Volume 53 Issue 2, February 2021

The chain-growth polymerization mechanism is essentially unsuitable for sequence control due to its statistical propagation feature. However, the development of reversible-deactivation radical polymerization has opened the door to the sequence control. Our group has developed some methodologies and concepts for the synthesis of sequence-controlled oligomers/polymers via radical polymerization: it is crucial to introduce some additional components into the initiator and/or the monomer for reversible-deactivation radical polymerization and in most cases these components are designed to be removed or transformable afterward.

Our recent studies on the zincate complex dilithium tetra-tert-butylzincate-catalyzed transesterification and polymerization are reviewed. In the first part of this report, the ROP of ε-caprolactone catalyzed by TBZL is described. In the second part of this report, the acylation and transesterification of alcohols with vinyl acetate and carboxylic esters catalyzed by TBZL are summarized. Next, TBZL-catalyzed polycondensations of diphenyl carbonate (DPC) with diols are discussed. In the last part of this report, the transesterifications of poly(phenyl methacrylate) (PPhMA) side chains with alcohols catalyzed by TBZL are described.

This focus review describes the synthetic routes to cyclic compounds and cyclic polymers via spontaneously occurring cyclization processes using (1) rotaxane chemistry and (2) dynamic covalent chemistry. Systems with rotaxane-based structures proceed via the spontaneous and selective cyclization of two self-complementary molecules and a macromolecular rotaxane switch, which results in a topology change from linear to cyclic. Systems based on dynamic covalent chemistry use exchange reactions of bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS) units. Controlling the dynamic nature of BiTEMPS-based molecules provides cyclic topologies via spontaneously and selectively occurring cyclization processes.

We reviewed our recent studies on optical manipulation techniques for microspectroscopic analysis of optically trapped polymers. A focused laser beam exerts an optical force on polymer chains, leading to the microassembly formation of them. We applied the conventional optical tweezers for the concentration determination techniques of phase-separated thermoresponsive polymer chains by combining with microspectroscopies. To overcome the limitations of the conventional optical tweezers, localized surface plasmon has attracted much attention. Finally, we introduced our original manipulation technique based on nanostructured semiconductor-assisted optical tweezers; NASSCA optical tweezers.

Our recent studies on how nanostructures can be self-assembled in discotic liquid crystals to create self-organizing functional systems of discotics with tuned physical properties are reviewed. In the first part of the article, charge carrier and semiconducting properties of discotic liquid crystals in the form of 1-D molecular wires are described. The second part of this report summarized our recent results on self-assembly of Ag, Au, Cu, and graphene nanoparticles, carbon dots, CdTe and CdSe quantum dots, gold nanorods, CdS nanoribbons, silver nanodisks, and graphene sheets in discotics.

Recent studies on exploration of mechanical deformation of microtubules under tensile and compressive stress, using a newly developed methodology, have been reviewed. In the first part of this review article, development of the methodology and its utility in studying the mechanoresponsiveness of microtubules have been described. In the second part, applications of the recently developed methodology in studying dynamic soft interfaces have been elaborately discussed.

RAFT aqueous emulsion polymerization of vinyl acetate (VAc) was performed using poly[di(ethylene glycol) vinyl ether] (PDEGV) macromolecular chain transfer agents. The emulsion polymerization directly induced PDEGV-b-PVAc diblock copolymer assemblies in water. Owing to the characteristic PDEGV as a highly hydrophilic steric stabilizer, this facile formulation enables the production of various particle morphologies, such as spheres, rods (ellipsoids), and vesicles, depending on the composition of the block copolymer. Each morphology change in the nanoparticles via RAFT aqueous emulsion polymerization owes its success to the recent RAFT polymerizations of vinyl ethers.

Carboxylated butyl rubber derivatives were obtained by reacting the isoprene units in the isobutylene copolymer with alkylmercaptanoic acids comprising alkyl spacers of different lengths. The yield of the reactions varied from 80 to 90% for direct reaction of the copolymer containing 1,4-isoprene units, but increased to 90–98% if the 1,4-units were isomerized to terminal alkenes prior to the reactions.

The structural evolution of β-iPP with two different supermolecular structures during the simultaneous biaxial stretching process was studied. The two samples showed different structural evolution modes. β-hedrites exhibited violent cavitation behavior during the initial stage of deformation, but in the late stages of stretching β-hedrites formed numerous dense regions, which hindered microvoid formation and led to a poor pore size distribution. Conversely, β-spherulite generated abundant microfibrillar structures, and abundant microvoids were formed, forming a membrane with a superior pore size distribution.

Latex films typically suffer from poor mechanical strength compared to solution-cast latex films. In the present study, to obtain tougher latex films, we investigated the relationship between the mechanical properties and the nanostructures of films prepared at different film-formation temperatures (FFTs), i.e., FFTs above and below the glass-transition temperatures (T_g) of the microspheres. Tensile tests revealed that the films showed the highest fracture energies when the film was formed at a temperature higher than the T_g of the microspheres and followed by annealing.

Self-healable and cell-compatible polyurethane elastomers cross-linked by charge-transfer complexes between electron-rich pyrene (Py) and electron-deficient naphthalene diimide (NDI) were fabricated by simply blending two linear polymers with Py or NDI as a repeating unit. The elastomers with different blend ratios self-healed damage over 1 day in mild conditions, including in air and water at 30–100 °C. The good cell compatibility of the polyurethane elastomers was demonstrated by culturing two kinds of cells on the thin film substrates.

A surface-controlled cooperatively rearranging region (SCC) model mimics the segmental dynamics of supercooled liquids. By introducing surface/interface effects into the SCC model, the size-dependent dynamics of nanosized polymer materials with various geometries were predicted. The calculated glass transition temperature (T_g) and fragility for filled spheres of polystyrene coincided qualitatively with experimental observations. The results also showed that T_g(filled sphere) > T_g(filled fiber) > T_g(free-standing film) when compared at the same surface area to volume ratio, whereas for fragility, the opposite trend was found.

The fabricated polymeric liquid crystal beads surfaces consist of aligned rhodamine B-derived active sites possess capacity of sensing copper ions in tested solutions. The color of the beads changed to deep pink while copper ions exist in the solutions, whereas it can be easily recycled by adding aqueous ammonia, indicating the beads applied as a powerful monitoring tool.

We chose an autoinduction (IPTG-independent) system for overexpression of recombinant proteins using E. coli as the expression host. In autoinduction, glucose and lactose are used as main carbon sources for cell growth. When the glucose is almost completely consumed as the first growth of E. coli., the carbon source turns to lactose, accompanied by regioselective chemical transformation of lactose to allolactose, which acts as the trigger for activation of transcription by releasing the repressor. Using this system, we achieved marked overexpression of the biosynthesized GFP and aECM-CS5-ELF.

A hyperbranched polymer (HBP) additive is used to explore short-range molecular motions in the glassy state of crosslinked epoxy amine networks via subambient β relaxations as measured by dynamic mechanical thermal analysis. Increasing HBP addition increased modulus and stress, while reducing yield strain. Pre-reaction using an isocyanate linkage between the HBP and network comparatively reduced modulus while increasing stress and strain. Glassy state mobility of the epoxy amine network as a result of HBP addition, could be directly related to many changes in mechanical properties observed.

A series of ester-functionalized polythiophenes (P3OETs) with precisely controlled head-to-tail (HT) ratios was synthesized via palladium-catalyzed direct arylation polycondensation (DArP). The ionization potentials and optical bandgaps of P3OETs decreased as their HT ratios increased because of the increased backbone coplanarity and extensive π-electron delocalization. The method of precisely controlling the regioregularity and HT ratio can contribute to the design of new polythiophene derivatives with enhanced electronic functionality.

Poly(γ-glutamic acid) (PGA) is a biopolymer produced by Bacillus spp. via the γ-amide linkages of d- and/or l-glutamate. PgsB, PgsC, and PgsA are the minimum protein set required for PGA production in B. subtilis, and PgsE improves PGA productivity. Analysis by size-exclusion chromatography combined with multiangle laser light scattering revealed that the molecular weight of PGA was M_w = 2,900,000 g mol⁻¹ or predominantly M_w = 47,000 g mol⁻¹ in preparations derived from B. subtilis cells with or without pgsE, respectively. PgsE may be required to increase the apparent molecular weight of PGA.