Articles in 2016

The crystalline phase of PVDF film prepared by spin-coating changes both of the polymer–solvent interaction and the evaporation rate. In the much solvent remained state, the crystalline phase changes in the order of α, γ and β phase with increasing the dipole moment of solvent. In the solvent-evaporated state, the crystalline phase of PVDF and solvent with higher dipole moment system changes in the order of β, γ and α phase with increasing the solvent evaporation rate, whereas the PVDF and solvent with lower dipole moment system forms into α phase regardless of the evaporation rate.

Angle-independent colored materials based on Christiansen effect was successfully prepared using phase-separated polymer membrane and thermotropic liquid crystal. Because this system displays angle-independent color and can act as a multi-color polymer-dispersed liquid crystal, I believe that this system may be applicable for energy-saving multi-color displays.

We demonstrate a new methodology of DNA and RNA functionalization with a base surrogate prepared from d-threoninol. With this surrogate, we can introduce functional molecules at any position in the sequence. Our methodology is conceptually similar to copolymerization; phosphoramidite monomers of base surrogates, and natural nucleotides are ‘copolymerized’ on solid supports to prepare functional oligonucleotides. The incorporation of intercalating moieties allows for the design of four stable functional motifs: wedges, interstrand-wedges, dimers and clusters. By selecting suitable functional molecules and motifs, we can design novel photofunctional oligonucleotides.

A green method for the synthesis of ‘artificial urushi’ has been developed using cardanol, a main ingredient of cashew nutshell liquid, as the monomer via a reaction mimicking that of natural urushi. A water-in-cardanol (w/o) emulsion was developed by identifying a novel emulsifier, and polymerization of the cardanol emulsion generated prepolymer films, leading to polycardanol (artificial urushi) after curing with mechanical properties that are approximate to those of natural urushi coatings.

In this focus review, alternating copolymers of carbon dioxide with epoxides have been synthesized and studied as novel ion-conductive polymers. The Li salt electrolytes of poly(ethylene carbonate) (PEC) and of other polycarbonates having different side groups exhibited remarkable ion-conductive properties including the following: increased conductivity with increasingly higher salt concentrations, very high values for the Li⁺ transference number, and good electrochemical stability. The Li-ion conductivity of a highly concentrated PEC-LiFSI electrolyte was estimated to be greater than 10⁻⁴ S cm⁻¹, and excellent battery performance was demonstrated at room temperature.

Time evolution behavior is described for a transient network formed via hydrogen bonds in a random copolymer of vinyl acetate and vinyl alcohol. As the cross-link density depends on temperature, the storage modulus G′ of the system slowly evolves toward equilibrium at the experimental temperature, T_a, after changing the temperature from higher or lower than T_a. The ‘memory effect’ (the structure developed at a certain temperature is preserved after changing the temperature) found in the system is discussed in detail.

Self-healable gel was designed by end-crosslinking of controlled telechelic polymer carrying a trithiocarbonate group in the middle of the chain. The prepolymers, which were precisely synthesized by RAFT polymerization, were crosslinked with branched crosslinker using activated ester chemistry to produce the network with same molecular weight network chain between crosslinking points. The obtained gel showed UV-induced self-healing owing to the function of the trithiocarbonate groups.

The results of the X-ray diffraction suggest that the d_π-spacing distance for poly(diethylhexyloxy benzo dithiophene-dioctyloxy dithiophene dibenzophenazine (PBDTAFQ) (d_π=3.89Å) was smaller than poly(diethylhexyloxy benzo dithiophene-dioctyloxy dithiophene diphenyl Qu) (PBDTAQ) (d_π=4.36 Å) because of fused-phenyl ring derivative. As a result, PBDTAFQ displayed a higher absorbance at the UV–vis absorption spectra in the film state. And, as a consequence, PBDTAFQ showed an improved short current density (J_SC) in organic photovoltaic cells. The PBDTAFQ:PC₇₀BM blend devices that were fabricated exhibited a power conversion efficiency of 3.4%.

We have formulated the mixing Gibbs energy density for the micelle phase of an amphiphilic block copolymer solution using mean-field lattice theory. By comparing it with the mixing Gibbs energy density for the homogeneous phase, we have observed the transition between the micellization and the liquid–liquid phase separation. The micellization is preferred over the liquid–liquid phase separation at a higher amphiphilicity and a higher degree of polymerization of the block copolymer chain as well as at a higher incompatibility between the two block chains.

Titanium phosphonate (TiOPPh: [Ti₄(μ₃-O)(OⁱPr)₅(μ-OⁱPr)₃(PhPO₃)₃]·thf) was synthesized. TiOPPh was mixed with poly(methyl methacrylate) (PMMA) or poly(vinyl alcohol) (PVA) to prepare organic–inorganic hybrid polymer films. The film using PMMA was formed by the interaction between organic and inorganic components. The temperatures of 10% weight loss of TiOPPh–PMMA were 30 °C higher than that of PMMA only. The film using PVA was formed by the alcohol exchange reaction between TiOPPh and PVA. The transparency of TiOPPh-PVA in the visible region was higher than that of PVA only.

Alkylated dinaphtho[2,3-b:2',3'-d]furan (DNF–V) derivatives are systematically investigated in view of the impact of the substitution position as well as length of alkyl side chains. For both alkylated DNF–VV and DNF–VW derivatives, the solubilities as well as phase-transition temperatures increase as the shorter alkyl chains are attached. Especially, alkylated DNF–VV simultaneously gain the high solubility over 1 wt% and highly stabilized crystal phase up to 199 °C. Furthermore, DNF–V derivatives exhibit deep-blue emission in solid state with the quantum efficiency ranging from 17 to 51%.

In this focused review, we provide an overview of our recent work on the design and synthesis of a new type of side-chain liquid crystal π-conjugated polymeric system associating regioregular poly(3-alkylthiophene) backbones with laterally pending π-conjugated mesogenic groups. Several polymeric architectures have been prepared based on different polymer backbone structures and various side groups, providing important insight into the relationships among the polymeric architecture, nano- and macroscale organization and charge transport properties in such self-organized multi-lamellar macromolecular systems.

Liquid crystals (LCs) have recently gained significant importance in organic photovoltaics (PVs). Power-conversion efficiency up to about 10% has reached in solar cells incorporating LCs. This review presents an overview of the developments in the field of organic PVs with LCs. Comprehensive details of LCs used in bilayer solar cells, bulk heterojunction solar cells and dye-sensitized solar cells have been given. An outlook into the future of this newly emerging, fascinating and exciting field of self-organizing supramolecular LC PV research is provided.

Regioisomeric introduction of barbituric acid and aliphatic tail units onto anthracene core resulted in distinctly different π–π stacking arrangements upon aggregation in nonpolar solvent, resulting in the formation of supramolecular polymers with either non-helical or helically twisted fibrous morphologies. The difference in the topology of these fibrous nanoaggregates is attributed to the conformational difference of anthracene chromophores with respect to the plane of hydrogen-bonded supermacrocycle.

To investigate the effect of the branching position of the alkyl side chain of semiconducting polymers, we synthesized two series of semiconducting polymers based on thienothiophene-2,5-dione (PTTD4Ts) and quinacridone (PQA2Ts). The polymer thin films exhibited small but clear differences in their optical absorption spectra and X-ray diffraction patterns, suggesting that the intermolecular interaction in the solid state varied as a function of the branching position. Although PTTD4Ts did not exhibit a clear correlation between the branching position and charge carrier mobility, the mobility of PQA2Ts gradually increased as the branching position moved away from the backbone.

The influence of the grafting ratio of PMMA on the shape memory effect was studied by synthesizing and characterizing fast recoverable polyurethane/montmorillonite–poly(methyl methacrylate) (PU/MMT–PMMA) composites. PMP₃ with a grafting ratio=3 had the fastest recovery rate, 21.1° per second at 60 °C, whereas the recovery rates of PU and PU/MMT were 6.1 and 9.5° per second, respectively. All the samples recovered to the original shape in 3 s at 80 °C, while PMP₃ displayed a much higher shape memory performance capacity than the other two specimens in 1 s.

The molecular orientation of polymer-stabilized nematic liquid crystals (PSLCs) doped with oligothiophene can be easily manipulated using irradiation with linearly polarized light above a threshold intensity. The photoresponsive behavior depended on the initial molecular orientation, as controlled by the surface treatment of PSLC cells. The threshold light intensity for molecular reorientation was successfully reduced by 30% by optimizing the silane coupler concentration because of the decrease in surface anchoring. Thus, weak surface anchoring leads to a reduced threshold light intensity for molecular reorientation.

A glycopolymer with different mannose incorporation ratios was synthesized via a reversible addition fragmentation chain transfer with acrylamide. The polymers were immobilized onto a gold substrate by the thiol terminate. The glycopolymer layer structures and the glycopolymer–protein interactions were analyzed using a surface plasmon resonance technique. The glycopolymers formed pancake-like structures under dry conditions and were swollen in water. The interaction between the glycopolymer and the protein was enhanced by the cluster effect of the mannose units.

The state-of-the-art atomic force microscopy allows us to observe inner structures of single molecules. Such observation is quite beneficial to study single and self-assembled molecules on surface as well as on-surface chemical reaction. This focus review describes recent technical improvement and achievements in the field of on-surface molecule studied with high-resolution atomic force microscopy.

A carboxylic acid-terminated dendrimer was synthesized via a Steglich esterification of a hyperbranched polyol precursor. Progressive neutralization of the carboxylic groups was carried out, yielding a series of ionic dendrimers. In the ionic clusters, the anion–cation electrostatic interactions induced by the neutralization process dramatically affected the chain mobility of the polymer chains and their order–disorder transition temperatures. The self-assembly of the ionic dendrimers from aqueous milieu into 2D tree morphologies is demonstrated, highlighting their potential use as a highly versatile template for multifunctional semiconductor applications.