Showing papers by "Yoshiharu Kimura published in 1997"

Solid-State Postpolymerization of l-Lactide Promoted by Crystallization of Product Polymer: An Effective Method for Reduction of Remaining Monomer

Abstract: Solid-state postpolymerization of l-lactide was studied by two different ways with 0.1 mol % of stannous 2-ethyl hexanoate as the catalyst. In a two-step method, the ordinary melt polymerization of l-lactide was first performed at temperatures higher than the crystallization temperature (Tc) of poly(l-lactide) (PLLA), and then the postpolymerization was continued around the Tc of PLLA. As PLLA crystallized in the second stage (e.g., when the temperature was changed from 140 to 120 °C), the monomer consumption was found to reach 100% because the monomer and catalyst could be concentrated in the amorphous part. Without the crystallization of PLLA occurring in the postpolymerization, a homogeneous supercooling state was formed to have a remaining monomer ratio exceeding 5 wt %. In the alternative one-step method where the polymerization was continued around the Tc of PLLA, the polymer crystallization was induced during the polymerization to promote the monomer consumption to reach 100%. The kinetic analysis ...

Surface and morphological characterization of polysiloxane‐block‐polyimides

Abstract: Two series of polysiloxane-block-polyimides were synthesized by the method of solution imidization of the polyamic acids prepared from the dianhydride/diamine combinations of 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA)/2,2-bis[4-(4-aminophenoxy) phenyl] propane (BAPP) (Series A) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA)/bis[4-(3-aminophenoxy) phenyl] sulfone (BAPSM) (Series B) with three kinds of w-diamino-poly(dimethylsiloxane) with different number-average molecular weight added as a part of diamine. These polysiloxane-block-polyimides, having various compositions and chain lengths of the polysiloxane segments, were subjected to solution casting to prepare their films, and their surface and interface properties were analyzed by contact angle, XPS, AFM, and SEM. It was found that the surface tension and surface topography were greatly influenced by the composition and molecular weight of the polysiloxane segments because of their surface enrichment, which was affected by the environment and substrate with which the copolyimides had contacted. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2239–2251, 1997

Replication bypass and mutagenic effect of alpha-deoxyadenosine site-specifically incorporated into single-stranded vectors.

Abstract: alpha-2'-Deoxyadenosine (alpha) is a major adenine lesion produced by gamma-ray irradiation of DNA under anoxic conditions In this study, single-stranded recombinant M13 vectors containing alpha were constructed and transfected into Escherichia coli to assess lethal and mutagenic effects of this lesion The data for alpha were further compared with those obtained with M13 vectors containing normal A or a model abasic site (F) at the same site The transfection assay revealed that alpha constituted a moderate block to DNA replication The in vivo replication capacity to pass through alpha was approximately 20% relative to normal A, but 20-fold higher than that of F constituting an almost absolute replication block Similar data were obtained by in vitro replication of oligonucleotide templates containing alpha or F by Ecoli DNA polymerase I The mutagenic consequence of replicating M13 DNA containing alpha was analyzed by direct DNA sequencing of progeny phage Mutagenesis was totally targeted at the site of alpha introduced into the vector Mutation was exclusively a single nucleotide deletion and no base substitutions were detected The deletion frequency associated alpha was dependent on the 3'-nearest neighbor base: with the 3'-nearest neighbor base T mutation (deletion) frequency was 26%, whereas 1% with the 3'-nearest neighbor base G A possible mechanism of the single nucleotide deletion associated with alpha is discussed on the basis of the misinsertion-strand slippage model

A New Formation Process of Poly(phenylsilsesquioxane) in the Hydrolytic Polycondensation of Trichlorophenylsilane. Isolation of Low Molecular Weight Hydrolysates to Form High Molecular Weight Polymers at Mild Reaction Conditions

Abstract: Trichlorophenylsilane (TCP) was hydrolyzed in an toluene/water heterogeneous solvent system, and a low molecular weight hydrolysate with simple structure was isolated from the aqueous solution while a high molecular weight hydrolysate with complicated structure was isolated from the toluene layer. When this hydrolysis was conducted strictly at 0°C, the primary hydrolysate consisting mainly of phenylsilanetriol (PST) could be crystallized out from the aqueous layer. When the low molecular weight hydrolysate obtained from the aqueous layer was subjected to the KOH-catalyzed polycondensation in refluxing toluene, poly(phenylsilsesquioxane) (PPQS) with a highly ordered ladder structure could be obtained. Its molecular weight increased with decreasing molecular weight of the initial hydrolysate, and its silanol content oppositely decreased with it. Since this polycondensation proceeded stepwise, it has been considered that intramolecular cyclization is favored in the first condensation of the low molecular weight hydrolysate and that the resultant higher oligomers are then connected into high polymer with ladder structure by the silanol coupling. The molecular weight of PPQS finally obtained reached 120 kDa.

Copolymerization of γ-butyrolactone and β-butyrolactone

Abstract: The copolymerization of a 4-membered β-butyrolactone (βBL) and a thermodynamically stable 5-membered γ-butyrolactone (γBL) proceeds in the bulk state with BF 3 .OEt 2 as a catalyst at room temperature to give poly[(3-hydroxybutyrate)-co-(4-hydroxybutyrate)] (P(3HB-co-4HB)) whose structure is identical with that of a polyester formed by microorganisms. The copolymer structure was confirmed by 1 H and 13 C NMR spectroscopy. The monomer reactivity ratios were r (γBL) = 0.48 and r (βBL) = 0.58, respectively, and the unit composition of 4HB increases to 56% at high γBL to βBL ratio in the feed. End group analysis of the copolymer suggests the presence of a hydroxyl group and a carboxyl group at the ends of each polymer molecule. It was postulated that the monomers activated by BF 3 react with the hydroxy group derived from the water contaminant in the monomers.

Lap Shear Bond Strength of Thermoplastic Polyimides and Copolyimides

Abstract: Adhesion properties of various thermoplastic polyimides and copolyimides were studied in order to develop suitable heat resistant adhesive film with excellent hot-melt processability under moderate...

Novel Isomerization Polymerization of Glycidyl Acetate To Produce a Poly(ortho ester)

Abstract: A new mode of polymerization of glycidyl acetate (1a) to yield a poly(ortho ester), i.e., poly[(2-methyl-1,3-dioxolane-4,2-diyl)oxymethylene] (3a), was explored. This new polymerization exclusively proceeded when a bulky Lewis acid, methylaluminium bis(2,6-di-tert-butyl-4-methylphenoxide) (2a), was employed as the catalyst. The polymerization of 1a with 4 mol % of 2a proceeded smoothly in toluene at 0 °C and gave 3a in 82% after 1 h. The time-trace of the polymerization system revealed that this polymerization was completed within 3 min under these conditions. The polymerization mechanism is tentatively assumed as polyaddition of zwitterionic species produced from 1a with the assistance of 2a. The polymerization of glycidyl methacrylate (1b) with 2a gave poly(ortho ester) 3b in a similar manner.

A facile antistatic modification of polyester fiber based on ion-exchange reaction of sulfonate-modified polyester and various cationic surfactants

Abstract: A new technique for imparting antistatic properties to poly(ethylene terephthalate) (PET) fiber has been developed. In this technique, blend polyester fibers containing poly(ethylene terephthalate/5-sulfoisophthalate) (SIP-PET) were prepared by blend spinning and then treated with various cationic surfactants in the process of dyeing. The surfactants could effectively be immobilized on the fiber as the counter cations of the sulfonate groups of the 5-sulfoisophthalate (SIP) units and aid the release of static electrons formed in the fiber. Thus, the half-life time (t1/2) of leakage of static charge and the surface resistivity (Rs) of the blend PET fibers became much lower after treating. The best result was obtained with a methylated quaternary ammonium salt of a stearylamine-ethylene oxide (EO) adduct or hydrochloride of a laurylamine-EO adduct as the surfactant of which the number of EO units was around ten. Even after five washing cycles the t1/2 value of the fibers treated with these surfactants was kept lower than 30 s with the Rs value maintained in the order of 1013 Ω cm-2. Therefore, the present technique could be useful for practical production of polyester fibers with “semi-permanent” antistatic properties which can be recovered by re-treatment even if they were lost. Eine neue Methode zur antistatischen Ausrustung von Polyethylenterephthalat-(PET)-Fasern wurde entwickelt. Hierbei werden durch Blend-Spinnen hergestellte Polyesterfasern aus PET und Poly(ethylenterephthalat/5-sulfoisophthalat) wahrend des Ftirbens mit verschiedenen kationischen oberflachenaktiven Substanzen behandelt. Diese oberflachenaktiven Substanzen werden als Gegenionen zu den 5-Sulfoisophthalat-Gruppen auf der Faser immobilisiert und unterstutzen die Freisetzung statischer Elektronen in der Faser. Dadurch sinken die Halbwertszeit (t112) des Ab- baus statischer Aufladung und der Oberfachenwiderstand (Rs) der Blend-Fasern. Die besten Ergebnisse wurden mit einem methylierten quaternaren Ammoniumsalz eines Stearylamin-Ethylenoxid(E0)-Adduktes und dem Hydrochlorid eines Lauryl- amin-EO-Adduktes mit jeweils etwa zehn EO-Einheiten als oberflachenaktiver Sub- stanz erhalten. Auch nach funf Waschzyklen lag die Halbwertszeit t1/2, unter 30 s bei einem Rs-Wert in der Grosenordnung von 1013 Ω cm−2. Mit dieser Technik lieBen sich demnach Polyesterfasem mit “semi-permanenten” antistatischen Eigenschaften produzieren, die durch entsprechende Nachbehandlung, auch nach vollstandigem Verlust, wiederhergestellt werden konnten.

Studies on Functionalization of Polymers by Reactive Processing. Part 5. Prepartion of Polythiourea-immobilized Active Charcoal and Its Utilization for Selective Adsorption of Mercury (II) Ion.

Abstract: ポリアミンと二硫化炭素の反応をやし殻活性炭の存在下,水分散中で行い,ポリチオ尿素化合物を得た.両出発物質が活性炭にまず吸着されてから反応が進行し,ポリチオ尿素が活性炭上に強固に固定化されることを見いだした.得られた固定化ポリチオ尿素は優れた水銀イオン吸着能を有することを認めた.水銀吸着能はポリアミンの分子量が1800,活性炭への固定化率が11.8%のとき最もよく,それ以上固定化すると急激に減少することがわかった.固定化率と比表面積は逆の相関性があるが,この固定化率を越えると比表面積が急激に減少した.固定化ポリチオ尿素をカラムに詰めて10ppmの水銀水溶液を固定化物の5倍容量/時間で連続通液すると,10時間で法定基準値5ppbを越えた.このときの水銀吸着量は0,6molL-1(固定化物)であり,優れた水銀吸着能を有することが確認された.

A novel spin-finishing method for antistatic modification of polyester fiber. Surface reaction onto amine-containing copoly(amide-ethers) blended with polyester fiber

Abstract: Copoly(amide-ethers) containing two types of tertiary amine units were made as antistatic modifiers for poly(ethylene terephthalate) (PET) fibers. The filaments of the copolymers were melt-spun and reacted with three alkylating agents in order to quaternize the tertiary amine into a sulfo-betaine, a carbobetaine, and an ammonium ion. The apparent electric resistivity of the filaments was greatly reduced by this reaction, being in the range of 106 to 108 Ω/cm. However, because these quaternized copolymers incurred decomposition during blend spinning with PET, a blend PET fiber containing one type of copoly(amide-ether) was melt-spun and subjected to quaternization of the amino groups as well as to surface crosslinking with various alkylating and epoxy agents. The quaternized blend fibers obtained showed improved antistatic properties compared with the original blend fiber. Particularly, the fibers crosslinked with epoxy compounds were found to have the best antistatic properties that had ever been attained with this type of modification. The antistatic properties were retained even after dyeing, because both hydrophilic and ionic groups had been effectively immobilized on the surface. Since this quaternization and crosslinking could be conducted on-line with spinning and drawing within a short reaction time, this modification technique is called “spin-finishing method”, which should be superior to the conventional methods in terms of cost performance and productivity. Copoly (amid-ether) rnit zwei unteschiedlichen Aminfunktionalitaten wurden als antistatische Modifikatoren fur Polyethylenterephthalatfasern (PET) eingesetzt. Die tertiaren Aminogruppen schmelzegesponnener Copolymerfilamente wurden rnit drei Alkylierungsmitteln umgesetzt, wobei ein Sulfobetain, ein Carbobetain bzw. Ammoniumionen gebildet wurden. Dadurch wurde der scheinbare spezifische Widerstand der Filamente auf grosfienordnungsmasfiig 106 bis 108 Ω/cm verringert. Da sich die quaternisierten Copolymeren beim Blend-Spinnen rnit PET zersetzen, wurden Blendfasern von PET mit einem Copolymeren nach dem Schmelzespinnen einer Quaternisierung oder Vernetzung rnit Alkylierungsmitteln bzw. Epoxyvernetzern unterzogen, was die antistatischen Eigenschaften der Fasern im Vergleich rnit der unbehandelten Faser verbesserte. Insbesondere die mit Epoxiden vernetzten Fasern wiesen antistatische Eigenschaften auf, wie sie mit dieser Modifizierungsmethode bislang nicht erreicht wurden. Die antistatischen Eigenschaften blieben nach dem Fkben erhalten, da sowohl die hydrophilen als auch die ionischen Gruppen auf der Faseroberflache immobilisiert waren. Da Quaternisierung bzw. Vernetzung in einem Arbeitsgang rnit dem Verspinnen und Verstrecken der Fasern innerhalb einer kurzen Reaktionszeit erfolgen, sollte diese ”spin-finishing„ genannte Methode konventio- nellen Verfahren bezuglich Kosten und Produktivitat uberlegen sein.

Cationic ring-opening polymerization of (S)-2-ethoxy-4-isopropyl-5(4H)-oxazolone to yield poly(N-ethoxycarbonyl-L-valine)

Abstract: A new polypeptide derivative, poly(N-ethoxycarbonyl-L-valine) (2) was prepared for the first time by the cationic ring-opening polymerization of (S)-2-ethoxy-4-isopropyl-5(4H)-oxazolone (1). The polymerization proceeded with a cationic initiator, methyl trifluoromethanesulfonate, BF 3 OEt 2 , or trifluoromethanesulfonic acid, in an aprotic non-nucleophilic solvent such as toluene, chloroform, or nitromethane. The molecular weight of the resulting 2 was independent of the feed ratio of monomer to initiator but depended on the polymerization temperature. The number average molecular weight of 2 prepared at -40 °C was 11 000. The resulting polymer 2 showed high solubility in organic solvents, especially in halogenated hydrocarbons.

Cationic Ring-Opening Polymerization of 4,5-Dihydro-1,3-oxazol-5-ones to Produce N-Alkoxycarbonylated Polypeptides and Its Related Oligomerization

Abstract: The present paper describes the cationic ring-opening polymerization of 2-alkoxy-4,5-dihydro-1,3-oxazol-5-ones derived from L-valine, (L-isoleucine, L-leucine with methyl trifluoromethanesulfonate (MeOTf) as the initiator. The polymerization of these oxazolones proceeded successfully below 0°C and gave poly(N-alkoxycarbonyl-α-amino acid)s in moderate yields. The ease of polymerization was dependent on the 2- and 4-substituents of the oxazolone ring and the combination of bulky groups strongly reduces it. The reaction of 2-ethoxy-4,4-dimethyl-4,5-dihydro-1,3-oxazol-5-one with a catalytic amount of MeOTf did not produce a polymer, but yielded a bicyclic dimer, selectively.

Isolation and cationic ring-opening polymerization of 2,3,5,6-tetrahydroimidazo[2,1-b][1,3]oxazole to produce a thermally stable polyurea

Abstract: A bicyclic pseudourea, 2,3,5,6-tetrahydroimidazo[2,1-b][1,3]oxazole (1), was isolated for the first time, and its cationic and spontaneous polymerizations were examined. Both polymerizations gave poly(1,3-imidazolidin-2-one-1,3-diylethylene) (2) in high yields. The polymer is a crystalline solid with glass transition and melting temperature of 51°C and 286°C, respectively. Thermogravimetry showed that it is stable up to 450°C under nitrogen.