Synthesis and Curing Behaviors of Cross-Linkable Polynaphthols from Renewable Resources: Preparation of Artificial Urushi

Precision synthesis of 3-substituted urushiol analogues and the realization of their urushiol-like performance

Urushiol is a resource-limited natural coating material with diverse applications; however, the synthesis of urushiol analogues and the realization of their urushiol-like performance remain challenging. Herein, four urushiol analogues, namely, 3-((4-alkenoylpiperazin-1-yl)methyl)catechols with the precise 3-substitution pattern on a catechol as that found in urushiol were synthesized by employing the Mannich reaction of catechol with formaldehyde and N-Boc-piperazine as the key step in a two-step route. By using optimization, the advantages of convenience in operation, cost-effectiveness, and scalability could be obtained. The electropolymerization of these analogues on copper was found to be practical due to their higher aerobic stability than urushiol, affording robust coatings with desirable hardness, adhesion strength, hydrophobicity, and thermal stability. Furthermore, the coatings exhibited effective corrosion protection on copper with initial anticorrosion efficiency up to 99.9% and comparatively higher efficiency (more than 97%) after 4 weeks of immersion in 3.5 wt% NaCl solution. The evidence from the electrochemical and infrared spectroscopic characterization data revealed that the electropolymerization process mechanically involved the free radical coupling of phenoxyl radicals to themselves and to the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bonds in the side chain, forming a robust crosslinking coating. This work paves a way for the synthesis of high-performance urushiol analogues with potential applications as metal protection materials.

Regioselective Mannich reaction was performed on catechol, yielding 3-substituted urushiol analogues that could be electropolymerized to achieve the desirable urushiol-like performance.

Enzymes as Green Catalysts for Precision Macromolecular Synthesis

The present article comprehensively reviews the macromolecular synthesis using enzymes as catalysts. Among the six main classes of enzymes, the three classes, oxidoreductases, transferases, and hydrolases, have been employed as catalysts for the in vitro macromolecular synthesis and modification reactions. Appropriate design of reaction including monomer and enzyme catalyst produces macromolecules with precisely controlled structure, similarly as in vivo enzymatic reactions. The reaction controls the product structure with respect to substrate selectivity, chemo-selectivity, regio-selectivity, stereoselectivity, and choro-selectivity. Oxidoreductases catalyze various oxidation polymerizations of aromatic compounds as well as vinyl polymerizations. Transferases are effective catalysts for producing polysaccharide having a variety of structure and polyesters. Hydrolases catalyzing the bond-cleaving of macromolecules in vivo, catalyze the reverse reaction for bond forming in vitro to give various polysaccharides and functionalized polyesters. The enzymatic polymerizations allowed the first in vitro synthesis of natural polysaccharides having complicated structures like cellulose, amylose, xylan, chitin, hyaluronan, and chondroitin. These polymerizations are "green" with several respects; nontoxicity of enzyme, high catalyst efficiency, selective reactions under mild conditions using green solvents and renewable starting materials, and producing minimal byproducts. Thus, the enzymatic polymerization is desirable for the environment and contributes to "green polymer chemistry" for maintaining sustainable society.

Direct Synthesis of ESBO Derivatives-18O Labelled with Dioxirane

This work addresses a new approach developed in our laboratory, consisting in the application of isolated dimethyldioxirane (DDO, 1a) labelled with ¹⁸O for synthesis of epoxidized glyceryl linoleate (Gly-LLL, 2). We expect that this work could contribute in improving analytical methods for the determination of epoxidized soybean oil (ESBO) in complex food matrices by adopting an ¹⁸O-labelled-epoxidized triacylglycerol as an internal standard.

Dielectric properties of castor oil cross-linked polyurethane

A series of polyurethanes cross-linked with castor oil were synthesized and the influence of the polyurethane chemical structure on molecular relaxations in such systems was determined. Three different castor oil rates were used in the synthesis of the cross-linked polyurethane chains. These cross-linked polyurethanes were compared with a linear polyurethane which was obtained by chain extension with 1,4-butane diol. The dielectric properties and relaxation phenomena of the polyurethane were studied as a function of the hard segment structure and cross-linker content as structural variables and frequency and temperature as experimental variables. It was found that the formation of hydrogen bonds between urethane groups of physical networks may control the molecular mobility, but the chemical nature and content of the cross-links of the hard segments strongly influences the molecular relaxation. The relaxation peaks were observed in the temperature range of -65 to 60°C for polyurethane with different cross-linked segment contents, peaks which shifted to high temperature with the increase in frequency.

Synthesis and analysis of resorcinol-acetone copolymer

Synthesis and characterization of resorcinol-acetone copolymer is described. The polymer was prepared by trifluoroacetic acid-catalyzed polymerization of resorcinol with acetone. According to the (1)H-NMR, (13)C-NMR, and MALDI-TOF Mass spectra data, the obtained polymer had three types of repeating units: isopropylidene bridged-resorcinol, chromane ring, and spiro-shaped double chromane ring, indicating that polymerization proceeded via simultaneous addition-condensation and cyclization of resorcinol with acetone. The obtained polymer can be useful not only for the development of plastic materials such as thermosets, adhesives, and coatings but also for the synthesis of biomaterials such as antimicrobial agents, pesticides, and medicines.