Thermotropic Liquid Crystals of Main‐Chain Polyesters having a Mesogenic 4,4′‐Biphenyldicarboxylate Unit, 14

Abstract

Summary: Anisotropy in molecular motions of a glassy smectic CA (SmCA) liquid crystal of a main‐chain BB‐5(3‐Me) polyester was examined by dynamic mechanical analysis (DMA) for fibrous monodomain samples with two distinct orientations of smectic layers perpendicular and parallel to the fiber axis. The α‐process attributed to micro‐Brownian motion of the polymer on the glass transition shows clear anisotropy explainable by the nature of the smectic layer structure. Time‐temperature superposition is applicable to the α‐process, so that the frequency of the micro‐Brownian motion in the SmCA phase can be estimated despite the narrow frequency range in DMA. The results suggest that the decoupling of the molecular motions in two characteristic directions are parallel and perpendicular to the layer. The amplitude of the micro‐Brownian motion in the layer normal direction is 3 times smaller than that in the layer direction, and the frequency in the layer normal direction is 2.5 times higher than that in the layer direction.Illustration of molecular packing structures: fiber A (left side) and fiber B (right side) with the orientations of polymers parallel and perpendicular to the fiber, respectively.imageIllustration of molecular packing structures: fiber A (left side) and fiber B (right side) with the orientations of polymers parallel and perpendicular to the fiber, respectively.

Stress Response and Deformation of Block Copolymer Lamellae on Stretching in Normal Direction: Effects of Lateral Size of Lamellae

“…The differential scanning calorimetry (DSC) curve measured upon heating at a rate of 10 °C min −1 included a sharp increase in heat capacity and an endothermic peak, which were attributed to the glass transition and isotropization, respectively, of the smectic LC formed by the BB‐5(3‐Me) segment. [ 22,23 ] The glass transition temperature ( T g ) of the PEMA measured for homo PEMA was 70 °C, although the T g of the PEMA block was barely detected, likely due to the smaller PEMA fraction in the copolymer. [ 16 ] Table 1 summarizes the characterization of the copolymers.…”

Several Interesting Fields Exploited through Understanding of Polymeric Effects on Liquid Crystals of Main-Chain Polyesters

“…The resulting solid is hence regarded as liquid crystal glass. 18,23,24,[65][66][67][68][69][70][71][72][73][74][75][76][77][78] While conventional glass, namely isotropic liquid glass, is characterized by an absence of long-range order, the nematic LC glass possesses a simple orientational order of rod-like molecules and the smectic LC glass has the long-range one-dimensional positional order as well. These LC glasses are thus expected to provide new insight into dynamics of glassy materials representing a topic of current interest in condensed matter physics.…”

“…The glass transition in the smectic LC is attributable to the freezing of translational molecular motion within the layer. 18,24 This seems to be the reason why T 0 LC corresponds to T 0L iso . …”

Effect of molecular weight on microcrystalline structure formation in polymer with perylenediimide side chain

“…(a)]. In general, the main chain orients parallel to the flow direction when fiber samples were spun from isotropic melt . The PDI units in PAc12PDI keeps aggregations via strong π–π interaction even in diluted solution state, which cannot be observed in Ac12PDI monomer (Supporting Information Fig.…”