Volume 52 Issue 9, September 2020

Macroscopic deformable materials controlled by light have been the subject of growing research interest in the last few decades due to both their fundamental properties and their wide applicability. In this review, examples of photomechanical effects in crystals, polymers, and CLCPs based on photoisomerization and photodimerization are reviewed.

It was found that a synthetic 24-mer β-annulus peptide, which participates in the formation of the dodecahedral internal skeleton of the tomato bushy stunt virus capsid, spontaneously self-assembled into artificial viral capsids with a size of 30–50 nm. The artificial viral capsids could be dressed up with gold nanoparticles, single-stranded DNA, coiled-coil spikes, and proteins by modifying with these molecules at the C-terminus of β-annulus peptides. The artificial viral capsids were notably stabilized by dressing up with human serum albumin and acquired enzymatic activity by dressing up with ribonuclease.

Structural proteins play an important role in shaping the skeletons and structures of cells, tissues, and organisms. This review outlines the definition of structural proteins, methods for characterizing structural proteins as polymeric materials, and potential applications.

In this study, a novel pyrazole–carbodithioate-based chain transfer agent (CTA) featuring an aldehyde group (CTA-CHO) was designed and synthesized. The newly synthesized CTA-CHO was used for the RAFT polymerization of styrene to afford well-defined polystyrenes end-functionalized with an aldehyde unit (PSt-end-CHO). The obtained PSt-end-CHOs feature low Ð values (~1.1), suggesting a living nature of the polymerization. Furthermore, the Passerini three-component reaction was successfully performed on the PSt-end-CHOs.

A stable polymer of urea, polyuret, with nonbonding flat bands, was characterized by means of spectroscopic measurements and theoretical calculations. Polyuret takes a cis-form in the solid state with P2₁/c space group, in which adjacent main chains interact with each other through hydrogen bonds. DFT calculations show the presence of well-defined flat bands that form the highest occupied crystal orbitals, making polyuret a suitable candidate for prospective applications in designing for new types of magnetic materials.

We prepared hybrid porous membranes by the W/O miniemulsion templating method. First, centrifugal accumulation of water nanodroplets and subsequent polymerization of the oil phase were carried out to form porous membranes. The size of the nanodroplets was tuned by the surfactant concentration to control the pore size of the membranes. We could produce pore morphologies such as closed-cellular, open-cellular, and bicontinuous structures by tuning the volume fraction of the nanodroplets. Next, conjugation of gold nanoparticles over the inner pore walls was carried out by utilizing the reducing ability of surfactants.

The linear viscoelastic properties of block copolymer solutions forming hexagonal close-packed cylindrical domains were investigated by using a rheo-optical method. Based on the modified stress-optical rule, the complex shear modulus was separated to four relaxation modes. Considering the sign and magnitude of the stress-optical coefficient associated with each mode, the four modes were assigned to (1) reorientation of corona chains, (2) reorientation of core chains, (3) deformation of domains, and (4) reorientation of grains. The results were compared with those for spherical domains.

Stereocomplex (SC) crystals of polylactide were formed in carbon black-filled Poly(l-lactide) (PLLA)/Poly(d-lactide) (PDLA) composite with 10 and 20 wt% of PDLA during melt blending at the temperature between the melting points of homocrystal and SC crystal. From the analysis of Morisita’s index (I_δ) determined from scanning electron microscopy images and through direct current measurements and alternating current impedance measurements, it was revealed that the increase in the number of SC crystals formed during melt blending improves the filler distribution to achieve a uniform pattern.

To better understand the heat capacities of polymer solids and considering that more than a dozen types of data on the absolute heat-capacity values of polymer compounds already exist, we evaluated the heat capacities of eight polyesters and five poly(oxide)s polymer solids with a carbon and oxygen backbone. Our calculations combined the Tarasov equation, the Einstein equation, and the (C_p − C_V) correction term, accounting for the degrees of freedom of the monomer units. Using the combined Tarasov and Einstein equations, the heat capacities of the analyzed polymer solids were reproduced by only three fitting parameters. The reproduced and experimental heat capacities of all samples except polycaprolactone and poly(3,3-bis(chloromethyl)oxetane) agreed within ±2.5%, and the errors for polycaprolactone and poly(3,3-bis(chloromethyl)oxetane) were within ±4.0%.

This study predicted the absolute values of the heat capacities from the molecular formula per monomer for a main-chain-type polymer below the T_g. The calculations combined the Tarasov equation, the Einstein equation, and the (C_p − C_V) correction term, accounting for the degrees of freedom of the monomer unit. The difference of predicted and experimental heat capacities of poly(4-methyl-1-pentene) was within 8.0% from 90 to 180 K and within ±2.0% agreement from 180 to 300 K. For poly(vinyl benzoate), the values were within ±2.0% from 190 to 350 K, and for poly(1,4-butylene adipate), they were within ±2.0% from 80 to 200 K. The predicted heat capacity was accurate, especially in the high-temperature region above 180 K.

Composites of nylon 6 and large amounts of alumina nanoparticles were prepared to investigate nylon 6 at its interface with alumina. DSC curves obtained by heating and cooling the slowly cooled samples indicate decreases in melting and crystallization temperatures. The melting enthalpy and XRD patterns show a decrease in the degree of crystallization with the addition of alumina. The IR spectra suggest that hydrogen bonds were enhanced at the interface.

(2 × 4)-Type tetra-PEG ion gels were prepared through a copper-free azide–alkyne cycloaddition reaction between tetra-branched poly(ethylene glycol) and linear tetra(ethylene glycol). The tensile tests showed that the reaction efficiency of the cross-linking was over 90%. The prepared ion gels exhibited high mechanical toughness and stretchability characteristic of tetra-PEG gels. The electrochemical window of the ion gels was the same as that of the ionic liquid inside the gel. The ionic conductivity of the ion gel (30 wt% polymer concentrations) was 8.9 × 10⁻⁴ S cm⁻¹ (25 °C, anhydrous conditions).

The thermoresponsiveness of hydrogel microspheres (microgels) was visualized in situ at the nanoscale using temperature-controllable high-speed atomic force microscopy (TC-HS-AFM). The morphological changes of the microgels are strongly affected by their packing conditions and by their adsorption on a solid substrate. The isolated microgels attached to the substrate show a simple increase in height and a constant width with decreasing temperature. On the other hand, both the width and the height of the densely packed microgels increase, and the structures of the microgels change from spherical to hexagonal during cooling.

Microtubules (MTs) consisting of tubulins are important targets of drugs for MT-related diseases. We have previously designed a linear Tau-derived peptide (TP) that binds to the interior of MTs. In this article, a cyclic TP (TCP) was developed for enhanced binding to tubulin and stabilization of MTs. The fluorescently labeled TCP exhibited a remarkably enhanced binding affinity to tubulin compared to the linear TP. The stabilization of MTs by binding of TCP was demonstrated, such as formation of typically unstable MTs in the presence of guanosine triphosphate.

We examined the differences between the resulting polymer structures in the cases of a coating and an adhesive employing the same formulation. The UV-curable coating yielded polymers terminated by either a hydroxyl group or a terminal carbonyl group as the main products, suggesting that bimolecular termination was strongly inhibited by oxygen. On the other hand, the UV-curable adhesive yielded a multitude of disproportionation products, whereas some polymers underwent hydrogen abstraction from the polymer backbone, resulting in β-scission of the midchain radical to generate polymers with an α-substituted acryloyl group.

A nitrile N-oxide-functionalized polypeptide was synthesized by a two-step method involving the combination of ring-opening polymerization of an amino acid N-carboxyanhydride (NCA) monomer using a primary amine initiator containing a nitroalkane group and a subsequent terminal conversion. The formed peptide was fully characterized by NMR, FT-IR, and MALDI-TOF MS measurements. The catalyst-free grafting reaction of the formed functionalized peptide with rubbers containing double bonds was achieved with high efficiency via an environmentally benign process. These results surely contributed to the development of novel peptide-grafted polymers.