Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41428-023-00822-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

The ring-opening metathesis polymerization (ROMP) of cyclic olefins with niobium(V) pentaalkoxide catalysts was studied. In the presence of zinc, benzylidene dichloride, and chlorotrimethylsilane, in situ niobium species was formed and ROMP reaction proceeded. Among niobium pentaalkoxide group, Nb(OEt)5 achieved the smallest dispersity value of the polymer and provided trans selective polynorbornene. In this paper, we discussed the role of additives and expected how the polymer was synthesized with Nb(OEt)5/TMSCl/Zn/PhCHCl2 system. We also elucidated the intermediate using some measurement.

DOI： 10.1016/j.mcat.2023.113393

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DOI： 10.1038/s41428-023-00770-z

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DOI： 10.1002/pol.20220765

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Language：English   Publishing type：Research paper (scientific journal)  

Trisubstituted 1,3,5-tri(benzimidazolyl)benzene derivatives were synthesized from ʟ-alanine, ʟ-valine, ᴅ-valine and glycine, and their self-assembling behavior and stimuli-response in solution and gel states were evaluated. Circular dichroism/UV-vis absorption spectroscopic and dynamic light scattering measurements revealed that the compounds formed H-aggregates via intramolecular hydrogen bonding and π-π stacking interactions in nonpolar solvents such as CHCl3, whereas collapse of the aggregates was confirmed by MeOH addition. Quantum mechanical calculations and molecular dynamics simulations also supported aggregation in CHCl3. Rheological analysis and morphology observation revealed the formation of a fibril like structure by further assembling of aggregates at a high concentration in CHCl3.

DOI： 10.1002/chem.202203703

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The polycondensation of N-((3,5-diamino)benzoyl)-ʟ-alanine dodecyl ester (1L) with p-phthalaldehyde (2) was carried out to obtain poly(1L-2), a novel optically active polymer containing Schiff base moieties in the main chain. A series of analogous polymers with Schiff base moieties were also synthesized from N-((3,5-diamino)benzoyl)-ᴅ-alanine dodecyl ester (1D) and N-((3,5-diamino)benzoyl)glycine dodecyl ester (1G) with various feed ratios. The polymers exhibited CD signals assignable to exciton coupling-based chirality in CHCl3 depending on the feed molar ratios of 1L/1D and 1L/1G. Poly(1L-2) exhibited lyotropic liquid crystallinity in CHCl3 and THF.

DOI： 10.1016/j.polymer.2023.125703

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Language：English   Publishing type：Research paper (scientific journal)  

Platinum-containing macrocycles (platinacycles) have gained attention due to their unique photoelectric properties. In the present study, a novel conjugated platinacycle was synthesized by the dehydrochlorination coupling reaction of a bipyridine dichloroplatinum(II) complex and a 3,6-diethynylcarbazol derivative. The structure of the platinacycle was confirmed by 1H/13C, 1H-1H COSY, HMQC, HMBC, DEPT NMR spectroscopies in conjunction with DFT calculations, IR spectroscopy and MALDI-TOF mass spectrometry. The platinacycle exhibited a UV-vis absorption around 540 nm assignable to ligand-ligand charge transfer, and birefringence in DMF, possibly due to alignment of molecules.

DOI： 10.1039/d2dt03524c

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Publishing type：Research paper (scientific journal)  

This study deals with chirality induction to the main chain of platinum (Pt)-containing aryleneethynylene polymers by ligand exchange reactions. The optically inactive polymers containing –(–C[tbnd]C–trans-Pt(PPh3)2–C[tbnd]C–)– moieties in the main chain undergo ligand exchange reactions with P-chiral diphosphines, (R,R)-BenzP* and (R,R)-QuinoxP* to give optically active polymers containing –(–C[tbnd]C–cis-Pt(P-chiral diphosphine)–C[tbnd]C–)– moieties. The ligand-exchanged polymers exhibit CD signals based on the conjugated main chain, indicating chirality induction to the main chain by the P-chiral ligands. The QuinoxP*-ligated polymers emit photoluminescence likely based on the transition from the QuinoxP* moieties. Quantum mechanical calculations predict reasonable CD, UV–vis absorption and photoluminescence spectra.

DOI： 10.1016/j.polymer.2022.125576

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

The functionalization of the chain end of a polymer is gathering increasing attention in the field of synthetic polymer chemistry. The present study is the first example to demonstrate the incorporation of a platinum-acetylide complex at the terminal of a polynorbornene derivative. N-Benzyl-5-norbornene-2-exo,3-exo-dicarboxyimide (1) was polymerized with Grubbs 3rd-generation catalyst (G3). The polymerization was quenched with (Z)-1,4-bis(3-((trimethylsilyl)ethynyl)phenoxy)-2-butene (2) to obtain poly(1)′, followed by the cleavage of trimethylsilyl group and dehydroiodination coupling with trans-bis(tributylphosphine)phenylethynyl iodo platinum (3a) to obtain poly(1a), which was functionalized with a platinum complex at the chain end. Poly(1)′ exhibited no remarkable absorption around 330 nm, while poly(1a) exhibited an intense absorption based on ligand-to-metal charge-transfer transition. Poly(1b) functionalized with a naphthylamide ethynyl platinum complex was synthesized in a similar fashion. The photoluminescene color of a poly(1b) solution in CH2Cl2 changed from green to red with Ar bubbling and rapidly returned to green by ceasing Ar bubbling. A poly(1b)-containing polymethyl methacrylate film exhibited a similar trend, as was observed for the polymer in solution. The weight residues of poly(1a) and poly(1b) at 800 °C were higher than that of poly(1).

DOI： 10.1021/acs.macromol.2c01882

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

N-(3,5-Diaminobenzoyl)-l-alanine dodecyl ester dihydrochlorides underwent gelation in tetrahydrofuran and CHCl₃. The gel emitted blue fluorescence in the sol state and green fluorescence in the gel state.

DOI： 10.1039/d3sm00299c

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Publishing type：Research paper (scientific journal)  

Optically active polymers and supramolecules that form well-defined assemblies and architectures are important materials with a wide range of applications. Among the variety of chiral building blocks for the preparation of optically active functional materials, amino acids and sugars stand out because of their versatile structures and functional groups. In these chiral units, intra- and intermolecular noncovalent interactions, such as hydrogen bonding and π-stacking, play significant roles in the generation of smart functions. This review summarizes the fabrication and functions of chiral conjugated polyacetylenes and polyarylene ethynylenes and chiral supramolecules based on these natural chiral compounds.

DOI： 10.1038/s41428-022-00677-1

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Polymeric metal complexes have attracted interest as polymer catalysts. In the present study, borane-2-(diphenylphosphino)-N-(4-ethynylphenyl)benzamide (1o) and borane-4-(diphenylphosphino)-N-(4-ethynylphenyl)benzamide (1p) were synthesized and polymerized using (nbd)Rh(PPh3)[C(Ph) = CPh2] as a catalyst. The BH3groups were removed from the formed polymers to obtain polyacetylenes with -PPh2ligands at the side chains, from which polymeric metal complexes were constructed by intermolecular and intramolecular coordination of platinum (Pt). The Pt-coordinating cross-linked network polymers were decross-linked by the addition of PPh3. The Pt-coordinating polymers catalyzed hydrosilylation of 1-dodecene with diethoxymethylsilane.

DOI： 10.1021/acs.macromol.2c00748

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

Platinum (Pt)-containing conjugated polymers were synthesized by the dehydrochlorination coupling polymerization of cis- and trans-dichlorobis(N-(p-(diphenylphosphino)benzoyl)-l-valine methyl ester)platinum(II) {cis-PtL2Cl2and trans-PtL2Cl2, L = P(Ph)2-p-C6H4CONHCH[CH(CH3)2]CO2CH3} with 1,4-diethynylbenzene, aiming at obtaining polymers with controlled geometry at the Pt centers. In the polymerization of cis-PtL2Cl2, the geometry at the Pt centers was controlled by the amine used in the polymerization and the reaction temperature. The formed polymer with trans-Pt centers exhibited a circular dichroism signal at the main chain chromophore region in CH2Cl2/MeOH mixed solvent. Based on the crystal packing state and non-covalent interaction analysis of a model compound, the chiroptical activity is attributed to aggregation stabilized by intermolecular π-π, CH-π, and hydrogen-bonding interactions between the phosphine ligands.

DOI： 10.1021/acs.organomet.2c00173

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acs.macromol.1c01773

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

The cured resins of ethynylene-linked mono-, di- and tri-functional benzoxazines were thermally more stable than the resins obtained from the analogous benzoxazines without a triple bond.

DOI： 10.1039/d2py00840h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

L-Tyrosine diketopiperazine (DKP) derivative 1 was synthesized, and the aggregation and photoluminescence behaviors were examined. A solution of 1 in tetrahydrofuran (THF) gradually became viscous at room temperature, and turned into the gel state 5 hours after preparation, as confirmed by dynamic viscoelasticity measurement. A solution of 1 in THF exhibited photoluminescence. Fibrous patterns were observed by transmission electron, atomic force and fluorescence microscopies. Dynamic light scattering, semiempirical molecular orbital and density functional theory calculations, as well as molecular dynamics simulations, indicated aggregate formation. This was attributed to intermolecular hydrogen bonding, mainly between the DKP moieties and partly between the urethane moieties, resulting in π-orbital overlap of the terminal phenyl groups leading to photoluminescence.

DOI： 10.1039/d1sm01206a

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acs.organomet.1c00435

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Language：English   Publishing type：Research paper (scientific journal)  

The topology of polymers affects their characteristic features, i.e., their microscopic structure and macroscopic properties. However, the topology of a polymer is usually fixed during the construction of the polymer chain and cannot be transformed after its determination during the synthesis. In this study, topology-transformable block copolymers that are connected via rotaxane linkages are introduced. We will present systems in which the topology transformation of block copolymers changes their 1) microphase-separated structures and 2) macroscopic mechanical properties. The combination of a rotaxane structure at the junction point and block copolymers that spontaneously form microphase-separated structures in the bulk provides access to systems that cannot be attained using conventional covalent bonds.

DOI： 10.1038/s41467-021-26249-0

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media {LLC}  

Benzoxazine polymers containing phenyleneethynylene and polypropylene glycol (PPG) in the main chain, poly(1)230, poly(1)400 and poly(1)2000, were synthesized by a Mannich reaction of the corresponding ethynylenebisphenol, paraformaldehyde and PPG diamines with Mn = 230–2,000. The curing temperature of poly(1) decreased from 212 to 182 °C as the Mn of the PPG chain decreased from 2,000 to 230. Poly(1)230–2000 was heated at 200–250 °C to obtain the corresponding polymers, and poly(1)′230–2000 was cured by ring-opening polymerization of the benzoxazine moieties. The structures of the polymers were elucidated by 1H-NMR and IR spectroscopies before and after curing. Poly(1)′230–2000 became flexible upon increasing the Mn of the PPG chain. Poly(1)′230 showed Tg as high as 253 °C. Poly(1)′230–2000 was thermally stable at approximately 300 °C, presumably due to the existence of rigid phenyleneethynylene moieties.

DOI： 10.1038/s41428-021-00568-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Rotaxane cross-linked polymers (RCPs) derived from ionic liquid monomer (ILm) and butyl acrylate were prepared through radical copolymerization in the presence of a vinyl-based rotaxane crosslinker. The developed RCPs exhibited superior mechanical properties compared to analogous network polymers prepared with conventional covalent crosslinkers. In addition, a small amount of ILm toughened the formed RCPs and increased their toughness. Moreover, the developed RCPs showed ionic conductivity in the order of 10(-7) S cm(-1) at 25 degrees C.

DOI： 10.1016/j.polymer.2021.123844

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media {LLC}  

A dinuclear Pd(II) complex possessing a cyclic ligand was applied as a coordinative cross-linker of acrylonitrile-butadiene rubber (NBR). Tensile tests revealed that the mechanical properties of the coordinatively cross-linked NBRs were improved compared with those of the original NBR. The effects of the loading amount of the complexes and their reusability were also investigated.A dinuclear Pd(II) complex possessing a cyclic ligand was applied as a coordinative cross-linker of acrylonitrile-butadiene rubber (NBR). Tensile tests revealed that the mechanical properties of the coordinatively cross-linked NBRs were improved compared with those of the original NBR. Increasing the loading amount of the complex enhanced Young's modulus, tensile strength, tensile strain, and toughness. The cross-linked NBR could be reused with a simple dissolution and drying process, which featured coordinative cross-linking.

DOI： 10.1038/s41428-020-00451-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Incorporation of rotaxane scaffolds into the crosslinking points of polymer networks significantly affects their rheological and mechanical properties. The present study involves the synthesis of a new rotaxane-type crosslinker containing nitrile N-oxide functional groups on both the axle and wheel components. The prepared crosslinker is highly reactive; however, it can be isolated and applied in the crosslinking reaction of a commercially important polymer, namely ethylene-propylene-butadiene monomer rubber (EPDM), in the absence of additives and catalysts. Tensile tests reveal that compared to a network containing conventional crosslinking points, both breaking strength and strain of the network structure prepared herein are improved due to the incorporation of movable crosslinking points. The synthesized network structure also exhibits five times higher fracture energy. The developed post-crosslinking methodology for the direct introduction of movable crosslinking points into pre-formed polymers will be valuable in the production of rotaxane materials for various applications.

DOI： 10.1002/marc.202000639

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/macp.202000459

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Nitrile N-oxides are useful reagents and crosslinkers for catalyst- and byproduct-free 1,3-dipolar cycloaddition reactions. The stability of nitrile N-oxides can be enhanced by introducing bulky substituents, whereas their reactivity decreases concomitantly. Herein, an isolatable aliphatic ditopic nitrile N-oxide was synthesized and applied to catalyst-free crosslinking of unsaturated bond-containing polymers. By decreasing the steric hindrance around the nitrile N-oxide moiety compared with a related crosslinker previously developed in our group, the operating temperature of the crosslinking reaction could be lowered. Efficient crosslinking of natural rubber (NR) was achieved at 40 degrees C in chloroform to give crosslinked NR without formation of byproducts. Furthermore, polyacrylonitrile and nitrile butadiene rubber can be used as the scaffolds for efficient catalyst- and solvent-free crosslinking reactions.

DOI： 10.1016/j.polymer.2020.123291

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

Ring-opening metathesis polymerization (ROMP) of norbornene derivatives is useful for preparing thermally stable and transparent polymeric materials with good moldability. This study deals with the ROMP of the norbornene monomer 1 bearing a platinum(Pt)-acetylide complex moiety using the Grubbs thirdgeneration catalyst. The product, poly(norbornene) [poly(1)], was investigated as a sensitizer for triplettriplet annihilation upconversion (TTA-UC), together with the copolymers of 1 and 2-norbornene 2. All the polymers exhibited bright photoluminescence under N-2. The phosphorescence of poly(1) was remarkably quenched, while that of poly(1-co-2)s was hardly quenched in CHCl3 solution. The phosphorescence of cast films of the polymers was highly responsive to oxygen, indicating possible application as oxygen sensing materials. The luminescence colors of the films were tunable between yellow and orange by copolymerization of 2 as a matrix. The polymers served as excellent sensitizers of TTA-UC with 9,10-diphenylanthracene as an emitter.

DOI： 10.1039/D1PY00665G

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

Ruthenium complexes Ru(MC33)(CO)_n(L)_2−n (L = H₂O, PPh₃, P(OEt)₃; n = 1, 2) with a pincer-type macrocyclic ligand MC33 with a cavity were synthesized and characterized.

DOI： 10.1039/D0NJ06133F

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

Chirally regulated pi-conjugated polymers containing platinum (Pt) complex moieties have great potential as chiroptically functional materials. In this study, novel platinum-containing conjugated polymers, poly(1a-2) and poly( 1b-2), were synthesized by the dehydrochlorination coupling polymerization of dichloro(4,4'-tertbutyl-2,2'-bipyridyl)platinum (1a) and dichloro(4,4'-dinonyl-2,2'bipyridyl)platinum (lb) with N-[ 3,5-bis(4-ethynylphenylethynyl)benzoyl] -L-alanine dodecylamide (2), and their chiral secondary structures in solutions were investigated. Poly(1a-2) exhibited bisignate circular dichroism (CD) signals assignable to the main chain chromophore (300-450 nm) in dimethylformamide (DMF)/MeOH = SO/SO (v/v). The presence of particles of Z-average = 30 nm was confirmed in this solution. These results indicated that poly (1a-2) formed chirally regulated aggregates. Single-crystal X-ray analysis of the model compound and density functional theory (DFT) calculations were carried out to examine the mode of aggregation of the polymers.

DOI： 10.1021/acs.macromol.0c00911

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/anie.202007866

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media {LLC}  

DOI： 10.1038/s41428-020-0370-5

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Other Link： http://www.nature.com/articles/s41428-020-0370-5

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

A novel benzoxazine derivative, 9,10-bis(6-ethynyl-3-pheny1-3,4-dihydro-1,3-benzoxazine)anthracene (1a), was synthesized by the Sonogashira-Hagihara coupling reaction of 9,10-dibromoanthracene and 6-ethynyl-3-phenyl-3,4-dihydro-1,3-benzoxazine. A CH2Cl2 solution of 1a luminesced with a high quantum yield (Phi = 81%). Compound 1a afforded solventinsoluble cross-linked polybenzoxazine 1b by the bulk polymerization at 250 degrees C. Solution polymerization of a dilute solution of 1a at 200 degrees C afforded solvent-soluble samples, accompanied by a decrease of photoluminescence intensity. The weight loss values of 1a and 1b were 81 and 87%, respectively, under nitrogen at 500 degrees C. We believe that the present study will lead to thermally stable curing resins whose degree of curing can be estimated with the naked eye by observing the decrease of photoluminescence.

DOI： 10.1021/acs.macromol.0c00910

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A novel air-stable, Cu-tethered macrocycle catalyst possessing a large inner cavity was successfully synthesized, creating a unique supramolecular catalytic system. The catalyst was utilized in the CO2-fixation reaction to propargylamines. The reaction proceeded more efficiently compared to the conventional CuI catalyst under atmospheric CO2 condition. Notably, owing to its topological effect, the Cu-tethered macrocycle catalyst exhibited unique substrate size selectivity. (C) 2020 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2020.151966

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A polystyrene-supported Pd complex bearing a cyclic pyridine-2,6-bisiamide ligand was synthesized and its catalytic activity in the Suzuki-Miyaura coupling reaction of 2,6-bromopyridine with 4-methoxyphenylboronic acid in aqueous media was investigated. The solid-supported catalyst exhibited catalytic activity and chemoselectivity that were comparable to those of homogeneous catalyst. The reusability of the solid-supported catalyst was also examined. (C) 2020 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2020.151870

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© 2020 Elsevier Ltd In this study, segmented polyurethanes (SPUs), including those with rotaxane structures, were synthesized in high yields (>83%) using a [2]rotaxane diol that has a hydroxy group in each wheel and axle component. The traditional prepolymer method was applied to introduce rotaxane structures at different locations in the soft segment and at the boundary between soft and hard segments. The mechanical properties of the formed SPUs were evaluated via tensile tests, and we determined that the introduction of an appropriate amount of rotaxane structure improved their extensibility, toughness, and stress-relaxing properties. Differential scanning calorimetry (DSC), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FT-IR), and synchrotron X-ray measurements revealed that the phase-separated structures of the SPUs were almost independent of the amount of rotaxane. The highly movable rotaxane scaffold was even effective for toughening the SPU, which is a physically cross-linked network, without changing their phase-separated structures.

DOI： 10.1016/j.polymer.2020.122358

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/asia.201901561

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：{MDPI} {AG}  

Silk composites with natural rubber (NR) were prepared by mixing degummed silk and NR latex solutions. A significant enhancement of the mechanical properties was confirmed for silk/NR composites compared to a NR-only product, indicating that silk can be applied as an effective reinforcement for rubber materials. Attenuated total reflection Fourier transform infrared (ATR-FTIR) and wide-angle X-ray diffraction (WAXD) analysis revealed that a β-sheet structure was formed in the NR matrix by increasing the silk content above 20 wt%. Then, 3,4-dihydroxyphenylalanine (DOPA)-modified silk was also blended with NR to give a DOPA-silk/NR composite, which showed superior mechanical properties to those of the unmodified silk-based composite. Not only the chemical structure but also the dominant secondary structure of silk in the composite was changed after DOPA modification. It was concluded that both the efficient adhesion property of DOPA residue and the secondary structure change improved the compatibility of silk and NR, resulting in the enhanced mechanical properties of the formed composite. The knowledge obtained herein should contribute to the development of the fabrication of novel silk-based elastic materials.

DOI： 10.3390/molecules25010235

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

A covalently crosslinked silk fibroin hydrogel (ChemSF) was successfully formed via an enzymatic crosslinking reaction using chemoenzymatically synthesized copolypeptides [poly(GPG(n)-r-Y-m)], which consist of a glycine-proline-glycine (GPG) tripeptide motif and tyrosine (Y), as linker molecules. The gelation time of ChemSF was effectively shortened to less than 100 seconds without loss of toughness by adding poly(GPG(n)-r-Y-m). In addition, the resilience of ChemSF was improved up to 86% at 66% strain, comparable to that of elastin, due to the flexible conformation of the poly(GPG(n)-r-Y-m) crosslinker. The acceleration of the gelation and the improvement of the resilience of ChemSF were simultaneously achieved by using a multifunctional peptide crosslinker.

DOI： 10.1039/D0PY00187B

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：FRONTIERS MEDIA SA  

Although the physical and biological functions of the skin layer of spider dragline have been studied and partially clarified, the morphology and elemental contents of the skin layer of silk fibers have not been investigated in detail to date. Here, the surface of Nephila clavata spider dragline was evaluated by field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) to obtain clear surface morphological and molecular information. The FE-SEM images of the spider dragline indicate that the spider dragline forms a bundle of microfibrils. This hierarchical structure might induce faint fibrilar and network-like patterns on the surface of the dragline. XPS analysis revealed the presence of Na, P, and S, which are reasonably explained by considering the biological components of the major ampullate gland of spiders. The results obtained here are preliminary but will be important to consider the molecular transition of silk proteins to form excellent hierarchical structures during the spider dragline spinning process.

DOI： 10.3389/fbioe.2020.00231

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

To evaluate the 'slide-ring' effect in a rotaxane cross-linked network, we incorporated mechanochromophores into static and rotaxane cross-linking points and compared the mechanochromisms exhibited by the obtained polymers. This novel strategy reveals a molecular-level phenomenon with visible color changes as well as enabling quantitative electron paramagnetic resonance measurements.

DOI： 10.1039/C9CC09452K

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

DOI： 10.1039/D0PY00278J

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acsbiomaterials.8b01309

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WILEY-V C H VERLAG GMBH  

Rotaxane-cross-linked polymers (RCP), which have rotaxane structures at the cross-link points, show unique physical properties originating from the movable cross-link points. Herein, poly(N,N-dimethylacrylamide) (PDMAAm) and poly(N-isopropylacrylamide) (PNIPAm) which are well known as hydrophilic polymers and whose glass transition temperatures are much higher than room temperature, were applied as matrix polymers for RCPs. These RCPs are easily and successfully synthesized by radical polymerization of vinyl monomers in the presence of small amounts of [2]rotaxane cross-linker (RC) comprising one wheel and one axle component with a methacrylate group on each component. As the result, PDMAAm-based RCP without any solvents and PNIPAm-based RCP swelled with water were much tougher than corresponding covalently cross-linked polymers. It is confirmed that RC endows both of the hard polymer networks and soft hydrogels with toughness.

DOI： 10.1002/masy.201800186

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/ange.201809171

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/anie.201809171

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Other Link： http://orcid.org/0000-0002-6170-0591

Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>A new synthetic route for obtaining polyfunctional nitrile <italic>N</italic>-oxides from OH-tethering nitrile <italic>N</italic>-oxide is reported.</p>

DOI： 10.1039/c8py00904j

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DOI： 10.1002/ange.201807261

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Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/cl.180477

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DOI： 10.1002/slct.201703073

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Publishing type：Research paper (scientific journal)   Publisher：RSC Polymer Chemistry Series  

DOI： 10.1039/9781788010108-00122

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Other Link： http://orcid.org/0000-0002-6985-4499

Publishing type：Research paper (scientific journal)   Publisher：Springer Nature  

DOI： 10.1038/s41428-018-0125-8

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/anie.201807261

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Mono-, di-, and trifunctional kinetically stabilized aliphatic nitrile N-oxides were synthesized via a two-step process comprising an initial nucleophilic addition of a heteroatomtethering and a carbon-centered nucleophile to a nitroethene and subsequent dehydration of the resultant nitroalkane. We further present the first X-ray crystal structure investigation of an aliphatic nitrile N-oxide. The kinetics of the products' click reactions and DFT calculations confirmed that the obtained nitrile N-oxides had high reactivities.

DOI： 10.1246/cl.161098

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The polymer nitrile N-oxide containing poly(ethylene glycol) (PEG) skeleton PEG-CNO was synthesized via a stepwise reaction. The catalyst-free click reaction of PEG-CNO with terminal CvC bond-tethering compounds afforded the corresponding diblock and multi-arm star polymers in high yields. The click reactions under solvent-free conditions resulted in significant rate acceleration and high yields of the polymers.

DOI： 10.1039/c7py00100b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Native -cyclodextrin- (-CD) and permethylated -CD (PMeCD)-based rotaxanes with various short alkylene chains as axles can be synthesized through a urea end-capping method. Native -CD tends to form [3]- or [5]pseudorotaxanes and not [2]- or [4]pseudorotaxanes, which indicates that the coupled CDs act as a single fragment. End-capping reactions of the pseudorotaxanes with C18 and C24 axle lengths do not occur because the axle termini are covered by the densely stacked CDs. The number of PMeCDs on the pseudorotaxane is flexible and mainly depends on the axle length. Peracetylated -CD (PAcCD)-based rotaxanes are synthesized through O-acetylation of the -CD-based rotaxanes without any decomposition of the rotaxanated structures. The structures of PMeCD-based [3]- and [4]rotaxanes, and the molecular dynamics calculations on [3]pseudorotaxanes, indicate that the tail face of PMeCDs is regularly directed toward the axle termini. On the basis of the results obtained, it can be concluded that the directions and numbers of CDs in rotaxanes containing short alkylene chains depend on 1)the interactions between CDs, 2)the length of the alkylene axle, and 3)the interactions between the axle end and tail face of the CD.

DOI： 10.1002/chem.201504882

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The thermotriggered modification of surfaces was performed under catalyst-free conditions using an orthogonal agent possessing both nitrile N-oxide and Meldrum's acid moieties. The nitrile N-oxide moiety of the orthogonal agent successfully underwent catalyst-free 1,3-dipolar cycloaddition to unsaturated bonds of glass surfaces to produce Meldrum's acid-functionalized surfaces. The subsequent thermal decomposition of Meldrum's acid moiety in the presence of nucleophiles afforded versatile nucleophile-modified surfaces (e.g., wet, waterproof, and photoactive surfaces). Surface characteristics were investigated with the water contact angle, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS). In addition, the surface modification of silica nanoparticles using the orthogonal agent was also achieved to evaluate the density of the functional group concentration on the surface.

DOI： 10.1021/acs.langmuir.5b03881

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Vinylic supramolecular cross-linkers (VSCs) were prepared by mixing an alpha-cyclodextrin dimer or a trimer and a polyethylene glycol-type macromonomer. DOSY NMR study exhibited the size of VSC and its dependency on the concentration and the structure of the components. Polymerization of a vinyl monomer with VSC afforded rotaxane cross-linked polymers.

DOI： 10.1039/c6py00367b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

DOI： 10.1038/pj.2015.34

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/chem.201590073

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Polymeric quaterthiophenes containing optically active C-2-chiral spirobifluorene skeletons were synthesized as a new type of helical foldamers, and their higher-order structures were investigated. Oxidization of quaterthiophene moieties caused the spacer units to be in planar structure, leading the conformation of the polymer to be a coil-shaped, rigid helix. This transformation was reversibly performed.

DOI： 10.1021/acsmacrolett.5b00176

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Palladium-containing macrocycle catalysts (PdMCs) with different ring sizes ranging from 24 to 30 members were synthesized. The intramolecular hydroamination of an allylurethane (AU) catalyzed by PdMCs proceeded efficiently to afford the corresponding oxazolidinone (OZ) in 95% isolated yield. The dependence of the hydroamination of AU to OZ on the cavity size indicated that the reaction rate was clearly controlled by both substrate uptake and product release steps.

DOI： 10.1021/acs.orglett.5b00378

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A series of new photo-responsive amino acid-derived azobenzenedicarboxylic acid derivatives (S)-1a-e were synthesized. Compound (S)-1a in the trans form exhibited no circular dichroism (CD) signal in DMF under ambient conditions, whereas intense Cotton effects were observed upon UV irradiation, indicating the formation of a chiral supra-molecular structure in the cis form. The CD signals disappeared when trifluoroacetic acid (TFA) was added to the solution. The ester counterpart [(S)-1a'] showed no CD signal. Hydrogen bonding between the carboxy groups seemed necessary for constructing the supramolecular structure. The kinetic studies of cis to trans isomerization of (S)-1a demonstrated that the formation of a chiral supramolecule enhances the stability of the cis-azobenzene structure. The ESI mass spectrum of stilbenedicarboxylic acid (S)-4, an analogue of (S)-1b, confirmed the formation of a dimer. A theoretical CD study revealed that (S)-1a in the cis form should be present as a cyclic chiral dimer.

DOI： 10.1002/chem.201406054

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Two types of one-handed exact helical polymers, coil- and screw-shaped polymers, were synthesized by the two-point-covalent-linking protocol using C-2-chiral spirobifluorene (SBF) and C-2- or C-s-symmetric anthraquinone spacers. Central to this protocol is a new aromatic ring-forming reaction based on the stepwise reductive cyclization of bis(aryloxy group)-substituted anthraquinone derivatives. The helical structures of the polymers annulated by aromatic skeletons exhibited high thermal stability attributed to the rigid C-2-chiral SBF units and the covalently two-point-connected structure.

DOI： 10.1039/c5cc02086g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The Sonogashira-Hagihara coupling polymerization of D-hydroxyphenylglycine-based diiodo monomers 1 and 2 with p-diethynylbenzene gave novel optically active poly(phenyleneethynylene)s 3 and 4 bearing perylene moieties with number-average molecular weights (M-n's) of 4800 and 3700 in 39% and 57% yields. The CD and UV-vis spectroscopic analysis revealed that polymer 3 formed folded helical structures in various solvents, while polymer 4 did not. UV-vis and fluorescence spectroscopic analysis indicated the presence of energy transfer from the phenyleneethynylene main chain to perylene side chains.

DOI： 10.1246/cl.140601

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The acetylenic coupling polymerization of D-hydroxyphenylglycine-derived m-terphenylene diynes 1-5 using Pd/Cu catalyst gave the corresponding polymers [poly(1)-poly(5)] with M-n = 12 000-60 000 in 53-89% yields. The polymers were soluble in THF and DMF. CD and UV-vis spectroscopic analysis revealed that p,p'-phenyleneethynylene-linked poly(1), poly(3), and poly(5) formed chiral higher-order structures in THF/H2O mixtures, while m,m'-phenyleneethynylene-linked poly(2) and poly(4) did not. The sign of CD signal of poly(1) was reasonably predicted by time-dependent density functional calculations of the model system. The polymers emitted fluorescence with quantum yields ranging from 0.2-14.8%.

DOI： 10.1021/ma402123w

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Language：English   Publishing type：Research paper (scientific journal)  

Novel optically active poly(phenyleneethynylene-aryleneethynylene)s bearing hydroxy groups with various arylene units [poly(1-2), poly(1-3a), poly(1-3b), poly(1-4)] were synthesized by the Sonogashira-Hagihara coupling polymerization of (S)-3,5-diiodo-4-hydroxy-C6H4CONHCH(CH 3)COOC12H25 (1) with HCî -C-Ar-Cî -CH [2 (Ar = 1,4-phenylene), 3a (Ar = 2,7-naphthylene), 3b (Ar = 1,4-naphthylene) and 4 (Ar = 1,6-pyrenylene), and the optical properties were compared. Polymers with number-average molecular weights (Mn) of 5,300-11,300 were obtained in 88-94% yields. CD and UV-vis spectroscopic analysis revealed that all the polymers formed predominantly one-handed helical structures in THF. The order of absorption maxima (λmax) of the polymers was poly(1-3a) < poly(1-2) < poly(1-3b) < poly(1-4). Poly(1-2), poly(1-3a), poly(1-3b), and poly(1-4) emitted blue, purplish blue, green and yellow fluorescence, respectively. © 2013 American Chemical Society.

DOI： 10.1021/ma401730e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Novel optically active poly(m-phenyleneethynylene-aryleneethynylene)s bearing hydroxy groups with various arylene units {poly[(S)-/(R)-1-3a]-poly[(R)-1-3e] and poly[(S)-2-3a]} were synthesized by the Sonogashira-Hagihara coupling polymerization of 3,5-diiodo-4-hydroxy-C6H4CONHCH(CH3)COXC12H25 [(S)-/(R)-1 (X = O), (S)-2 (X = NH)] with HC C Ar-C CH [3a (Ar = 1,4-C6H4), 3b (Ar = 1,4-C6H4-1,4-C6H4-), 3c (Ar = 1,4-C6H4-1,4-C6H4-1,4-C6H4-), 3d (Ar = 2,5-dihexyl-1,4-C6H2), 3e (Ar = 2,5-didodecyl-1,4-C6H2)]. The yields and number-average molecular weights of the polymers were in the ranges 60-94% and 7,000-29,500 with no correlation between the yield and the M-n. Circular dichroism (CD), UV-vis, and fluorescence spectroscopic analyses indicated that poly[(S)-1-3a] poly[(S)-1-3c] and poly[(S)-2-3a] formed predominantly one-handed helical structures in THF, while poly[(S)-1-3d] and poly[(S)-1-3e] showed no evidence for forming chirally ordered structures. All polymers emitted blue fluorescence. The solution state IR measurement revealed the presence of intramolecular hydrogen bonding between the amide groups at the side chains of poly[(S)-1-2a]. The helical structures and helix-forming abilities of the polymers were analyzed by the molecular mechanics (MM), semiempirical molecular orbital (MO) and density functional theory (DFT) methods. Tube-like structures, presumably formed by perpendicular aggregation of the helical polymers, were observed by atomic force microscopy (AFM).

DOI： 10.1021/ma4017295

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Language：English   Publishing type：Research paper (scientific journal)  

Novel optically active poly(phenyleneethynylene)s bearing azobenzene moieties in the main chains [poly(1-2m), poly(1-2p)] were synthesized by the Sonogashira-Hagihara coupling polymerization of 3′,5′-diiodo- 4′-hydroxy-N-α-tert-butoxycarbonyl-d-phenylglycine hexylamide (1) with 3,3′-diethynylazobenzene (2m) and 4,4′-diethynylazobenzene (2p). The corresponding polymers [poly(1-2m), poly(1-2p)], with number-average molecular weights of 10700 and 9400, were obtained in 70% and 86% yields, respectively. CD and UV-vis spectroscopic analyses revealed that poly(1-2m) and poly(1-2p) formed predominantly one-handed helically folded structures in CHCl3/THF mixtures. Poly(1-2m) underwent a reversible conformational change between folded and unfolded structures upon UV and visible irradiation, as a result of trans-cis isomerization of the azobenzene moieties. On the other hand, poly(1-2p) showed very little conformational transformation or azobenzene isomerization. The formation of helical structures was supported by conformational analysis based on the molecular mechanics (MM), semiempirical molecular orbital (MO), and density functional theory (DFT) methods. © 2013 American Chemical Society.

DOI： 10.1021/ma4002947

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Novel poly(m-phenyleneethynlene-p-phenyleneethynylene)s bearing polymerizable diene or norbornene groups were synthesized by the Sonogashira-Hagihara coupling polymerization of the corresponding D-hydroxyphenylglycine-derived diiodo monomers with p-diethynylbenzene. These polymers exhibited strong Cotton effects derived from a predominantly one-handed helical conformation in CHCl3 and tetrahydrofuran, but exhibited weak or no Cotton effects in N,N-dimethylformamide. The metathesis polymerization of the diene and norbornene moieties was performed at the side chains of the polymers under diluted conditions in the presence of a chain-transfer agent, if necessary. The reaction took place intramolecularly, which was confirmed by size exclusion chromatography (SEC) measurements. The polymers exhibited stronger Cotton effects even in polar media after the intramolecular crosslinking, which indicated stabilization of the predominantly one-handed helical structures. (c) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2012.04.028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Novel optically active substituted acetylenes HC? CCH2CR1(CO2CH3)NHR2 [(S)-/(R)-1: R1 = H, R2 = Boc, (S)-2: R1 = CH3, R2 = Boc, (S)-3: R1 = H, R2 = Fmoc, (S)-4: R1 = CH3, R2 = Fmoc (Boc = tert-butoxycarbonyl, Fmoc = 9-fluorenylmethoxycarbonyl)] were synthesized from a-propargylglycine and a-propargylalanine, and polymerized with a rhodium catalyst to provide the polymers with number-average molecular weights of 240038,900 in good yields. Polarimetric, circular dichroism (CD), and UVvis spectroscopic analyses indicated that poly[(S)-1], poly[(R)-1], and poly[(S)-4] formed predominantly one-handed helical structures both in polar and nonpolar solvents. Poly[(S)-1a] carrying unprotected carboxy groups was obtained by alkaline hydrolysis of poly[(S)-1], and poly[(S)-4b] carrying unprotected amino groups was obtained by removal of Fmoc groups of poly[(S)-4] using piperidine. Poly[(S)-1a] and poly[(S)-4b] also exhibited clear CD signals, which were different from those of the precursors, poly[(S)-1] and poly[(S)-4]. The solution-state IR measurement revealed the presence of intramolecular hydrogen bonding between the carbamate groups of poly[(S)-1] and poly[(S)-1a]. The plus CD signal of poly[(S)-1a] turned into minus one on addition of alkali hydroxides and tetrabutylammonium fluoride, accompanying the red-shift of ?max. The degree of ?max shift became large as the size of cation of the additive. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

DOI： 10.1002/pola.25975

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The Sonogashira-Hagihara coupling polymerization of 3',5'-diiodo-4'-hydroxy-N-alpha-tert-butoxycarbonyl-D-phenylglycine ethyl-, hexyl-, and laurylamides 1a-c with p-nonsubstituted, cyano, hexyl, and methoxy 3,5-diethynylazobenzenes 2a-d was carried out to obtain optically active novel poly(m-phenyleneethynylene) with M-w values in the range from 6900 to 15 400 in 62-84% yields. CD and UV-vis spectroscopic data indicated that the polymers adopted thermally stable helical conformations in CH2Cl2 and N,N-dimethylformamide. Poly-(1b-2a) further formed a chirally aggregated structure. The azobenzene moieties of the polymers underwent reversible photoisomerization upon UV- and visible-light irradiation, accompanying the changes of the higher-order structures.

DOI： 10.1021/ma200281e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The Sonogashira-Hagihara polymerization of 3',5'-diiodo-N-alpha-tert-butoxycarbonyl-L-tyrosine methyl ester (1) and 3',5'-diiodo-N-alpha-tert-butoxycarbonyl-O-methyl-L-tyrosine methyl ester (2) with para-diethynylbenzene (3) was carried out to obtain optically active poly(m-phenyleneethynylene-p-phenyleneethynylene)s [poly(1) and poly(2)] with M-n's ranging from 9900 to 15,000 in 80-87% yields. Poly (1) exhibited intense CD signals in DMSO and THF, but did not in CH2Cl2, indicating that it took a predominantly one-handed helical conformation in the former two solvents. On the other hand, there was no evidence for poly(2) to take a helical structure in these solvents. Poly(1) turned the CD sign at 390 nm from plus to minus in DMSO/H2O = 9/1 (v/v) by the addition of NaOH. Alkaline hydrolysis of ester moieties of poly(1) and poly(2) gave the corresponding polymers having carboxy groups [poly(1a) and poly(2a)]. Poly(1a) and poly(2a) increased the CD intensity by the addition of NaOH. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2010.03.048

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Novel conjugated polymers containing 3,9-carbazolylene and silylenevinylene moieties were synthesized by the hydrosilylation polymerization of 1,4-bis(3-ethynyl-9-carbazolyl)benzene (1) with various bis(hydrosilane)s or dihydrosilanes using a rhodium catalyst. Polymers with weight-average molecular weights ranging from 5400 to 20,000 were obtained in 55-97% yields by the polyaddition with a rhodium catalyst in toluene at 25 degrees C for 24 h. All the polymers were soluble in CHCl3 and THF, and had predominantly trans-structures. The polymers exhibited lambda(max) at a longer wavelength region than 1, and emitted fluorescence in 14-50% quantumn yields. The polymers were oxidized and reduced in the region of 0.4-1.6 V, and thermally stable up to 200 C under air. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1815-1821, 2010

DOI： 10.1002/pola.23950

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Optically active azobenzenedicarboxylic acids were synthesized from l-alanine, and the polycondensation of the diacids with o-, m-, p-xylylenediols, 5-norbornene-2,3-endo,endo- and exo,exo-dimethanols, m-, p-xylylenediamines, and trans-1,4-cyclohexanediamine was carried in N,N-dimethylformamide. Polymers with weight-average molecular weights of 3,300-33,700 were obtained in 63%-quantitative yields. All the polymers reversibly isomerized the azobenzene units from trans to cis and vice versa upon UV- and visible-light irradiations. The polymers exhibited no evidence for the formation of a chiral secondary structure.

DOI： 10.1007/s00289-009-0121-4

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