Yasuo Saegusa

Bromination of cellulose with tribromoimidazole, triphenylphosphine and imidazole under homogeneous conditions in LiBr-dimethylacetamide

Abstract The bromination of microcrystalline cellulose with tribromoimidazole, triphenylphosphine and imidazole was studied under homogeneous conditions in LiBr- N,N -dimethylacetamide. Bromodeoxycellulose samples having ds values up to 1.6 were obtained at high molecular ratios of bromination reagents to the repeating unit of cellulose (5 or higher). Recoveries of high ds samples were below 50%. 3,6-Dibromo-3,6-dideoxyglucose units were present in the samples having high ds values together with 3,6-dibromo-3,6-dideoxyallose and 6-bromo-6-deoxyglucose units. The dibromoglucose units were formed from dibromoallose units by a nucleophilic substitution of bromine atoms at C-3 with bromide ions present in the system.

Thermal analysis of epoxy curing using polyfunctional active esters as curing agents

Abstract The curing behavior of bisphenol A diglycidyl ether (BADGE) has been studied by differential scanning calorimetry and IR spectroscopy using active esters, the trifunctional compound 1,3,5-triacetoxybenzene (TAB) and tetrafunctional tetraphenoxycarbonyl pentaerythritol (TPCP) as curing agents, with which no free hydroxyl groups are left in the cured resins. The effects of the ratio of ester groups to epoxide groups ( r ) in the reaction mixture on the glass transition temperature ( T g ) and the thermal stability of the cured resins were also examined by thermomechanical analysis and thermogravimetry respectively. The T g has the maximum value of 72°C at r = 1 for either TAB or TPCP as curing agent. The thermal stability increases with increasing value of r .

Reaction of 6-bromo-6-deoxycellulose with thiols in lithium bromide-N, N-dimethylacetamide

Nucleophilic substitution reactions of 6-bromo-6-deoxycelluloses of high degrees of substitution with eight thiols having functional groups such as carboxyl and amino groups were studied under homogeneous conditions in LiBr-N, N-dimethylacetamide in the presence of triethylamine. The reactions under the homogeneous conditions proceeded more extensively than those run under heterogeneous conditions in aqueous alkaline solutions. The reactivity of thiols was found to increase with increasing acidity of the mercapto groups of the thiols. Reaction products with 2-mercaptobutanedioic acid and with 2-mercaptobenzoic acid were soluble in alkaline and neutral water but not in 1 N HCl, while the reaction products with 2-aminoethanethiol did not dissolve even in 1 N HCl. The reaction products with cysteine showed amphoteric behavior.

Reaction of dichloroallose units in a chlorodeoxycellulose with lithium chloride under homogeneous conditions in N,N-dimethylacetamide

Abstract The reaction of methyl 3,6-dichloro-3,6-dideoxy-β- d -allopyranoside with lithium chloride in N , N -dimethylacetamide (DMA) was studied in relation to the possible conversion of 3,6-dichloro-3,6-dideoxy- d -allose units in a chlorodeoxycellulose during synthesis in a LiCl-DMA solvent system. Methyl 3,6-dichloro-3,6-dideoxy-β- d -glucoside was formed; the reaction was reversible and the equilibrium was on the glucoside side. GLC analysis of the hydrolyzates of chlorodeoxycellulose samples after treatment with LiCl showed that the dichloroallose units were partly converted into 3,6-dichloro-3,6-dideoxy- d -glucose units. A kinetic study showed that the rate of conversion of the dichloroallose unit into the dichloroglucose unit was lower than that of the dichloroalloside into the dichloroglucoside, and the amounts of the two units at equilibrium were calculated to be close to each other. Based on the values of the kinetic parameters obtained, the conversion of the dichloroallose units into the dichloroglucose units during the chlorination of cellulose in LiCl-DMA was estimated to be negligibly small under typical reaction conditions.

Preparation and characterization of fluorine-containing aromatic condensation polymers. VI. Aromatic polybenzothiazoles from 4,4′-(hexafluoroisopropylidene)dibenzoic acid and tetrafluoroterephthalic acid and 2,5-diamino-1,4-benzenedithiol dihydrochloride

Two fluorine-containing aromatic polybenzothiazoles were synthesized by direct polycondensation of 4,4′-(hexafluoroisopropylidene)dibenzoic acid and tetrafluoroterephthalic acid with 2,5-diamino-1,4-benzenedithiol dihydrochloride using phosphorus pentoxide/methanesulfonic acid or polyphosphoric acid as both condensing agent and solvent. The effect of introduction of fluorine atom on the synthesis and properties of these polymers was discussed in detail. The perfluoroisopropylidene unit-containing polybenzothiazole was amorphous, and showed good solubility in organic solvents, excellent mechanical properties, and high thermal stability. The perfluoro-p-phenylene unit-containing polybenzothiazole was crystalline, and exhibited lyotropic behavior in concentrated sulfuric acid.

Anionic ring-opening polymerization of 2-phenyl-1,3,4-oxadiazolin-5-one and conversion of the resulting polymer, N-benzamido-1-nylon, to N-amino-1-nylon

SummaryThe ring-opening polymerization of 2-phenyl-1,3,4-oxadiazolin-5-one (1) was carried out anionically both in bulk and in DMF solution at 140°C for 15 h in the presence of various initiators, such as alkaline metal salts of 1, alkaline metal fluorides and tertiary amines, leading to N-benzamido-l-nylon (2) having Mns up to 2,000. Hydrolysis of the pendant benzamido groups of the resulting polymer was successfully achieved in aqueous ethanol containing concentrated hydrochloric acid at 100°C to give N-amino-l-nylon (3). The original polymer dissolves easily in aliphatic and aromatic alcohols and polar aprotic solvents, whereas the hydrolyzed polymer is not soluble in these solvents but highly soluble in water. In dilute aqueous solutions, the latter polymer behaves as common polyelectrolytes with flexible backbone. Polymers 2 and 3 began to lose weight in air at around 200 and 170°C, respectively.

Thermal behavior of poly(p-phenylene diacrylic acid diethyl ester)

Abstract Poly( p -phenylene diacrylic acid diethyl ester) was prepared by photopolymerization of p -phenylene diacrylic acid diethyl ester in the solid state. The resulting product was fractionated according to molecular weight by solvent extraction, and the effect of the molecular weight on the thermal behavior such as crystal-crystal transition, melting and thermal degradation was studied. The effects of reaction temperature and heat treatment on the thermal behavior of the polymer were also examined.

Synthesis of methyl 3,6-dibromo-3,6-dideoxy-β-d-allopyranoside and -glucopyranoside, and their interconversion in the presence of bromide ion

Abstract The bromination of methyl β- d -glucopyranoside with tribromoimidazole and triphenylphosphine in toluene-acetonitrile (2:1 v/v) for 4 h at 110°C gave methyl 3,6-dibromo-3,6-dideoxy-β- d -alloside in low yield, while the bromination in toluene under otherwise comparable conditions gave methyl 3,6-dibromo-3,6-dideoxy-β- d -glucoside. Examination of the time course of the reaction in toluene showed that the dibromoalloside was initially formed and was converted into the dibromoglucoside during the bromination. The rate constants of the interconversion between the dibromoglycosides in LiBr- N , N -dimethylacetamide (DMA) were about 10 3 times as large as those of the interconversion of the corresponding dichloroglycosides in LiCl-DMA. The results are discussed in relation to the presence of 3,6-dibromo-3,6-dideoxyglucose residues, in addition to 3,6-dibromo-3,6-dideoxyallose and 6-bromo-6-deoxyglucose residues, in bromodeoxycellulose samples having high ds values obtained by the bromination of cellulose with tribromoimidazoletriphenylphosphine.