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Developing new strategies for controlling polymer conformations through precise molecular recognition can potentially generate a machine-like motion that is dependent on molecular information-an important process for the preparation of new intelligent nanomaterials (e.g., polymer-based nanomachines) in the field bordering between polymer chemistry and conventional supramolecular sciences. Herein, we propose a strategy to endow a helical polymer chain with dynamic spring-like (contraction/expansion) motion through the one-dimensional self-assembly (aggregation/disaggregation) of peripheral amphiphilic molecules. In this developing system, we employed a semi-artificial helical polysaccharide presenting peripheral amphiphilic chlorophyll units as a power device that undergoes contractive motion in aqueous media, driven by strong π-π interactions of its chlorophyll units or by cooperative molecular recognition of bipyridyl-type ligands through pairs of chlorophyll units, thereby converting molecular information into the regulated motion of a spring. In addition, this system also undergoes expansive motion through coordination of pyridine. We anticipate that this strategy will be applicable (when combined with the established wrapping chemistry of the helical polysaccharide) to the development of, for example, drug carriers (e.g., nano-syringes), actuators (stimuli-responsive films), and directional transporters (nano-railways), thereby extending the frontiers of supramolecular science.

One of the fundamental problems in supramolecular chemistry, as well as in material sciences, is how to control the self-assembly of polymers on the nanometer scale and how to spontaneously organize them towards the macroscopic scale. To overcome this problem, inspired by the self-assembly systems in nature, which feature the dynamically controlled self-assembly of biopolymers, we have previously proposed a self-assembly system that uses a dynamic liquid/liquid interface with dimensions in the micrometer regime, thereby allowing polymers to self-assemble under precisely controlled nonequilibrium conditions. Herein, we further extend this system to the creation of hierarchical self-assembled architectures of polysaccharides. A natural polysaccharide, β-1,3-glucan (SPG), and water were injected into opposite "legs" of microfluidic devices that had a Y-shape junction, so that two solvents would gradually mix in the down stem, thereby causing SPG to spontaneously self-assemble along the flow in a head-to-tail fashion, mainly through hydrophobic interactions. In the initial stage, several SPG nanofibers would self-assemble at the Y-junction owing to the shearing force, thereby creating oligomers with a three-way junction point. This unique structure, which could not be created through conventional mixing procedures, has a divergent self-assembly capability. The dynamic flow allows the oligomers to interact continuously with SPG nanofibers that are fed into the Y-junction, thus amplifying the nanostructure along the flow to form SPG networks. Consequently, we were able to create stable, centimeter-length macroscopic polysaccharide strands under the selected flow conditions, which implies that SPG nanofibers were assembled hierarchically in a supramolecular fashion in the dynamic flow. Microscopic observations, including SEM and AFM analysis, revealed the existence of clear hierarchical structures inside the obtained strand. The network structures self-assembled to form sub-micrometer-sized fibers. The long fibers further entangled with each other to give stable micrometer-sized fibers, which finally assembled to form the macroscopic strands, in which the final stabilities in the macroscopic regime were governed by that of the network structures in the nanometer regime. Thus, we have exploited this new supramolecular system to create hierarchical polymeric architectures under precisely controlled flow conditions, by combining the conventional supramolecular strategy with microfluidic science.

Two kinds of polymeric nanoarchitectures, i.e., one-dimensional polymer composites and two-dimensional sheet-like structures, can be created using a semiartificial helical polysaccharide with one-dimensional cavities and peripheral molecular-recognition sites.The creation of precise polymer assemblies at the nanometer scale, which could lead to novel chemical and physical properties, depending on their assembly modes, is of great concern because of their potential applications as fundamental nanomaterials. In particular, much effort has been expended on controlling the alignment of ³-conjugated polymers, expecting the creation of nanowires, circuits, and conductive films. Manipulation of functional polymer chains in a bottom-up manner, however, is still a challenging research subject because of the lack of established strategies. 1Natural polysaccharides have captured intense attention as an abundant material source, applicable for recyclable plastics as well as for biomaterials. We have, so far, demonstrated that helical polysaccharides, ¢-1,3-glucans, have a unique wrapping ability toward hydrophobic polymers to form one-dimensional nanocomposites, where the ¢-1,3-glucans act as manipulators for various guest polymers.2 To further extend this unique wrapping ability of ¢-1,3-glucans, we herein report a novel semiartificial ¢-1,3-glucan (Chl-CUR) that has external molecular-recognition sites based on chlorophyll molecules in addition to the inherent one-dimensional spaces inside the helix (Figure 1). Amphiphilic chlorophyll molecules with dendritic tetra(ethylene glycol) (TEG) units are introduced into the 6-OH groups of curdlan, a type of ¢-1,3-glucan, through selective azidation of the 6-OH groups followed by Cu(I)-catalyzed coupling between the azide groups and terminal alkyne attached to the 3¤-position of chlorophyll. It is expected that the attached chlorophyll molecules would be arranged on the curdlan surface in a regular fashion, thereby providing unique ³ spaces for precise polymer recognition.It is already known that natural ¢-1,3-glucans adopt a triplehelical structure in water but dissociates into single chains in DMSO. To investigate whether Chl-CUR also undergoes similar interpolymer transformations as a result of changing water/ DMSO compositions, distilled water was gradually added to a DMSO solution containing Chl-CUR (0.046 mg mL ¹1). Chl-CUR shows characteristic sharp peaks in DMSO at 429 and 654 nm assignable to the Soret and Q y bands of the chlorophyll moiety, suggesting that Chl-CUR dissociates into single chains in DMSO. Upon addition of water, a significant hypochromic effect and slight red shifts, as shown in Figure 2a, were observed in the UVvis spectra, which is indicative of aggregation of chlorophyll units through strong ³³ stacking interactions. On the basis of our previous papers, the CD intensity of Chl-CUR is expected to increase when it adopts a triple-helical structure in water.3 However, as revealed in Figure 2b, the CD intensity gradually decreased with increasing water co...

Side milling tests of CFRP (carbon fiber reinforced plastics) containing thermosetting resin are carried out by TiAlN/AlCrN-coated, H2-free DLC (diamond-like carbon)-coated, and CVD diamond-coated carbide end mills without coolant. Two types of end mills having different helix angles of 30° and 60° are used. The film thickness and surface smoothness are varied for the DLC-coated end mills. The cutting characteristics are evaluated by tool wear and surface integrity (i.e., 3D profiles of the machined surface, generation of fluffing, delamination, and pull-out of the carbon fibers). The cutting force and tool flank temperature are also examined for the two types of CFRP composites and the helix angle of the end mill. “Inclination milling,”in which the end mill is tilted so that the resultant cutting force acts parallel to the work surface, is proposed as a novel technique to be used with a high-helix angle end mill. This unique approach enables the reduction of tool wear and improves the surface integrity of machined CFRP surfaces.