Volume 50 Issue 8, August 2018

This review focuses on the recent developments on the photo-induced liquefaction and softening of azobenzene-based materials. The trans–cis photoisomerization of azobenzene units incorporated in molecular materials, polymers, and gels induces a variety of state changes such as solid–liquid, gel–sol, and glass–rubber transitions of those materials isothermally. Several novel applications such as reusable and environmentally friendly photoresists, reworkable adhesives, and self-healing materials can be expected using the photochemical liquefaction and softening.

Recent works revealed that protein and cell resistance of bioinert self-assembled monolayers originates in the physical barrier of the interfacial water. We review the history of the previous works that attempted to clarify the underlying mechanism and discuss prospects to apply the findings to design new biomaterials.

Synthesis and thermal properties of poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s with regulated regio- and stereochemistry are described. Pd complexes with diimine ligands promote controlled isomerization polymerization of 4-alkylcyclopentenes and alkenylcyclohexanes to afford poly(oligomethylene-1,3-cyclopentylene)s with trans structure and poly(oligomethylene-1,4-cyclohexylene)s with trans or cis structure, respectively. Poly(ethylene-1,2-cyclopentylene) with cis and trans-stereochemistry can be obtained by Fe- and Co-catalyzed cyclopolymerization of 1,6-heptadiene, respectively. The thermal properties of the poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s are compared to those of previously reported polymers with different regio- or stereochemistry.

In this focus review, our recent investigations into the deformation and fracture processes of crystalline polymers using coarse-grained molecular dynamics simulations are described. The lamellar structure of polyethylene, a fundamental structural feature of this polymer, is successfully reproduced. Then, a stress– strain curve that exhibited good consistency with that observed experimentally is obtained. Molecular simulations are a powerful tool for elucidating the mechanisms of the deformation and fracture processes of crystalline polymers at the molecular level and this review will contribute to the development of this field of research.

This review summarizes the recent advances in surface-coated single-walled carbon nanotubes as near-infrared nanometer-sized photoluminescent emitters for single-particle imaging and tracking applications in complex biological environments. It is focused on demonstrating surface coating identification, excitation strategies comparison, and long-term single-nanotube tracking inside the brain extracellular space in the live brain tissue.

Open-shell organic semiconductors are poised to enable new functions and applications ranging from electronics and optoelectronics to magneto-electronics. Here, we review strategies toward molecular magnets or spin–polarized magnetic organic semiconductors that encompasses incorporation of stable radical groups directly into the backbone of organic semiconductors or preparation of highly conjugated ladder-type molecules based on open–shell Kekulé–type structures to enable efficient spin delocalization/spin-transfer along the conjugation length. We briefly survey the history of this field, summarize recent developments, and set an outlook for the future.

A recent progress of phenanthro[1,2-b:8,7-b′]dithiophene (PDT)-based low bandgap semiconducting polymers combined with various strong acceptor units are described. By incorporating a highly π-extended PDT core into the polymer backbone, the synthesized polymers have deep HOMO energy levels and formed a dense packing structure with a short π-stacking distance. The PDT-based polymers with optimal side chains and high molecular weight exhibit high hole mobility of up to 0.18 cm⁻¹ V⁻¹ s⁻¹ in organic field-effect transistors and high power conversion efficiency over 6%. These results indicate that PDT is a good π-framework as high-performance semiconducting polymers.

Amphiphilic C₃-symmetric tris-ureas self-assemble into supramolecular hydrogels in aqueous solution. These supramolecular hydrogels were used as matrices for the electrophoresis of biopolymers (SUGE: SupramolecularGelElectrophoresis). A unique separation mode in comparison to that of SDS–PAGE was found during the electrophoresis of denatured proteins. Native proteins were separated on the basis of their isoelectric points and retained their activities. Large DNA fragments that previously had been separated only by pulsed-field gel electrophoresis were separated using a supramolecular hydrogel matrix and a typical continuous-field electrophoresis apparatus.

We reviewed the recent progress in the development of micro/nanofibrillar scaffolds for biomedical applications. We demonstrated the significance and essential information on four different micro/nanofibrillar scaffolds: (1) solid micro/nanofibrillar scaffolds (2) hydrogel nanofibrillar network scaffolds based on bacterial cellulose, (3) hydrogel micro/nanofiber scaffolds based on partially precipitated PVA, and (4) hydrogel micro/nanofiber scaffolds based on cross-linked PVA. This review would guide researchers for selecting a proper scaffold suitable for their own purposes and developing more sophisticated scaffolds.

Self-assemble introduction of α-glucan contained block copolymer materials into the particular layer of the memory devices have been impressed by their excellent performance. Some newly reported MH-based copolymer literatures in electronic application are discussed in this focus review, including the electron-trapping mechanism of oligosaccharide MH, the relationships between chemical structures and their supramolecules, self-assembly morphologies and the memory device characteristics of electronic devices. As a perspective, the glucose-based block copolymer materials have a great potential to develop into the greener generation for advanced green electronics.

Recent developments for nanowires fabricated from self-assembled π-conjugated polymers are reviewed. Particular attention is paid to advances in techniques for scalable production of highly ordered nanowires as well as their deposition and alignment in thin films and composites. The benefits of using π-conjugated polymer nanowires, rather than thin films, in electronic devices is examined. Devices investigated include organic field-effect transistors (OFETs), chemical sensors, and thermoelectric devices.

The facile control of the microdomain orientation in the liquid-crystalline block copolymer (LC-BCP) thin films has been realized by means of micropore extrusion and introducing polydimethylsiloxane (PDMS), instead of complicated processes or costly apparatus. In extrusion process, the alignment can be recovered via ultrasonicating the extruded BCP solution or as-placing upon long-time thermal annealing.

The true chiroptical measurements of optically anisotropic samples cannot be generally achieved with modern chiroptical spectrophotometers such as circular dichroism and circularly polarized luminescence based on polarization modulation techniques because of the coupling effect of the nonideal optics and the electronics with macroscopic anisotropies. Artifact signals related to the nonchiral phenomena are often much stronger than the chiroptical signals. Universal chiroptical spectrophotometer (UCS) and comprehensive chiroptical spectrophotometer (CCS) integrated into the Stokes–Mueller matrix analysis for optically anisotropic samples can be applicable for accurate chiroptical measurements for samples with macroscopic anisotropies.

A chromatography-free procedure for the preparation of monodisperse monotosylated PEGs allowed for the preparation of 8- to 16-mers in relatively large quantities in good yields and purities and facilitates the investigation of PEG-based functional molecules such as structured PEGs, which had specific two-dimensional shapes. For example, the triangular molecule dehydrated at a lower temperature than linear compounds with a similar molecular weight and can suppress aggregation of proteins at high temperatures. It was also found that the introduction of an aromatic group in the PEG skeleton lowered the dehydration temperature.

Intracellular structures and function are tightly interwoven. Recapitulation of such intracellular microenvironments may enable novel biomimetic material synthesis and bioanalysis. Cell-inspired microanalysis platforms can be constructed by combined top-down microfabrication and bottom-up molecular self-assembly. Microcompartments of phase-separated aqueous solutions also play a critical role in biological processes. The biphasic microdroplets provide a unique analytical platform that conventional homogeneous bulk environments fail to achieve.

A new nucleic acid delivery framework, predicated on a photo-responsive cationic block copolymer (BCP), was used to precisely tune nucleic acid binding and provide spatiotemporal control over gene expression. This innovative platform leveraged a macromolecular design in which the polymer moieties directly responsible for nucleic acid complexation were cleaved from the polymer upon photo-stimulation, significantly enhancing nucleic acid release. Temporal control over polyplex disassembly facilitated development of a potentially universal, kinetic modeling scheme for gene silencing. Furthermore, this versatile BCP-based framework easily accommodated anionic excipients and quantum dot imaging constructs.

The inclusion of electrically insulating aliphatic spacers between π-conjugated segments of semiconducting polymers represents an emerging and versatile tool to control material properties. Here we review this strategy and highlight recent reports demonstrating the control over chain self-assembly, the tunability of viscosity and elasticity, and the ability to provide insights into inter- and intra-charge transport processes—without detrimental effects on the polymer semiconducting ability. While still at an early stage, this approach gives promise towards engineering optoelectronic performance, melt-processed organic electronics, and applications toward stretchable wearable semiconducting devices.

A novel concept for cellular scaffolds with 2D-patterned mechanical properties was proposed. Thin films of glassy polystyrene (PS) with thicknesses ranging from 100 nm to 1 μm were prepared on epoxy resin-based line and space (L&S) patterned substrates. Although the outermost surface of PS was sufficiently flat regardless of the L&S patterned substrates, the mechanical responses differed depending on the presence of the underlying resin foundation. The initial cell adhesion and spreading and the proliferation on the scaffolds were affected by the 2D-patterned mechanical properties.

Amyloid ß-protein (Aß) is converted to toxic forms through interactions with the ganglioside in neuronal membranes. The highly ganglioside-enriched microdomain (ganglioside cluster) in neuronal membranes plays a key role in Aß assembly. In the present study, lipid components of synaptosome extracted from mouse aged brain was determined by LC-MS spectroscopy. We demonstrated that ganglioside ratio (GM3 to GM1) and cholesterol content are an important factor for inducing Aß assembly. These results provides important insight into the mechanism of polypeptide assembly on the neuronal membrane in Alzheimer’s disease patients.

The alignment of azobenzene molecule was induced by a new-alignment-patterning technique based on a scanning wave photopolymerization (SWaP) concept with unpolarized light. This finding indicates that SWaP could be employed as a novel and simple fabrication process for preparing a wide variety of highly functional optical devices requiring alignment control.

Liquid-crystalline Au complexes with siloxane groups at the termini of flexible chains were synthesized. The effects of the molecular and molecular aggregate structures on the luminescence behavior of the complexes were investigated. In condensed phases, different luminescence colors were observed depending on the aggregate structure due to the effect of intermolecular interactions; thus, the luminescence color of the Au complexes can be controlled by the intermolecular interactions based on the structure of the molecular aggregates.

To a thermocell consisting of the redox pair of ferrocenecarboxylate/ferroceniumcarboxylate was added β-cyclodextrin as host matrix. The Seebeck coefficient increases to −1.20 mV/K by the host–guest interaction between ferrocenecarboxylate and β-CD.

Polymer chain conformation was utilized to control the nucleation of a cholesterol-pyridine molecular gel. Collapsed chain conformations influence gel structure and dissociation behavior by acting as physical barriers that lead to confinement effects and permanent networks. An extended polymer chain conformation allowed for polymer–molecular-gel interactions and increased dissociation temperatures due to its highly ordered structure, resulting in transient networks. Additionally, the high molecular weight polymer solution behavior guided solution mechanics, where collapsed chains lead to viscous solutions and gels and extended chains led to elastic gel networks.

A series of amphiphilic block oligomers were designed and synthesized using ruthenium-catalyzed living radical polymerization with poly(ethylene glycol) and butyl methacrylates (BMA). These PEGylated oligomers showed high binding efficiencies for liposomal preparations as model cell membranes, and also had low cytotoxicity. BMA contents and monomer sequences in the copolymers strongly affected their binding efficiencies. Current method enabled precise control of the primary structures of amphiphilic oligomers, allowing tuning of their binding efficiencies. These amphiphilic block oligomers have promise as novel membrane anchors for many biomedical applications.

Cellulose oligomers were synthesized via cellodextrin phosphorylase-catalyzed reactions using α-D-glucose 1-phosphate monomers and D-glucose primers. The products prepared at relatively high primer concentrations self-assembled into highly grown nanoribbon network structures. The nanoribbons were composed of cellulose oligomers with degree-of-polymerization (DP) values of 8-9 with certain degrees of DP distribution and displayed the cellulose II allomorph. A formation mechanism for the unique nanostructures was proposed based on analyses of reaction time-dependent differences of the product solutions.