating from a main soft backbone is a common pathway to increase the morphological complexity in block copolymers. The resulting polymers usually possess high chain rigidity and liquid crystalline nature, depending on the length and the chemical structure of the side chains.
The potential of pendant oligomers to construct functional organized materials was demonstrated by Hayakawa and Horiuchi [118], who created extremely regular hierarchical structures from low polydisperse copolymers of coiled PS blocks with a semi-rod POTI (isoprene with oligothiophene-modified side chains). The SEM images of the polymer film cast from CS2 solution showed single layers of hexagonally packed micropores with a narrow size distribution (Fig. 25). They demonstrated the characteristics of a liquid-crystalline smectic mesophase on the π-stacked rod blocks. Annealing changed the direction of the cylinders from perpendicular to parallel at the bottom of the film, while the upper side of the film remained the same.