Invited Review

Based on the systematic classification and on the isomeric properties of polymer chain topologies, a variety of novel multicyclic macromolecular constructions has now been rationally designed and subsequently realized. In particular, an electrostatic self-assembly and covalent fixation process, optionally in conjunction with effective covalent linking chemistry, has been demonstrated as a new synthetic protocol for unprecedented polymers possessing multicyclic topologies.

The new ‘Sea/Island’ composite-spinning technology has solved the problem of unstable quality associated with conventional mass-production nanofibers. ‘Sea/island’ composite spinning achieves the high-strength polyester nanofiber based on conjugated (two components) spinning theory. The separation process between sea–islands components is successful with 1000 times faster in alkali solution resolution sea polymer than island polymer. Nanofiber has a very large surface area, absorption, distribution and filtration effect, which are suitable for a variety of applications, including functional sportswear, inner wear, skin-care products, filters, precision grinding cloth, and so on.

A retardation film consists of optical polymer to control polarized light by the oriented birefringence. One of the issues of the films is wide-banding of birefringence. We have researched a novel molecular design to control dispersion, and found that the wide-band properties appear in a narrow range near the birefringence zero point, which is determined by the volume fractions of the positive monomer units to the negative units. The wide-band retardation film has been industrialized using a novel co-PC with a fluorene ring based on the molecular design.

Pd complexes with diimine ligands promote controlled cyclopolymerization of 1,6-dienes and 1,6,11-trienes to afford the polymers containing 1,2-trans-cyclopentane groups with well-regulated stereochemistry. Copolymerization of the dienes with ethylene and α-olefins also proceeds to give functionalized polyolefins. The polymerization of the monomers with oligomethylene spacer yields the polymers with five-membered rings in accurate density and distribution along the polymer chain. 4-Alkylcyclopentenes and alkenylcyclohexanes also get polymerized by the Pd complex to afford polymers with 1,3-trans-cyclopentane groups and 1,4-trans-cyclohexane groups, respectively. Isotactic polymer of 4-alkylcyclopentenes show liquid crystalline properties.

Glycopolymers with pendant saccharides are biofunctional polymers that interact with saccharide recognition proteins. The glycopolymers show the strong molecular recognition ability owing to the multivalency. These polymers were prepared by the polymerization with sugar derivatives or by the saccharide addition to the polymer backbone. The glycopolymers can be applied for cell cultivation, drug delivery, and biosensing. The living radical polymerization provided the precise structure of glycopolymer, which was useful for analysis of the protein–saccharide interactions. The living radical polymerization also provided the hybrid biomaterials that can be used for biosensing and biomaterials.

Recent developments in artificial cutters for site-selective scission of single-stranded DNA are described. With the cutters composed of two oligonucleotide additives and Ce(IV)/EDTA, long single-stranded DNA can be selectively cut at target site and manipulated according to our needs.

Antifreeze proteins (AFPs) function as inhibitors of ice growth. Computer simulation studies have contributed to the understanding of the molecular-scale mechanism of ice growth inhibition by AFPs. For example, molecular dynamics simulations of a growing ice–water interface to which a winter flounder AFP for a {20\(\overline{2}\)1} pyramidal plane is bound have indicated that the growth rate of ice surrounding the AFP decreases drastically, owing to depression of the ice melting point through the Gibbs–Thomson effect.

Recent work is reviewed in which nanoporous polyethylene, derived from a polymeric bicontinuous microemulsion, is used as a nanocasting template in the synthesis of a catalogue of porous materials, including ceramics, thermosets, conducting polymers, and hierarchical inorganic and organic materials. Their structures replicate that of the bicontinuous microemulsion precursor with high fidelity, resulting in disordered and three-dimensionally continuous arrangements of multiple phases having a characteristic length scale of ∼100 nm.

We demonstrated that a method based on the analysis of both orientational birefringence and photoelastic birefringence is effective for designing polymers that are processed in a molten state and used in a glassy state. The designed polymer exhibits no birefringence for any orientation of the polymer main chains or under elastic deformation. Birefringence is close to zero even in injection-molded plates of the polymer. We have also shown that it is possible to compensate and control the birefringence of polymers using inorganic nanocrystals, and we have obtained valuable information on the optimal size of nanocrystals for compensation and control of birefringence.

Polyolefins (polypropylene (PP), polyethylene and so on) and polyolefin rubbers (ethylene propylene diene monomer, ethylene propylene elastomer and so on) are the most widely used polymers. Therefore, a development of a polyolefin and polyolefin rubber–clay nanocomposite has been desired for a long time. As these polyolefin polymers do not include any polar groups in its backbone, it was thought that the homogeneous dispersion of the silicate layers would not be realized. But we have successfully developed these polymer–clay nanocomposites by using various methods.

The footprints of a macromolecular synthetic chemist were left on the sands of time. Novel anionic addition polymerization of fluorinated vinyl monomers, which generally show poor homopolymerization reactivity, has been developed. Anionic polyaddition has been achieved by the double Michael addition of bis(2-trifluoromethylacrylate)s to active methylene compounds. Radical addition of fluorinated vinyl monomers with many organic compounds possessing carbon–hydrogen bonds has been accomplished and amplified to the polyaddition reaction to incorporate fluorinated vinyl monomers into polymer main chains. The facile carbon–carbon bond formation reactions have been accomplished by the aid of fluorine substituents.

This article reviews the living homopolymerization and copolymerization of propene, 1-alkene and norbornene with ansa-dimethysilylene(fluorenyl) (amido)dimethyltitanium and its derivatives, 1–4, correlating with the effects of cocatalysts, solvents and the substituent of the fluorenyl ligand on the catalytic features, such as livingness, propagation rate, syndiospecificity and copolymerization ability. The synthesis of novel olefin block copolymers and their catalytic synthesis are also introduced by the use of the living system.

The movement toward a recycling-based society through the essential development of recyclable materials alongside technologies for controlling recycling, for example, upgrade recycling of commodity plastics, selective transformation of engineering plastics, selective depolymerization of various polymers in supercritical fluids, crosslinking-decrosslinking control using reversible reactions and developments in biomass-based recyclable polymers is reviewed.

New types of polymer hydrogels (nanocomposite gels, NC gels) and soft polymer nanocomposites (M-NCs) with novel organic/inorganic network structures were synthesized using disk-like inorganic clay nanoparticles as multifunctional crosslinkers to form new network systems. Both NC gels and M-NCs have extraordinary optical and mechanical properties, such as ultrahigh reversible extensibility, as well as a number of new characteristics relating to polymer/clay morphology, stimulus-sensitivity, biocompatibility, surface properties, micropatterning and so on. The serious disadvantages (intractability, mechanical fragility, optical turbidity, poor processing ability, low stimulus sensitivity) associated with the conventional, chemically crosslinked polymeric materials were overcome in NC gels and M-NCs.

Three super-tough gels and their deformation mechanism as revealed by small-angle neutron scattering

Precise synthesis of dendrimer-like star-branched polymers, a novel class of structurally well-defined hyperbranched polymers, by stepwise iterative methodologies based on the ‘arm-first’ divergent approach is described. The methodologies basically involve a linking reaction of chain-functionalized living anionic polymer(s) and a transformation reaction to regenerate the next reaction sites. By repeating the two reaction steps, high-generation and high-molecular-weight dendrimer-like star-branched polymers and their block copolymers were successfully synthesized. The resulting polymers were characterized by small-angle X-ray scattering, viscosity and atomic force microscopy measurements to estimate their sizes, shapes and solution behavior.

The metal-catalyzed living radical polymerization has now been developed diversely in terms of the catalytic systems, controllable monomers, well-defined polymer structures and combinations with stereospecific radical polymerization. This review describes a short overview of recent developments in metal-catalyzed living radical polymerization mainly focusing on our recent research studies related to the subject.

This article reviews the development of catalysts for ring-opening metathesis polymerization (ROMP), synthesis of polymers bearing amino acids and peptides by ROMP of functionalized norbornenes, formation of aggregates and micelles, and applications of the polymers to medical materials. It also describes the control of monomer unit sequences, that is, living polymerization to synthesize block copolymers, and alternating copolymerization that is achieved on the basis of acid–base interactions.

Hyperbranched poly(ether sulfone)s (HBPES) possessing sulfonic acid at the terminal point were prepared by the electrophilic reaction of sulfonium ions to electron-rich benzene rings starting two kinds of AB₂ monomers. First, linear and hyperbranched multiblock copolymers were successfully prepared by the reaction of oligomeric linear PES and AB₂ monomer. Next, from these multiblock copolymers, a linear and hyperbranched PES blend was prepared and applied as ion-exchange membranes for fuel cells. The blend films showed comparable ion-exchange capacity with Nafion 117 membrane.