A series of copoly(ester imide)s (CPEIs) was synthesized by the esterification of N,N‘-dodecane-1,12-diylbis(trimellitimide) to two different acetylated diols, 4,4‘-dihydroxybiphenyl and hydroquinone, in varying proportions. On the basis of their compositions, six samples are designated as CPEI(A−F), in which CPEI(A) is a homopolymer having 100% of incorporated 4,4‘-dihydroxybiphenyl and CPEI(F), a homopolymer having 100% of incorporated hydroquinone. The composition ratios of the copolymers are 80/20 (B), 60/40 (C), 40/60 (D), and 20/80 (E). Except for CPEI(F), the five CPEI(A−E)s show enantiotropic liquid crystalline behavior during cooling from the isotropic melt. In all of the samples, highly ordered smectic crystal phases are assumed in the solid state. In the course of structural identification, it has been found that CPEI(A−E)s often exhibit anomalous wide-angle X-ray diffraction (WAXD) fiber patterns:  the smectic layer normal is perpendicular to the fiber direction while the (hk0) reflections exhibit maxima along the meridian. Furthermore, the degree of orientation for the (hk0) reflections is apparently much lower than that of the layer structure. Crystallographic analysis is given to provide a quantitative explanation of experimentally obtained WAXD fiber patterns.

Two liquid crystalline polyethers based on 1-(4-hydroxy-4‘-biphenylyl)-2-(4-hydroxyphenyl)propane and 1,12-dibromododecane and 1,15-dibromopentadecane [TPP(n = 12 and 15)] have been characterized to examine the molecular motion and conformations of the methylene units and mesogenic groups using solid state 13C NMR. The methylene conformations were studied as a function of temperature by the γ-gauche effect in the 13C NMR chemical shift, which depends largely on the C−C conformation under the condition of magic angle spinning. The variable-temperature NMR results on the conformational order of the methylene units may be correlated with the entropy changes in the methylene units that are associated with phase transitions measured by differential scanning calorimetry experiments. Both the entropy change of the methylene units and 13C NMR chemical shift show that in the highly ordered liquid crystalline phases of this series of polyethers, the methylene units play an important role in maintaining the order of these phases.

A series of liquid crystalline polyethers has been synthesized from 1-(4-hydroxy-4′biphenylyl)-2-(4-hydroxyphenyl)propane and R,ω-dibromoalkanes [TPP(n)]. TPP(n)s show multiple phase transitions during cooling and heating. In TPP(n ) 7) bulk and fiber samples, three liquid crystalline phases have been identified: nematic phase and highly ordered smectic F and smectic crystal G phases. The detailed structures and morphology of TPP(n ) 7) thin films (with a thickness ranging from 10 to 100 nm) have been studied by electron diffraction and transmission electron microscopy experiments on three different types of substrates. These include silane-grafted, amorphous carbon-coated, and clean glass surfaces. The development of homeotropic molecular alignment in monodomains has been obtained by using substrates with silane-grafted and amorphous carbon-coated surfaces. Both surfaces can also induce structural ordering in TPP(n ) 7) to form an orthorhombic lateral packing which does not exist in the bulk and fiber samples and has only appeared in TPP(n g 11). This phase has been identified as a smectic crystal H phase. It has been found that the monodomain morphology of the highly ordered smectic crystal phases with the homeotropic molecular alignment depends strongly on the structural symmetry. Furthermore, the silane-grafted surface produces better homeotropic molecular alignment for TPP(n ) 7) than the amorphous carbon-coated surface, with the latter demonstrating a continuous change in the chain director between -30°and +30°. This change in the orientation results in observable striations in the monodomain morphology. The origin of this variation in the chain director may be associated with the fact that the vector normal to the layer of the smectic crystal phases is tilted about 32°away from the molecular direction (58°between the molecular direction and the layer surface). The clean glass surface does not induce orthorhombic packing and only polydomain structures can be found in which an in-plane homogeneous alignment of the chain directors exists. On the other hand, mechanically sheared thin films on glass surfaces show a uniaxial homogeneous molecular alignment.

A main-chain liquid-crystalline polyether has been synthesized from 1-(4-hydroxy-4′biphenylyl)-2-(4-hydroxyphenyl)propane and 1,12-dibromododecane, TPP(n ) 12). In our previous report, the phase structures and phase transitions in bulk TPP(n ) 12) have been identified. In this study, thin film samples of TPP(n ) 12) have been prepared with thicknesses ranging from 10 to 100 nm on amorphous carbon coated substrates. Transmission electron microscopy and electron diffraction observations show that the liquid-crystalline chain molecules possess a tilted homeotropic orientation within monodomains at a structural formation temperature of 180 °C in the smectic F (SF) phase. This is due to the surfaceinduced alignment effect. With increasing isothermal time, the lateral size and thickness of the monodomain increase, indicating that the formation of monodomains is initiated by a uniformly oriented molecular aggregate and is conceptually similar to the nucleation-controlled process of polymer crystallization. The growth stage reveals that large-scale molecular motion is required in order to transfer the chain molecules from an isotropic orientation to a tilted homeotropic structure. Electron diffraction results on the TPP(n ) 12) thin films confirm the phase structures identified in bulk materials. When the thin film samples are quenched from the isotropic melt to lower structural formation temperatures, the samples no longer show the tilted homeotropic molecular orientation. This indicates that the amorphous carbon surface-induced alignment process is sensitive to the type of phase in which the structural formation occurs. It is not possible to access the tilted homeotropic orientation when the molecules have been in an ordered structure higher than the SF phase. In the smectic crystal G phase, molecular mobility along the chain direction can still be expected, which is evidenced by an observation of significant morphological layer thickening during annealing in this phase. The regularity of morphological layers in the different ordered phases is also investigated.

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