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Photoswitchable and interconvertible cationic/radical copolymerization was investigated by combining a Lewis acid-catalyzed cationic polymerization with a photoinduced electron/energy transfer (PET)-reversible addition-fragmentation transfer (RAFT) polymerization, in which the dormant terminal group of the RAFT polymerization was employed as the dual mediator for cationic and photoradical polymerizations. Zinc porphyrin complex (ZnTPP) as the photoredox catalyst and bulky boron-based Lewis acid, B(C6F5)3, was successfully combined to induce the concurrent and interconvertible cationic/radical copolymerization of vinyl ether and methyl acrylate under visible light irradiation.
A new thermally latent cocatalyst, based on 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), has been specifically designed for “on-demand” synthesis of polyurethanes in the presence of DBTL as catalyst. This nitrophenyl-based isocyanurate cocatalyst exhibited a low cleavage temperature keeping the system almost inactive at 20 °C and allowing fast polymerization only after increasing temperature up to 60 °C by the release of active DBN.
Mechanical properties of rubber nanocomposites are believed to closely related to the chain dynamics at the interface with fillers. We here tackle this hypothesis combining traditional rheological measurements with our published results obtained by a modern technique of interfacial sensitive spectroscopy.
The equilibrium melting temperature (\(T_{\mathrm{m}}^0\)) of natural rubber crystals was reexamined by the Hoffman–Weeks plot and the Gibbs–Thomson plot using the lamellar thickness obtained from the same sample as the one used for the measurement of melting temperature. The sample was prepared from deproteinized latex. As a result, the \(T_{\mathrm{m}}^0\) of NR was estimated to be 61 °C. At the same time, the fold-surface free energy was estimated to be 0.046 Jm−2. These values should be more reliable than the previously assumed values.
The block glycopolymers with specific arrangement of sugar ligand and electric charges were synthesized via RAFT living radical polymerization, where the block polymers were efficiently obtained using two orthogonal reactions of Huisgen and thiol-epoxy ring opening reactions. The molecular recognition abilities of the block glycopolymers was examined.
Pd-initiated polymerization of diazoacetates containing oligo(ethylene glycol)-substituted cyclotriphosphazenes was conducted to yield carbon-carbon main chain polymers bearing an oligo(ethylene glycol)-substituted cyclotriphosphazene on every main chain carbon atom. The resulting organic–inorganic poly(substituted methylene)s were found to show an LCST-type phase separation in aqueous media, and thus their thermosensitive behavior was evaluated by turbidity measurements.
Controlled cationic cyclopolymerizations of divinyl ethers with cyclohexene, norbornene, norbornane, cyclic acetal, or adamantane moiety were carried out. High-molecular-weight star-shaped cyclopolymers were synthesized by the reaction of the formed living cyclopolymers with a small amount of divinyl ether crosslinking agent. Glass transition temperatures (Tg’s) of both the cyclopolymers and star-shaped cyclopolymers were as high as 145−229 oC. Methacrylate-terminated end-functionalized star-shaped cyclopolymers were synthesized by the functionalized initiator-based living cationic cyclopolymerization of divinyl ethers followed by the chain linking reactions among the formed living cyclopolymers with divinyl ether crosslinker. The obtained end-functionalized star-shaped cyclopolymers were subjected to thermal crosslinking reaction to give star-shaped cyclopolymer networks with film-forming ability.
We synthesized poly(bisphenol A-co-ephichlorohydrin)–titanium phosphonate clusters (Ti4P3: [Ti4(μ3-O)(OiPr)5(μ-OiPr)3(O3PPh)3]·thf; Ti4P4: [Ti(OiPr)(acac)(O3PPh)]4; Ti7P6: Ti7(μ3-O)2 (OiPr)6(μ-OiPr)6(O3PBnBr)6). From the result of swelling test using tetrahydrofuran, Ti7P6 cluster showed highest cross-linking efficiency.
Polypeptides containing periodic aromatic residues, 4-aminobenzoic acid (Abz), in their main chains were synthesized via papain-catalyzed chemoenzymatic polymerization of tripeptide ester monomers under moderate conditions in aqueous buffers. The secondary structures of the Abz-containing polypeptides were investigated by IR and wide-angle X-ray diffraction analysis. The WAXD profile of poly(GlyAbzGly) was similar to that of polyGly, whereas poly(AlaAbzAla) adopted a sheet-like structure similar to the β-sheet of polyAla.
We synthesized cellulose nanofiber (CNF) modified with 9,9′-bis(aryl)fluorene, possessing cardo moieties (BCNF), and evaluated the properties of its polyamide 6/66 (PA) composites. As a result, it was revealed that BCNF was well dispersed in PA and had a strong reinforcing effect—even in a temperature range above the glass transition temperature—compared with unmodified CNF. This is attributed to the improvement of the interface affinity between BCNF and PA derived from the bulky and hydrophobic structure of BPFG.
Bridged polysilsesquioxane membranes have been expected as robust RO membranes for water desalination. However, water permeability of the membranes was not sufficiently high. In the present work, we studied interfacial copolymerization of bis[(triethoxysilyl)propyl]amine (BTESPA) and bis(triethoxysilyl)ethane (BTESE), which resulted in ~10 times higher water permeance of the membrane than that of the BTESPA homopolymer membrane with keeping NaCl rejection at nearly the same level. It was also found that the copolymerization with BTESE improved the thermal stability and chlorine resistance of the membranes.
A triple-helical peptide, H-(Pro-Pro-Gly)10-OH (PPG10) forms complex with NaHeparin in aqueous NaCl at ionic strengths of 20 and 50 mM and at 15 °C. The triple helix of PPG10 in the resulting complex is appreciably stabilized and the melting temperature of the triple helix is considerably higher than without NaHeparin. Analyses of the scattering function of the complex indicate that the molecular shape is substantially different from that of the previously investigated complex, suggesting specific attractive interactions between PPG10 and NaHeparin.
Bulk copolymerization of bis(acryloylhydrazine) with N,N-dimethylacrylamide or N,N-diethylacrylamide yielded a transparent cross-linked polymer monolith. Upon treatment with a sodium hypochlorite solution, the cross-linked monolith dissolved in water by de-crosslinking via oxidative degradation of the diacylhydrazine moiety.
The nucleating effect of silk fibroin nanodisc on the crystallization behavior of poly(l-lactic acid) (PLLA) was investigated by polarizing optical microscope observations and the differential scanning calorimetry measurements. The experimental results show that the small amount of SFN (only 1%) reduces the induction period and the crystallization half-time while it increases the final degree of crystallinity. It was found that the SFN works as a nucleation agent by increasing the number of nuclei about four times while it does not change the growth rate of spherulites.
Soybean protein isolate (SPI) was bonded to carboxymethyl cellulose (CMC) by a hydrazine bond to prepare SPI-CMC carriers for pesticide applications. AVM/SPI-CMC was obtained by encapsulating avermectin (AVM) with SPI-CMC through thermal denaturation. SPI-CMC could improve the anti-UV performance of AVM and slow down the decomposition rate of AVM. The hydrazone bond and carboxyl groups showed pH responsiveness, which could release drugs rapidly in an acidic environment. Environmentally friendly SPI-CMC could protect and release pesticides continuously, which could improve the efficiency of pesticides.
Radical copolymerization of N-substituted maleimides and olefins provides AAB sequence-controlled copolymers by penultimate unit control. In this study, we investigated the steric, resonance, and polar effects of N-substituents on sequence control during copolymerization of various N-substituted maleimides with diisobutene and limonene in chloroform at 60 °C, and concluded that less bulky and more electron-donating substituents effectively induced the penultimate unit effect. We also demonstrated that 2:1 sequence-controlled maleimide copolymers was efficiently produced during radical copolymerization of limonene and N-phenylmaleimides with an electron-donating substituent.
We carried out the conventional radical polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization of di(1-adamantyl) fumarate, bis(3,5-dimethyl-1-adamantyl) fumarate, 1-adamantyl isopropyl fumarate, and 3,5-dimethyl-1-adamantyl isopropyl fumarate. Triblock copolymers consisting of rigid and flexible segments were synthesized by the RAFT polymerization of 2-ethylhexyl acrylate using poly(dialkyl fumarate)s as the macro-chain transfer agents. The excellent thermal stability of the adamantane-containing poly(dialkyl fumarate)s was confirmed by thermogravimetric analysis. The alignment of the rigid poly(dialkyl fumarate)s chains in the solid-state was revealed by X-ray diffraction.
We developed biobased nanocapsules with enzymatic degradability, which were generated by the layer-by-layer deposition of enzymes and polypeptide over a liposome. Our developed nanocapsules exhibited layer-specific degradation by enzymes, which enables the release of cargo through degradation of the capsule wall as well as accumulation and targeting of nanocapsules through the emergence of surface properties and functionalities such as bone-targeting ability and cell-penetrating ability by unveiling an inner polymer layer.
