Makoto Takeishi

Effective microbial production of poly(4-hydroxybutyrate) homopolymer by Ralstonia eutropha H16

The effective microbial production of copolyesters of 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB) with high mole fractions of 4HB units by a wild-type strain of Ralstonia eutropha H16 was investigated in culture solutions containing 4-hydroxybutyric acid (4HBA) and various carbon substrates in the presence of a nitrogen source such as ammonium sulfate. The addition of glucose or acetic acid to the culture solution containing 4HBA in the presence of ammonium sulfate resulted in the production of random copolymers of P(3HB-co-4HB) with compositions of up to 82 mol% 4HB, but the yield of copolymers was less than 7 wt% of dried cell weights. In contrast, when n-alkanoic acids such as propionic acid, butyric acid, valeric acid and hexanoic acid, being subject to β-oxidation metabolism in the cell, were used as the co-substrates of 4HBA in the presence of ammonium sulfate, a mixture of copolymers with two different 4HB compositions was produced, and copolyesters with compositions of 93–100 mol% 4HB were isolated from chloroform–n-hexane insoluble fractions in the mixture of copolymers. Especially, when this wild-type Ralstonia eutropha H16 was cultivated in a medium containing 4HBA (15 g litre−1), propionic acid (5 g litre−1) and ammonium sulfate (5 g litre−1), namely C/N (mol/mol) = 10, the P(4HB) homopolymer was produced at maximally 34 wt% of dry cell weight (7.8 g litre−1), and the conversion yield of 4HBA to P(4HB) homopolymer resulted in values as high as 21 mol%. © 1999 Society of Chemical Industry

Stereospecific interaction of one-handed helical polycations with chiral anions

Abstract Optically active polyamide helices were obtained by the reaction of axially dissymmetric (R)- or (S)-6,6′-dibromo-2,2′-diethoxy-1,1′-binaphthyl, 3,6-diaminoacridine (proflavine), and carbon monoxide using a palladium catalyst. The acridine units in the chiral backbone were protonated with chiral 10-camphorsulfonic acid. Circular dichroism measurements revealed that (R)-(−)-camphorsulfonate anion ((R)-(−)-CSA−) is more easily incorporated into the protonated right-handed polyamide helix than (S)-(+)-camphorsulfonate anion ((S)-(+)-CSA−) and that the left-handed cationic helix preferentially interacts with (R)-(−)-CSA− to (S)-(+)-CSA−.

Synthesis of polysiloxane‐grafted fluoropolymers and their hydrophobic properties

A polydimethylsiloxane with an epoxide end group was grafted onto a fluoropolymer that had hydroxyl side chains by using protonic or Lewis acids as catalysts. Strong acids such as trifluoromethanesulfonic acid were found to be effective for the grafting of the polydimethylsiloxane of relatively large molecular weight (Mn 4440). A coating prepared from the graft polymer was so hydrophobic that a water droplet of 10 μL slid down on its inclined plane surface (30° with respect to the horizontal). ESCA analysis revealed that the siloxane branches are preferentially present on the surface.

Unsteady stirring method used in suspension polymerization of styrene

An unsteady stirring method, that is, coreverse rotation with different periodic intervals, was adopted to the suspension polymerization of styrene. Experiments were carried out in a 0.5-L flat-bottom flask with a six-blade Rushton turbine. Parameters affecting the final particle size and the particle size distribution under the unsteady stirring conditions, such as the agitation speed and the periodic interval, had been studied in detail, and the results were compared with those under a steady stirring one. The experimental results showed that the average particle size decreased and the uniformity final particle size distribution could be significantly improved when unsteady stirring approach is used. These were explained as the result of the decrease of the coalescence rate during the suspension polymerization when the unsteady stirring method was used.

Polymerization of – Phenylmaleimide Initiated by 9‐Borabicyclo[3.3.1]nonane

N-Phenylmaleimide (N-PMI) was polymerized by 9-borabicyclo[3.3.1] nonane (9-BBN) in tetrahydrofuran under argon at 0°C. The molecular weight distributions of the resulting polymers were around 1.1. The rate of polymerization was proportional to [9-BBN] 1.18 and [N-PMI] 1.24 . Hydroquinone had little effect on the rate of polymerization and on the molecular weight of the polymers obtained. Triethylamine completely inhibited the polymerization, and aniline with a relatively small pK a value and zinc iodide effectively retarded the polymerization. The polymerization did not proceed either in polar dimethylformamide or in non-polar toluene. In polymerizations at temperatures higher than 60°C the conversions decreased. On the basis of the results, a non-radical mechanism was proposed for this polymerization.

Rate enhancement of amines in the photopolymerization of methyl methacrylate under oxygen

The photopolymerization of methyl methacrylate was accelerated by amines such as N,N-dimethylbenzylamine, triethylamine, and diethylamine under nitrogen, in which additional initiating radicals were generated by the reaction of the amines with excited MMA. Enhanced rates were observed under oxygen for this photopolymerization in the presence of amines. Because UV spectra of the amines under oxygen indicated that the amines form charge-transfer complexes with oxygen, the rate enhancement was ascribed to photodecomposition of complexes that yield radical species. Molecular weights of polymers obtained in the photopolymerization in the presence of amines decreased under oxygen, supporting the assumed mechanism.

Oxygen-accelerated photopolymerization of methyl methacrylate in the presence of amides

Abstract The photopolymerization of methyl methacrylate (MMA) was accelerated by amides such as N-methylpyrrolidone (NMP), pyrrolidone (PD), and dimethylacetamide (DMA) in the following order: NMP > PD > DMA. the rates of photopolymerization of styrene and vinyl acetate were also increased by NMP. the results suggest that the free radicals produced by the photodecomposition of these amides initiate the polymerization. Moreover, the rate of photopolymerization of MMA in the presence of the amides was enhanced by oxygen after an induction period. the UV absorption spectra of these amides were measured under nitrogen and oxygen; the extra absorptions observed under oxygen were ascribed to charge-transfter complexes between oxygen and the amides. the reaction mechanism is discussed on the basis of the photoreaction of the complex

Group Selective Linear Polymerization of Vinyl Acrylate Using19-Borabicyclo[3.3.1]nonane

Vinyl acrylate (VA) was polymerized with 9-borabicydo[3.3.1]nonane (9-BBN) in tetrahydrofuran under argon at low temperatures (to -60°C). Hydroquinone and 2,6-di-tert-butyl-p-cresol had little effect on the polymerization. Addition of tetrachloromethane as a radical chain transfer agent did not lead to decrease in molecular weight of the polymer obtained. The initial rate of polymerization was proportional to [9-BBN] 0.91 and [VA] 1.37 . The experimental results were indicative of non-radical properties of the propagating chain end. The polymer was soluble in organic solvents such as toluene, chloroform and N,N-dimethylformamide. The nuclear magnetic resonance measurements showed the presence of pendant vinyl groups in the polymer, indicating that only the acrylic double bond of VA reacted for polymerization to yield a linear polymer. Aniline retarded the polymerization and no polymer was formed in the presence of triethylamine. These inhibitory effects were explained on the basis of complex formation of 9-BBN with amines. This polymerization is discussed in terms of a non-radical mechanism.

Polymerization of α,β‐unsaturated carbonyl monomers initiated by 9‐borabicyclo [3.3.1] nonane

9-Borabicyclo[3.3.1]nonane (9-BBN) initiated the polymerization of α,β-unsaturated carbonyl monomers such as ethyl acrylate (EA) without an oxidant at low temperatures (to - 90°C) under argon. Hydroquinone and 2,6-di-tert-butyl-p-cresol had little effect on the polymerization, indicating that the propagating chain end is not a free radical. The rate of polymerization was found to be proportional to [9-BBN] 1.0 and [EA] 1.5 . Electron spin resonance measurements using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap showed the absence of any radical species under polymerization conditions. No copolymerization of EA with styrene occurred. On the basis of the results obtained, this polymerization was assumed to proceed via a non-radical mechanism.

Photosensitized degradation of poly(α-chloroacrylonitrile) under oxygen

Abstract Poly(α-chloroacrylonitrile)(PCAN) degraded upon irradiation with a xenon lamp under oxygen in the presence of 9,10-dicyanoanthracene (DCA) and trans-stilbene (TS), and a similar degradation was observed for the reaction of the polymer with potassium superoxide (KO2). The IR spectra of the polymers recovered in both cases were almost the same. The mechanism of the photodegradation of PCAN was interpreted as follows: excited DCA accepts an electron from TS and the radical anion of DCA formed transfers an electron to oxygen, generating “superoxide anion (O2 −),” which reacts with PCAN to decompose the polymer.