Properties of the liquid cis-1, 4-polyisoprene with molecular weight of tens of thousands were studied. This liquid polyisoprene is more flexible and has lower viscosity and lower temperature dependence of viscosity, than other liquid polymers of similar molecular weights such as polyisobutylene and polybutene. It plasticized the rubbers efficiently and works as a very useful plasticizer for solution type and hot melt type adhesive tapes and adhesives. Moreover, it could be vulcanized by conventional crosslinking techniques such as curing with sulfur to provide elastomeric materials with practical mechanical properties. It worked as an excellent plasticizer for various solid rubbers in the unvulcanized state and was covulcanized with rubber by curing. Its use as a curable plasticizer is quite useful for getting a variety of rubber compounds with good processibilities and physical properties and for plasticizing rubbers for which oil is undesirable to use as a plasticizer because of the bleeding.

View full abstract

Acrylic acid was polymerized to polyester, _??_CH₂CH₂COO_??__n, using potassium or sodium salt of carboxylic acid as an initiator in the presence of 18-crown-6 at 80°C. The crown ether was found to accelerate the carboxylate-initiated reaction, and the product of high degree of polymerization was formed. It was confirmed by NMR and IR spectroscopies that the product had the same polyester structure as poly (β-propiolactone). The average degree of polymerization increased with increasing reaction time at a higher rate in the presence of the crown ether. These findings suggested that the polyester was formed by nucleophilic addition of the acrylate or the polymeric carboxylate anion to the carbon-carbon double bond of acrylic acid to give a carbanion followed by the proton abstraction from the carboxyl group by the carbanion. The crown ether plays an important role in the activation of the carboxylate anion by complexing with potassium or sodium cation.

View full abstract

Thermodynamic behavior was studied on the cationic polymerization of 1, 3, 6, 9, 12, 15-hexaoxacyclof-heptadecane (17-CF-6) with boron trifluoride etherate by determining the equilibrium concentration of cyclic oligomers in dichloromethane. The entropy changes in polymerization ΔS_p⁰ were -2.12±1.60, 9.0, 10.7, 12.1, and 13.1 cal/K·mol for monomer, dimer, trimer, tetramer, and pentamer, respectively. The enthalpy changes ΔH_p were 2.58±0.43 kcal/mol for monomer and 0 for the oligomers. The result indicates that the polymerizability of the monomer is controlled by ΔH_p term, and that of cyclic oligomers by ΔS_p⁰ term. The molar cyclization equilibrium constant decreases in proportion to the -2.5 power of the ring size x which is equal to or larger than 3 in accordance with the Jacobson-Stockmayer theory.

View full abstract

The mechanism of the oligomerization of 2H_-azirines and of the decomposition of the oligomers to form dihydropyrazines was investigated by examining the effects of additives and solvents on the rate of the oligomerization. The oligomerization in alcoholic solvents is initiated by aminoacetal, which is formed by addition of two moles of alcohol to the azirine, and by t-butylamine. Both initiation and propagation proceed by two-step reactions, which consist of attack of amino group to the imino linkage of azirine to form aminoaziridine in the 1st step and ring opening in the 2nd step. Decomposition of the oligomer to dihydropyrazine was catalyzed by small amount of water and was proved to proceed via hydrolysis of the imino linkage and intra- and intermolecular condensation between the resulting amino and formyl groups.

View full abstract

Seven kinds of model oligomers of isomeric polyphenylene phthalamide (PPPA) containing meta-and/or para-substituted, benzene rings in the main chain were synthesized. The infrared absorptions specific for meta- and para-substituted benzene rings were observed at 780 cm^-1 and 820 cm^-1, respectively. A calibration curve was presented to determine the isomer composition of isomeric PPPA. The thermal stability of these oligomers was investigated by thermogravimetry and differential scanning calorimetry. The initiation of degradation was observed at temperatures in the neighborhood of the melting points (≥665 K) of the oligomers. It was found that the fusion entropy increased with an increase in number of meta-substituted benzene rings.

View full abstract

The polymerization of 1, 3-butadiene in cycloalkanone with hydrogen peroxide was investigated. The polymers obtained have carboxyl and hydroxyl groups by 1 to 1 ratio. The molecular weight of polymers was controlled by the amounts of hydrogen peroxide and cyclohexanone. In this polymerization, besides the polymer, 1, 12_-dodecanedioic-acid, small amounts of oxycaproic acid, and caproic acid were also detected. Accordingly, the main primary radicals are supposed to be caproic carbo radical and hydroxyl radical. The ¹H NMR investigation of the polymer suggested the presence of hydroxyl group at the end of the polymer. The interaction of hydrogen peroxide with cyclohexanone gave several forms of ketone peroxides in the polymerization process (in situ). These peroxides decomposed into hydroxyl radical and hydroxycyclohexyloxy radical, and then the latter radical gave caproic carbo radical by β-scission. All these radicals initiate the polymerization. Cyclopentanone-hydrogen peroxide also initiated the same reaction and gave the terminal functionated liquid polybutadiene. From the results of the thin layer chromatography (TLC) of the polymer, it was found that the liquid polybutadiene has at least one functional group.

View full abstract

The polymerization of 1, 3-butadiene with cyclohexanone peroxides was investigated. The terminal functional groups of the polymers prepared under various conditions were compared with those of the standard polymer obtained by cyclohexanone-hydrogen peroxide. 1-Aminocyclohexyl hydroperoxide (AHP) and tricyclohexylidenetriperoxide (TCTP) were synthesized from cyclohexanone, hydrogen peroxide, and other additives. Then, 1, 3-butadiene was polymerized in the presence of these peroxides. When tertiary amine having alkyl chains of intermediate length e. g., tri-n-butyl amine, was added, the carboxyl content of the polymer increased. The amine would attack ketone peroxide nucleophilically to form caproyl radicals which initiate the polymerization. The polymerization initiated by AHP and the polymerization in the presence of ammonia afforded polymers having carbamoyl groups in addition to the carboxyl group at the chain end. The carbamoyl groups were converted to carboxyl groups by hydrolysis. The polymers obtained by TCTP have a small amount of hydroxyl terminals together with alkyl terminals. It was concluded that cyclohexanone reacts with hydrogen peroxide to form cyclohexanone peroxides, which decompose to radical initiators of the polymerization.

View full abstract

An oligobiphenylene with diazo-thio ether bonds (I) was obtained by the reaction of biphenyl1-4, 4′-bis (diazonium chloride) and 4, 4′-dimercaptobiphenylene in aqueous acetone solution at temperature below 5°C. Oligomers with 3, 3′-dimethyl and dichloro substituents (II and III, respectively) were also prepared by the similar method. Oligomer II was soluble in common organic solvents, and its M_n measured by a vapour pressure osmometer in benzene solution was about 5000. Oligomers I and III were hardly soluble except in N, N-dimethylformamide and N-methyl-2-pyrrolidone (NMP). Oligomer I in NMP solution decomposed at above 70°C with evolution of nitrogen gas to give poly (4, 4′-biphenylene sulfide). It initiated the radical polymerization of vinyl monomers. Futhermore, when a nearly equimolar mixture of acrylonitrile and oligomer I was heated at 70°C, a copolymer having acrylonitrile unit, biphenyl and sulfur in the main chain was obtained. Decomposition temperatures of these oligomers differed by substituents, but they showed nearly the same reactivities.

View full abstract

Curing properties of various oligoester acrylates (OEA) and their mixtures were studied by means of IR spectroscopy to obtain the formulation for curing the oligomers by UV irradiation in air into films at high speed and in high conversion. Good films were obtained from the combination of a monofunctional OEA, which can easily be cured almost quantitatively in a comparatively short time, and a polyfunctional OEA, which has a high curing rate in the initial stage, by mixing both the OEA's in such a ratio as to make the glass transition temperature of the cured film below about 60°C. Compared with methacrylate oligomers, acrylate oligomers having the same residual structure as the former were cured more than 10 times faster. Molecular oxygen inhibited the curing due to the reaction with the structural residue of main chain rather than the reaction with the polymerizable functional group. Polyfunctional OEA containing tetrahydrophthalate residue was recognized to exhibit good curing properties in air.

View full abstract

Cationic oligomerization reactions of p-isopropenylphenol (IPP) was studied at various temperatures using conventional metal halides as initiators. It was found that the reaction products and their structures were very different depending on the reaction temperatures. Thus, in the reaction at 75°C, saturated cyclic dimmer (60%) and saturated trimer (40%) produced by the addition of IPP to the cyclic dimer were obtained. At 25°C, cis- and trans-isomers of unsaturated linear trimer (87%), two kinds of unsaturated linear dimers (10%), and a small amount of higher oligomers were obtained. At 0°C and -20°C, the oligomers obtained had average molecular weights of 620-710 and 1200-2300, respectively. The structures of these products were determined using GPC, IR, UV, ¹H- and ¹⁸C-NMR measurements.

View full abstract

Diacrylates were prepared by the addition reaction between epoxy resins of bisphenol type and acrylic acid in the presence of polyfunctional acrylates such as ethylene glycol diacrylate. The reaction did not proceed readily at 110-120°C in the absence of catalyst and the reaction at 120°C for 12 h caused gelation, while it proceeded readily at the same temperature in the presence of catalyst such as sodium benzoate or quaternary ammonium salt. Hydroquinone monoethyl ether worked as an inhibitor for a side reaction, i. e., thermal polymerization of acrylates when the reaction was carried out in air, but gelation occurred due to the thermal polymerization in nitrogen atmosphere.

View full abstract