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A linearly polarized laser beam was used to control nanocylinders self-assembled in an amphiphilic diblock liquid-crystalline copolymer consisting of flexible poly(ethylene oxide) as a hydrophilic block and poly(methacrylate) containing an azobenzene moiety in the side chain as a hydrophobic liquid-crystalline segment. The perfect array of poly(ethylene oxide) nanocylinders was achieved, aligned perpendicularly to the polarization direction of the actinic light by supramolecular cooperative motions between the ordered azobenzene and microphase separation. By the simple and convenient way of photocontrol, the macroscopic parallel patterning of nanocylinders can be easily obtained in an arbitrary area.

Molecular iodine has been introduced into the alkali lignin (AL) solutions to adjust the π-π aggregation, and the effect of lignin-iodine complexes on the aggregation and assembly characteristics of AL have been investigated by using fluorescence, UV-vis spectroscopy, light scattering, and viscometric techniques. Results show that AL form π-π aggregates (i.e., J-aggregates) in THF driven by the π-π interaction of the aromatic groups in AL, and the π-π aggregates undergo disaggregation in THF-I(2) media because of the formation of lignin-iodine charge-transfer complexes. By using iodine as a probe to investigate the aggregation behaviors and assembly characteristics, it is estimated that about 18 mol % aromatic groups of AL form π-π aggregates in AL molecular aggregates. When molecular iodine is introduced into the AL solutions, lignin-iodine complexes occur with charge-transfer transition from HOMO of the aromatic groups of AL to the LUMO of iodine. The formation of lignin-iodine complexes reduces the affinity of the aromatic groups approaching each other due to the electrostatic repulsion and then eliminates the π-π interaction of the aromatic groups. The disaggregation of the π-π aggregates brings a dissociation behavior of AL chains and a pronounced molecular expansion. This dissociation behavior and molecular expansion of AL in the dipping solutions induce a decrease in the adsorbed amount and an increase in the adsorption rate, when AL is transferred from the dipping solution to the self-assembled adsorbed films. Consequently, the adsorption behavior of AL can be controlled by adjusting the π-π aggregation. Above observations give insight into the occurrence of J-aggregation of the aromatic groups in the AL molecular aggregates and the disaggregation mechanism of AL aggregates induced by the lignin-iodine complexes for the first time. The understanding can provide an academic instruction in the efficient utilization of the alkali lignin from the waste liquor and also leads to further development in expanding functionalities of the aromatic compounds through manipulation of the π-π aggregation.

Liquid-crystalline polymers (LCPs) have been extensively studied as advanced functional materials because of their useful properties, such as their self-organizing nature, the fluidity of long-range order, their cooperative motions, and their anisotropy in various physical properties.[1] The combination of LCPs with microphase-separated block copolymers has given the designed materials some interesting features. [2][3][4] Furthermore, periodic nanostructures may be formed by the interplay processes between the microphase separation and the regular periodicity of LC ordering, [5,6] which are known as supramolecular cooperative motions (SMCMs). It is widely known that ordered microphase structures can be formed in well-defined block copolymers, [7][8][9][10][11][12][13][14][15][16] which can be used as templates for the fabrication of novel nanostructured materials. Unfortunately, perfect domain order over a large area cannot be achieved by molecular self-assembly alone. Recent progress in block copolymers has concentrated on the control of such microphase-separated structures on a macroscopic scale: electric or magnetic-field, [7][8][9] temperature-gradient, [10] crystallization, [11] modified-substrate-surface, [12,13] shearing, [14] solvent-evaporation, [15] and roll-casting [16] methods have been explored for obtaining long-range order. Although introduction of LC ordering to act on the microphase-separated structures might provide a new opportunity to control nanoscopic ordered structures, SMCMs have not yet been adopted as a control method. Here, we report a simple rubbing technique combined with the SMCMs to align three-dimensional nanocylinder phase domains in an amphiphilic diblock LC copolymer. As shown in Figure 1, an amphiphilic diblock LC copolymer consisting of poly(ethylene oxide) (PEO) and polymethacrylate (PMA) containing an azobenzene (Az) moiety in the side chain, PEO 114 -b-PMA(Az) 51 , was used to study the microphase-separated structures. Typical transmission electron microscopy (TEM) images of annealed copolymer films without rubbing treatment show nanocylinders aligned perpendicular to the film surface with a diameter of 10 nm, dispersed in an Az LC matrix with a periodicity of 24 nm (Fig. 1B).A mechanical rubbing method, one of the most popular techniques for aligning LCs, has been used to control lowmolecular-weight compounds, LC polymers, and cross-linked LC gels. [17,18] Here, we first used this method combined with SMCMs to manipulate nanostructures of the amphiphilic diblock LC copolymer. Copolymer films with a thickness of about 200 nm were treated by a rubbing technique, as shown in Figure 1C. After annealing, a large anisotropic absorption was observed in the polarized UV-vis spectra shown in Figure 2A, indicating that the homogeneous LC alignment was achieved parallel to the rubbing direction. An order parameter (S) of 0.57 was obtained at 332 nm from Equation 1:where A ʈ and A ⊥ are the absorbance parallel and perpendicular to the rubbing direction, respectively. Such highly orde...

To take full advantage of sunlight for photomechanical materials, NIR-vis-UV light-responsive actuator films of polymer-dispersed liquid crystal (PDLC)/graphene oxide (GO) nanocomposites were fabricated. The strategy is based on phase transition of LCs from nematic to isotropic phase induced by combination of photochemical and photothermal processes in the PDLC/GO nanocomposites. Upon mechanical stretching of the film, both topological shape change and mesogenic alignment occurred in the separated LC domains, enabling the film to respond to NIR-vis-UV light. The homodispersed GO flakes act as photoabsorbent and nanoscale heat source to transfer NIR or VIS light into thermal energy, heating the film and photothermally inducing phase transition of LC microdomains. By utilizing photochemical phase transition of LCs upon UV-light irradiation, one azobenzene dye was incorporated into the LC domains, endowing the nanocomposite films with UV-responsive property. Moreover, the light-responsive behaviors can be well-controlled by adjusting the elongation ratio upon mechanical treatment. The NIR-vis-UV light-responsive PDLC/GO nanocomposite films exhibit excellent properties of easy fabrication, low-cost, and good film-forming and mechanical features, promising their numerous applications in the field of soft actuators and optomechanical systems driven directly by sunlight.

Swimmers at liquid/air interfaces have drawn enormous attention because of their potential applications. Described herein is one novel light-driven swimmer based on ab imorph composite structure of ap hotoresponsive liquidcrystalline polymer network and ac ommercially available polyimide (Kapton). The motion of the swimmer can be controlled by photoirradiation. The bilayer-structured film shows quickly photoinduced bending towards the Kapton side upon exposure to UV light, and recovers immediately after removal of light. When placed on aliquid surface,the swimmer propels itself continually though rhythmic beating the liquid like ad olphin moving forward with its tail fin. Besides,l ightpowered rotation of the swimmer is successfully achieved by simply changing the length-width ratio and the irradiation site, mimicking the function of adolphinspectoral fin. Combining the forward movement and rotation motion together,o ndemand directional control of the photo-driven swimmer can be readily obtained at room temperature,showing promise for miniaturized units for transportation.

Self-assembly, as a typical bottom-up strategy for the fabrication of functional materials, has been applied to fabricate chiral materials with subtle chiral nanostructures. The chiral nanostructures exhibit great potential in asymmetric catalysis, chiral sensing, chiral electronics, photonics, and even the realization of several biological functions. According to existing studies, the supramolecular chirality transfer process combined with hierarchical self-assembly plays a vital role in the fabrication of multiscale chiral structures. This progress report focuses on the hierarchical self-assembly of chiral or achiral molecules that aggregate with asymmetric spatial structures such as twisted bands, helices, and superhelices in different environments. Herein, recent studies on the chirality transfer induced self-assembly based on a variety of supramolecular interactions are summarized. In addition, the influence of different environments and the states of systems including solutions, condensed states, gel systems, interfaces on the asymmetric hierarchical self-assembly, and the expression of chirality are explored. Moreover, both the driving forces that facilitate chiral bias and the supramolecular interactions that play an important role in the expression, transfer, and amplification of the chiral sense are correspondingly discussed.

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