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This focused review provides an overview of our recent work and related research regarding the precise anionic ring-opening polymerization (AROP) of substituted epoxides, including alkylene oxides, glycidyl ethers, and glycidyl amines, using t-Bu-P4 as the phosphazene base catalyst to produce functional polyethers, such as homopolymers, block copolymers (BCPs), and topologically unique polymers. First, the fundamental aspects and applicable monomer scope of the t-Bu-P4-catalyzed AROP are discussed. Subsequently, the applications of the AROP system for synthesizing functional materials and architectural polymers are presented.
Despite the tremendous efforts made in recent decades to remove imperfections from gels, discernible signs of spatial defects have been persistently observed in gels. Researchers believe that gels are inherently heterogeneous. In this focus review, I briefly introduce a recent finding from our research group’s efforts to fabricate polymer gels free of spatial heterogeneities via “bond percolation”. The commonly observed scattering profiles for the spatial defects disappeared in the homogeneous gels. The newly observed scattering profiles are a benchmark for gel structures.
The functionalization methods of polymeric materials using various types of cross-links, such as supramolecular cross-links, photo cross-links, and associative dynamic covalent bonded cross-links, were described. First, the enhancement and precise tuning of the thermal and mechanical properties are demonstrated in the supramolecular cross-link-based and photo cross-link-based designs. In the latter section, the design and physical property tuning of functional materials based on a special type of cross-linked materials with associative dynamic covalent bonded cross-links, known as vitrimers, are demonstrated.
Our recent development on healable soft materials that utilize block copolymer self-assembly in ionic liquids is reviewed. We begin by discussing photohealable ion gels that respond to specific wavelength of light irradiation by forming and collapsing stimuli-responsive networks. Then, we highlight on the self-healing ion gels based on synergetic combination of supramolecular interaction and block copolymer self-assembly, which realize high mechanical strength and fast self-healing ability in the absence of any external stimuli.
Polymeric hydrogen carrier with high thermal stability was prepared by incorporating isopropanol and acetone units into polymers via a facile reaction process. Reversible hydrogen fixing and releasing were achieved with full conversion under mild conditions. Temperature-dependent facile hydrogenation and dehydrogenation cycle that operated at temperatures higher than the boiling points of isopropanol and acetone, in the presence of an iridium complex catalyst, was established by virtue of having these groups as pendants of the vinyl chain, with a compact repeating unit to maximize the mass hydrogen storage density of 2.8 wt%.
Amphiphilic diblock copolymers (M98En) composed of hydrophilic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and hydrophobic poly(2-methoxyethyl acrylate) were synthesized via controlled radical polymerization. M98En formed micelles in water, which can encapsulate hydrophobic guest molecules into the core. The micelles did not interact with proteins in an aqueous solution due to the PMPC shells.
We developed a W/O miniemulsion reactor system enabling the preparation of biopolymer nanoparticles and control of their morphologies and inner microstructures. We produced agarose hydrogel nanoparticles (AgarH) by the gelation of agarose in nanodroplets of a W/O miniemulsion. Next, we prepared agarose xerogel nanoparticles (AgarX) by precisely tuning the water evaporation from AgarH. We controlled the morphologies (solid and hollow) and crystal structure of AgarX by changing the pressure and temperature. The resultant AgarX possessed high crystallinity and thereby exhibited water resistance better than AgarH.
Poly(trimethylene carbonate) (PTMC) based polymers were blended with N,N,N-trimethylchitosan (TM-CS). The tensile strength of the chitosan (CS) and TM-CS films blended with PTMC was found to cause brittleness, but a PTMC derivative copolymer bearing carboxylic acid improved the elongation properties of TM-CS. A softer film was obtained for a blend film composed of TM-CS with 25% consisting of an added PTMC derivative copolymer bearing a 10% carboxylic acid moiety on the side chain. This is the first report of the modification of CS using polymers with a PTMC backbone.
A preparation of polyacrylate-based vitrimer-like elastomers with dynamic bond-exchangeable cross-links is demonstrated. The component polymer is a poly(ethyl acrylate)-based copolymer bearing pyridine groups randomly, which was cross-linked by a quaternization reaction of pyridine groups with dibromo cross-linkers (dibromo hexane). The bond exchange is induced via trans-N-alkylation of quaternized pyridines at high temperatures, which is revealed by temperature-ramp FT-IR, elongational creep, and stress-relaxation tests. Some useful functions of the present material, such as reprocessability, thermal and chemical recyclability, are provided due to the bond exchange nature.
In this Note, the heat-proofing and anti-plasticizing nature of poly(ethylene carbonate) by the addition of a defibered plant (DP) is presented. The DP was obtained via simple wet-milling treatment for water-dispersed Japanese cedar. The presented results encourage us to use plants as functional fillers without a special chemical/biological reaction.
