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Substituted with four 3,4,5-tris(alkoxy)benzyl mini-dendrons, azacalix[4]pyridine (1) with the saddle-shaped core is the first liquid crystal (LC) of heteracalixaromatics. Conformational regulation of azacalix[4]pyridine by complexing with the zinc ion leads to a significant change in LC properties.

The liquid-crystalline (LC) phase structures and transitions of a combined main-chain/side-chain LC polymer (MCSCLCP) 1 obtained from radical polymerization of a 2-vinylterephthalate, poly(2,5-bis{[6-(4-butoxy-4'-oxybiphenyl) hexyl]oxycarbonyl}styrene), were studied using differential scanning calorimetry, one- and two-dimensional wide-angle X-ray diffraction (1D and 2D WAXD), and polarized light microscopy. We have found that 1 with sufficiently high molecular weight can self-assemble into a hierarchical structure with double orderings on the nanometer and subnanometer scales at low temperatures. The main chains of 1, which are rodlike as a result of the "jacketing" effect generated by the central rigid portion of the side chains laterally attached to every second carbon atom along the polyethylene backbone, form a 2D centered rectangular scaffold. The biphenyl-containing side chains fill the space between the main chains, forming a smectic E (SmE)-like structure with the side-chain axis perpendicular to that of the main chain. This biaxial orientation of 1 was confirmed by our 2D WAXD experiments through three orthogonal directions. The main-chain scaffold remains when the SmE-like packing is melted at elevated temperatures. Further heating leads to a normal smectic A (SmA) structure followed by the isotropic state. We found that when an external electric field was applied, the main-chain scaffold greatly inhibited the motion of the biphenyls. While the main chains gain a sufficiently high mobility in the SmA phase, macroscopic orientation of 1 can be achieved using a rather weak electric field, implying that the main and side chains with orthogonal directions can move cooperatively. Our work demonstrates that when two separate components, one offering the "jacketing" effect to the normally flexible backbone and the other with mesogens that form surrounding LC phases, are introduced simultaneously into the side chains, the polymer obtained can be described as an MCSCLCP with a fascinating hierarchically ordered structure.

Chiral columns formed by a helical cis-polyphenylacetylene (PPA) derivative P1 are reversibly switched during a phase transition between two chiral columnar phases: the frustrated Φh3D-SL phase containing four chains at low temperature and a hexagonal columnar phase Φh at high temperature, accompanied by a simultaneous conformational change. The helix-helix transition along the PPA backbone during the Φh3D-SL-Φh transition makes the uniaxially oriented P1 capable of reversibly and reproducibly elongating (132 %) upon heating and contracting upon cooling, exhibiting the behavior of a two-way shape actuator. [ABSTRACT FROM AUTHOR]

Homeotropically-aligned main-chain and side-on liquid crystalline elastomer films are prepared by using LC thiol–ene and acrylate systems respectively. Evaluated by laser flash analysis, the room temperature thermal conductivities of these two LCP films in the film normal direction are both dramatically higher than those along the horizontal direction. [ABSTRACT FROM AUTHOR]

Crystal orientation and melting behavior of poly( ɛ-caprolactone) in a diblock copolymer of poly( ɛ-caprolactone)- block-poly(2,5-bis[4-methoxyphenyl]oxycarbonyl)styrene) (PCL- b-PMPCS) was investigated. The degrees of polymerization of the PCL and PMPCS block are 200 and 98, respectively. With the PMPCS in a columnar liquid crystalline phase, the diblock is rod-coil one, which exhibits a lamellar phase morphology with the PCL layer thickness of 15.2 nm. Since the glass transition temperature of PMPCS block is much higher than the melting temperature of PCL, the crystallization of PCL is in a one-dimensionally 'hard' confinement environment. Mainly on the basis of two-dimensional wide-angle X-ray diffraction experiments, we identified the orientation of PCL isothermally crystallized at various crystallization temperatures ( Ts). At high Ts ( T ≥ 10 °C), the c-axis of the PCL crystal is along the layer normal of the microphase-separated sturcture. Decreasing T can result in the tilting of PCL c-axis with respect to the layer normal. The lower the T is, the more the c-axis inclines. Meanwhile, the b-axis of PCL remains perpendicular to the layer normal. At a very low T of −78 °C, the orientation of the PCL crystals is completely random. For the samples isothermally crystallized at T ≤ 10 °C, double melting behavior can be observed. While the low temperature endotherm reflects the melting of the crystals originally formed at the T applied, the high temperature one is associated with the crystals subjected to the process of recrystallization/reorganization upon heating due to the annealing effect. [ABSTRACT FROM AUTHOR]

A novel perylene diimide (PDI) derivative bearing four oligosiloxane chains was synthesized. The phase behavior, self-assembly structure and charge transport characteristic of the compound were elucidated via a sequence of experimental techniques such as UV/Vis and fluorescence spectra, differential scanning calorimetry, polarized optical microscopy, one- and two-dimensional X-ray diffraction as well as time-of-flight experiment. The experimental results reveal that the compound forms liquid crystalline (LC) helical supramolecular structure with two molecules coupled side-by-side in each column stratum at room temperature. Due to this unique structure, efficient charge transport occurs in the LC phase and the electron mobility reaches 1.5 × 10 −3  cm 2  V −1  s −1  at ambient temperature in spite of the large π-stack spacing in the column. [ABSTRACT FROM AUTHOR]

A series of diblock copolymers (PS-b-PBBHCSs) composed of polystyrene (PS) and poly(2,5-bis{[6-(4-butoxy-4′-oxybiphenyl)hexyl]oxycarbonyl}styrene)(PBBHCS) were successfully synthesized via atom transfer radical polymerization,with their chemical structures confirmed by various characterizationtechniques. While PS is a conventional coil polymer, PBBHCS is a novelcombined main-chain/side-chain liquid crystalline polymer (MCSCLCP)which can exhibit hierarchically ordered structures. Small-angle X-rayscattering results show that the diblock copolymers with differentcompositions could present lamellar and rectangular cylinder morphologiesbefore the order–disorder transition. Combining the differentialscanning calorimetry and X-ray scattering results, we find that thePBBHCS block in the confined space of microphase separation is stillable to exhibit its liquid crystalline (LC) structures with the rectangularmain-chain scaffold on the nanometer scale and the side-chain orderingon the subnanometer scale, which is the same as that of the homo-PBBHCS.Therefore, a three-length scale ordered hierarchical structure canbe observed in the system we studied, namely, the microphase separationand the double-length scale LC structure of the MCSCLCP. The LC structureof PBBHCS is more stable in the diblock copolymer than that in thehomopolymer with similar molecular weights. Therefore, not only PS-b-PBBHCS can fabricate more complex hierarchy structurebut also the microphase separation can stabilize the hierarchicalassembly of PBBHCS in the nanodomains. [ABSTRACT FROM AUTHOR]