Phase Identification in a Series of Liquid-Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structures. 4. Phase Structures and Order Evolution in TPP(n = 12) Thin Films

Abstract

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.

Processing-Dependent Lamellar Polymorphism of Hyperbranched Liquid-Crystalline Polymer with Variable Light Emission

“…Like that in the HLCP powder, such a large interlamellar spacing may indicate a bilayer tilted smectic structure, but the emission wavelength around 500 nm resembling that in spin-coated HLCP film pointed to offset packing of the CS luminogens. However, the appearance of several scattering peaks in the wide-angle region was indicative of the formation of a highly ordered crystal-like smectic G (SmG) phase (Figure S16), which has additional periodic ordering between the layers in comparison to the SmF analogue formed by HLCP . We thus come to a preliminary conclusion that it is because the highly branched topological architecture of the HLCP that facilitate such an interesting processing-dependent behavior to control the assembled structures and fluorescence colors.…”

Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structures. 7. Phase Structures in a Series of Copolyethers Containing Odd and Even Numbers of Methylene Units of Different Compositions

“…Furthermore, TPP( m = 12) possesses two crystalline phases, K 1 and K 2 , which do not exist in TPP( n = 7). The transition thermodynamic properties (temperatures and heats of transitions) are also different in these TPPs. − Molecular dynamics in different phases, surface-induced phase structures, , and structural and morphological development in TPPs 8,9 have also been investigated.…”

Extended Chain Lamella Formation Characteristics of Main-Chain Smectic Liquid Crystalline Copolyesters Comprising Different Length Units

“…The SmI phases of PB- n polyesters exhibited SAXS maxima that are ascribed to stacked chain-folded lamellae; the spacing increased with annealing in the SmI phase, suggesting that the SmI LCs tend to eliminate chain folding by chain-sliding diffusion . Similar thickened lamellae, composed of almost completely extended polymer chains, have been observed for a TPP polyether annealed in a SmF phase . Thus, chain-sliding diffusion and the elimination of folding require two-dimensional hexagonal packing of the lateral chains, as in the SmI and SmF phases.…”

“…22 Similar thickened lamellae, composed of almost completely extended polymer chains, have been observed for a TPP polyether annealed in a SmF phase. 23 Thus, chain-sliding diffusion and the elimination of folding require two-dimensional hexagonal packing of the lateral chains, as in the SmI and SmF phases. The rate of chain-sliding diffusion can be increased by decreasing the smectic layer order, i.e., the positional order along the chain axis.…”