Lattice bending in electrooptically active poly(nonylbithiazole) and poly(nonylbisoxazole)

The similar to2.4 nm (100) lattice planes of electrooptically active poly(nonylbithiazole) (PNBT) and poly(nonylbisoxazole) (PNBO) crystallites have been imaged by means of low-dose high-resolution transmission electron microscopy (HRTEM). The average dimensions of the observed crystallites were (14 +/- 9) x (13 +/- 6) nm (width vs length) and (80 +/- 36) x (22 +/- 9) nm for PNBT and PNBO, respectively. Atomization of dilute polymer solutions led to the formation of discontinuous thin films containing numerous holes. The influence of these surfaces on the crystallization process was evident in the preferential parallel orientation of the (100) fringes with respect to the film edges. Evidence of considerable lattice bending about the [010] (pi-pi stacking) direction was observed in both compounds. Two-dimensional maps of the local lattice curvature revealed substantial differences in the modes of deformation of the two polymers: PNBT crystallites curved in a continuous fashion, whereas PNBO crystallites localized the distortions. Possible factors that could influence the observed deformation mechanisms are discussed.