Hiromitsu Sogawa

Synthesis and characterization of supramolecular cross-linkers containing cyclodextrin dimer and trimer

Vinylic supramolecular cross-linkers (VSCs) were prepared by mixing an α-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.

Structural Analysis and Inclusion Mechanism of Native and Permethylated α-Cyclodextrin-Based Rotaxanes Containing Alkylene Axles

Native α-cyclodextrin- (α-CD) and permethylated α-CD (PMeCD)-based rotaxanes with various short alkylene chains as axles can be synthesized through a urea end-capping method. Native α-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 α-CD (PAcCD)-based rotaxanes are synthesized through O-acetylation of the α-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.

Thermotriggered Catalyst-Free Modification of a Glass Surface with an Orthogonal Agent Possessing Nitrile N-Oxide and Masked Ketene Functions

The thermotriggered modification of surfaces was performed under catalyst-free conditions using an orthogonal agent possessing both nitrile N-oxide and Meldrums 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 Meldrums acid-functionalized surfaces. The subsequent thermal decomposition of Meldrums 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.

Synthesis and Cavity Size Effect of Pd-Containing Macrocycle Catalyst for Efficient Intramolecular Hydroamination of Allylurethane

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.

Preparation of a highly reactive polymer click reagent, PEG nitrile N-oxide, and its application in block and star polymer synthesis

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 CC 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.

DBU-catalyzed CO 2 fixation in polypropargylamines under solvent-free conditions

Solvent-free base-catalyzed CO2 fixation into polymers having 2-pyridyl group-substituted propargylamine moieties in the main and side chains was achieved under atmospheric CO2 condition. The reactivity of the polymer films was improved by the introduction of pendant tertiary amine moiety.

New synthetic route to OH-functionalized nitrile N-oxide and polyfunctional nitrile N-oxides for click crosslinking and decrosslinking of natural rubber

A new synthetic route for obtaining polyfunctional nitrile N-oxides from OH-tethering nitrile N-oxide is reported. OH-Tethering nitrile N-oxide is synthesized using the proposed route by using an intermediary nitroalkane and derived to polyfunctional ones via OH-involving condensations. The polyfunctional nitrile N-oxides undergo a catalyst-free crosslinking reaction to form crosslinked natural rubber (NR). The physical properties of the crosslinked NR indicate the occurrence of effective crosslinking. A crosslinker with ester-connected two nitrile N-oxide functions is demonstrated to have favorable decrosslinking ability.

Cyclodextrin‐Based [3]Rotaxane‐Crosslinked Fluorescent Polymer: Synthesis and De‐Crosslinking Using Size Complementarity

Vinyl-group-substituted, α-cyclodextrin-based, size-complementary [3]rotaxanes were synthesized as crosslinkers for rotaxane-crosslinked poly(methyl methacrylate) (RCP) by radical polymerization. The size complementarity of the crosslinkers made it possible to de-crosslink the RCP by heating, and the degree of decoupling was monitored by fluorescence intensity, depending on the state of the axle component of the rotaxane crosslink moiety.