Yuji Minoura

Cyclocopolymerization of d-limonene with maleic anhydride

Abstract d -Limonene (Lim), a nonconjugated 1,5-diene, was copolymerized with maleic anhydride (MAn) in tetrahydrofuran with α,α′-azobisisobutyronitrile as initiator. The composition, spectral analyses, and other physical properties of the resulting copolymer and its hydrolysed product suggest that Lim readily undergoes an inter-intramolecular cyclocopolymerization with MAn, leading to a 1:2 alternating copolymer. The findings and the proposed cyclocopolymerization mechanism are consistent with participation of a charge-transfer complex of the comonomers in the propagation step. The copolymers are optically active and their CD spectra are characterized by dichroic bands attributable to electronic transitions of carbonyl or carboxylic chromophores.

Diimide reduction of cis-1,4-polyisoprene with p-toluenesulphonylhydrazide

Abstract The hydrogenation of cis-1,4-polyisoprene with diimide generated in situ from p-toluenesulphonylhydrazide (TSH), was investigated under various conditions. In aromatic solvents at 100–140°C, the rate of hydrogenation was increased with increase in concentration of polyisoprene and of TSH. Part of the polymer was depolymerized and cyclized during the reaction. Increasing the hydrogenation tended to decrease the rate of sulphur vulcanization, of the compounded rubber and the physical properties of vulcanizates were poor. The reaction of polyisoprene rubber with TSH, was also carried out in a solid state at 140°C for 20–60 min. It was found that by using a large amount of TSH hydrogenation and cyclization of rubber occurred. The quantity of TSH used as a blowing agent, for rubber in the manufacture of sponge rubber, i.e. 5–10 phr, did not cause hydrogenation.

Effect of hexamethylphosphorictriamide on the “living” radical polymerization initiated by aged Cr2+ BPO

The “living” radical polymerizations with aged Cr2++ benzoyl peroxide (BPO) are carried out in N,N′-dimethylformamide(DMF)+hexamethylphosphorictriamide(HMPA) mixed solvent. The initial rate of polymerization (Rp) in the mixed solvent is about three times that in DMF. The linear plots of conversion against time and the number average degree of polymerization (text-decoration:overlinePn) against conversion plots for the polymerization pass through the origin and for this reason the “living” polymerization can be treated quantitatively. It is found that the rate constants of the propagation step, calculated from the combination of Rp and text-decoration:overlinePn using certain assumptions, are very small compared with those for a conventional free radical polymerization.The rate of polymerization at 30°C or below decreases with time during prolonged polymerization. In contrast a steep increase in text-decoration:overlinePn is observed in the region of high monomer conversion. The molecular weight distribution curves of polymer obtained at 20°C have a single peak which shifts with conversion. However, these curves become bimodal at high conversion.On the other hand, typical dead-end polymerizations occur at high temperatures (50 and 60°C), i.e., the polymerization stops completely before reaching ≈ 10% conversion. text-decoration:overlinePn values of polymer obtained at a high temperature are relatively larger than those obtained at a low temperature and increase with the polymerization time even after the polymerization has stopped. These results are explained in terms of recombinations of growing polymer radicals, i.e., the complexed polymer radicals (P·--- CrIII) which are propagating species in the “living” polymerization dissociate to free radicals and CrIII.

Polymerization of vinyl monomers initiated by chromium(II) acetate + organic peroxides

The redox initiator systems consisting of chromium(II) acetate (Cr2+) and organic peroxides are studied in dimethylformamide (DMF) at low temperatures. The second-order rate constants of reduction of benzoyl peroxide (BPO) with Cr2+ are 0.65, 0.24 and 0.075 dm3 mol–1 min–1 at –10, –20 and –28°C, respectively.The activity of organic peroxides for the redox polymerization of methyl methacrylate (MMA) at –28°C decreases in the following order; hydroperoxide > diacylperoxide > perester = dialkyl peroxide.The kinetics of polymerization of MMA are different from that of a conventional free-radical polymerization. The dependence of the initial rate of polymerization (Rp) on the concentrations of initiator components, Cr2+ and BPO, is very small; the kinetic orders are 0.1 and 0.2, respectively. However, Rp is proportional to the square of the concentration of MMA. This result is explained in terms of a primary radical termination.The polymerization of MMA with the Cr2++ BPO system is found to occur continuously without a dead end polymerization after red Cr2+ changed to blue Cr3+, i.e., after Cr2+ was consumed by the redox reaction with BPO. The degree of polymerization of PMMA obtained by this initiator system below 30°C increases with an increase in monomer conversion.

“Living” radical polymerizations of vinyl monomers initiated by aged “Cr2++ BPO” in homogeneous solution

Monomer is added to chromium(II) acetate (Cr2+) and benzoyl peroxide (BPO) previously treated at 10°C in dimethylformamide (DMF)(the ageing process), and polymerizations are performed. It is found that the degree of polymerization of poly(methyl methacrylate)(PMMA) obtained at 30°C or below increases with an increase in monomer conversion and the single peak of a molecular weight distribution curve shifts with monomer conversion. These results suggest that a “living” polymerization occurs in the homogeneous polymerization of MMA initiated by the aged “Cr2++ BPO” system.The polymerizations of various vinyl monomers with this initiator system are carried out at 25°C. The polymerization activity is relatively high for MMA, acrylonitrile, methyl acrylate and acrylamide but low for styrene, vinyl acetate and vinyl chloride. The molecular weights of polyacrylonitrile and poly(methyl acrylate) also increase with the monomer conversion.By copolymerizing MMA with acrylonitrile, it is found that polymerizations with aged “Cr2++ BPO” proceed via a free radical intermediate. The polymerization rates (Rp) of MMA at 25 and 30°C are expressed by the following relation, Rp= const.[aged “Cr2++BPO”]0.7–1.0[MMA].The mechanism of a “living” radical polymerization is discussed in terms of a transition metal complex with free radicals.

Non-catalysed polymerization of acrylamide

Abstract It was found that acrylamide which had been left standing in air for several weeks polymerized spontaneously in water at room temperature at a rapid speed of polymerization in spite of the absence of an initiator. Poly(acrylamide peroxide) was found in acrylamide that had stood for a long time and in acrylamide that had been irradiated with daylight, while no peroxide was found in propion amide. These results seem to show that the above spontaneous polymerization was initiated by the peroxide which was formed in the acrylamide monomer. The formation of the peroxide was promoted by light and its decomposition was promoted by the addition of water. The polymerization of acrylamide was carried out by using the separated poly(acrylamide peroxide). The rate of polymerization increased with increase in the water content, but was slow in solvents containing other polar solvents such as halide solvents and alcohols. No polymer was obtained when a little picric acid was added. When acrylamide was polymerized in water with the peroxide, the rate of polymerization was found to be proportional to the monomer concentration and to the square root of the peroxide concentration. This peroxide also initiated the polymerization of methacrylic acid in water to produce a block copolymer.

Asymmetric radical polymerization of butadiene 1-carboxylic acid

Abstract Optically active S (−)- α -phenethylammonium butadiene 1-carboxylate was prepared and polymerized in methanol, using azobisisobutyronitrile as initiator. The optical rotation, optical rotatory dispersion and circular dichroism spectra of the polymers, before and after removal of chiral amine, have demonstrated that the asymmetric induction occurred in the main chain. An asymmetric inductive polymerization mechanism is discussed.

Polymerization of vinyl monomers by the reaction products of diphenyl sulphoxide with potassium

Abstract Diphenyl sulphoxide (DPSO) reacts with an equimolar amount of potassium (K) in tetrahydrofuran (THF) at −78° to form a reddish-black solution, giving an electron spin resonance (ESR) signal only below −70°. The signal is attributed to a very labile DPSO anion radical. The solution of DPSO-K (1/1) reaction products reacts further with another molecular amount of K at this temperature to give no ESR signal. The DPSO-K (1/1) reaction products initiates the polymerization of acrylonitrile (AN), but not the polymerizations of methyl methacrylate (MMA), styrene (St) or isoprene (IP). The active species of the solution initiating the polymerization of AN is assumed to be potassium benzene sulphenate from analyses of the solution and the infra-red spectrum of AN oligomers obtained using the complex. The DPSO-K (1/2) reaction products solution initiates the polymerization of MMA, St and IP as well as AN. The active species initiating the polymerization of MMA, St or IP is assumed to be phenylpotassium.

Asymmetric addition of thiol to diene polymer in the presence of optically active amines as catalyst

Abstract The asymmetric addition reaction of thiolacetic acid or benzylmercaptan to diene polymer (natural rubber, cis - and trans -1,4-polyisoprene, cis -1,4-polybutadiene, various styrenebutadiene copolymers and alternating acrylonitrile-butadiene copolymer) by optically active catalysts such as d -bornylamine ([α] d −45.2°), l -aspartic diethyl ester (−11.2°), l -aspartic dibutyl ester (−5.3°) were carried out in benzene at room temperature to 90°C. The optically active polymers were obtained from natural rubber and cis -1,4- and trans -1,4-polyisoprene, but were not obtained from cis -1,4-polybutadiene, styrene-butadiene copolymers, and butadiene-acrylonitrile copolymer. The [ α ] 25 D value of optically active derivatives was −0.1° ∼ −1.0° (in benzene), and the optical rotatory dispersion curves were found to fit the simple Drude equation.

Reaction of thiol to diene polymer in the presence of various catalysts

Abstract The addition reaction of benzylmercaptan to diene polymer (natural rubber, and cis -1,4-polyisoprene) by various optically active catalysts such as d -camphorsulphonic acid, d -percamphoric acid, and active-amylalcoholate (sodium and barium) were carried out in benzene or anisole at room temperature to 100°C. The optically active adduct polymer was only obtained from the reaction of benzylmercaptan to natural rubber and cis -1,4-polyisoprene by active-amylalcoholate (barium), but was not obtained by the other catalysts. The [ α ] 25 value of optically active adduct polymer was −0·1°C∼−0·6°C (in benzene), and the optical rotatory dispersion curves were found to fit the simple Drude equation. The reaction of benzylmercaptan to cis -1,4-polybutadiene, various styrene-butadiene copolymers, and alternating butadiene-acrylonitrile copolymer were carried out, but the optically active adduct polymers were not obtained by these catalysts.