Yasuo Yuki

Triazine dendrimers by divergent and convergent methods

Two types of dendrimers with a 1,3,5-triazine ring at the branch point were synthesized by divergent and convergent methods. The divergent method began with 2,4,6-tris(p-nitroanilino)-1,3,5-triazine as a trifunctional core. Each cycle involved the reduction of the peripheral NO2 group followed by a reaction with 2-chloro-4,6-bis(p-nitroanilino)-1,3,5-triazine. The synthetic cycle was completed by the coupling with 2,4-dianilino-6-chloro-1,3,5-triazine (DACT) to eventually accomplish second-generation dendrimers ([G2]3-C) bearing 12 benzene rings at their edge. The convergent approach started with the reaction of DACT with p-nitrophenol to give rise to 2,4-dianilino-6-(p-nitrophenoxy)-1,3,5-triazine. The synthetic cycle consisted of reduction of the NO2 group and coupling with 2,4-dichloro-6-(p-nitrophenoxy)-1,3,5-triazine. The final step was the connection of each monodendron with cyanuric chloride to produce tridendron; in this way, the second-generation dendrimer ([EG2]3-C) was obtained. Gel permeation chromatography analyses indicated the aggregation of dendrimers in solution. Ultraviolet spectroscopic analyses revealed that the larger dendrimer had a more conjugated electron system from the core to the periphery. The thermal properties were evaluated by thermogravimetric analysis (TGA); excellent heat resistance was indicated, especially in [G1]3-C, which included alternately imine-like nitrogen-linked 1,3,5-triazine and benzene rings.

Living Radical Polymerization of Styrene with Diphenyl Diselenide as a Photoiniferter. Synthesis of Polystyrene with Carbon-Carbon Double Bonds at Both Chain Ends

Abstract Photopolymerization of styrene in the presence of diphenyl diselenide proceeded smoothly. The polymer yields and the number average molecular weight (Mn) of the polymers increased with reaction time. Further, a linear relationship was found for a plot of Mn for polystyrene versus polymer yield. These results indicate that this polymerization proceeds through a living radical mechanism. Photopolymerization of styrene with bis(p-tertbutylphenyl) diselenide afforded a telechelic polystyrene with terminal arylseleno groups. The resulting polymer underwent the reductive elimination of terminal seleno groups by the reaction with tri-n-butyltin hydride. Moreover, this telechelic polymer was treated with hydrogen peroxide to afford polystyrene with carbon-carbon double bonds at both chain ends.

RADICAL POLYMERIZATION OF METHYL METHACRYLATE WITH DIPHENYL DISELENIDE UNDER THERMAL OR PHOTOIRRADIATIONAL CONDITIONS

Polymerization of methyl methacrylate (MMA) with diphenyl diselenide (DPDSE) in the presence of AIBN at 60°C was investigated. DPDSE was worked as a chain transfer agent (CTA). The chain transfer constant (Ctr) of DPDSE for MMA was estimated to be 1.43. On the other hand, DPDSE was functioned as a photoiniferter for the photopolymerization of MMA. In a limited range of conversion, both the polymer yield and number average of molecular weight ([Mbar]n) increased with the reaction time, and the [Mbar]n linearly increased with the yield. The terminal structure of poly(MMA) was investigated by the 77Se NMR spectrum based on Methyl α-phenylseleno isobutylate (MSEPI) as model compound of the ω-chain end of poly(MMA). Further, photopolymerization of poly (MMA) containing phenylseleno group at ω-chain end as a polymeric photoiniferter with MMA effectively afforded a poly (MMA) having higher molecular weight.

Synthesis of polystyrenes with arylseleno groups at the terminal bond, by the free radical polymerization of styrene in the presence of diaryl diselenides, and their conversion to end functional polymers

Abstract Free radical polymerization of styrene in the presence of diphenyl diselenide, initiated by 2,2′-azobisisobutyronitrile (AIBN) at 60°C, was investigated. Diphenyl diselenide worked as a chain transfer agent and its chain transfer constant was estimated to be 28.0, which is remarkably larger than that of the sulphur analogue, diphenyl disulphide. Polymerization with bis( p-tert -butylphenyl) diselenide gave a polystyrene containing a 1-cyano-1-methylethyl group at the α -end and an arylseleno group at the ω -end, respectively, and the degree of functionality was nearly 1.0. The arylseleno group at the ω -end was reduced quantitatively by the reaction with tri- n -butyltin hydride. This group was also eliminated by treatment with hydrogen peroxide, to give an end functional polystyrene with a carbon–carbon double bond at the ω -end. Further, this double bond was converted to an epoxy group by the oxidation with m -chloroperbenzoic acid.

Synthesis of star polystyrene by radical polymerization with 1,2,4,5-tetrakis(p-tert-butylphenyl selenomethyl)benzene as a novel photoiniferter

Abstract 1,2,4,5-Tetrakis(p-tert-butylphenylselenomethyl)benzene was synthesized and used as a tetrafunctional photoiniferter for the polymerization of styrene. Both the yield and the number average molecular weight ( M n ) of polymers increased with reaction time and M n linearly increased with yield of polymer. The polymerization of styrene using this novel photoiniferter permitted formation of star-shaped polystyrene containing arylseleno groups at the chain ends, and the average degree of functionality was 3.2. Photopolymerization of styrene with end-functional star polystyrene as polymeric photoiniferter afforded polystyrene having high molecular weight.

Synthesis of Telechelic Polystyrene by Radical Polymerization Using 1,4-Bis(p-tert-Butylphenylseleno-Methyl)benzene as a Photoiniferter

Abstract 1,4-Bis(p-tert-butylphenylselenomethyl) benzene was synthesized, and used as a bifunctional photoiniferter for the polymerization of styrene. Both the polymer yields and the number average of molecular weights (n) of polymers increased with the polymerization. The polymerization of styrene by this iniferter permitted telechelic polystyrene containing arylseleno groups at both chain ends, and the degree of functionality was 1.9. The seleno groups of both chain ends of polystyrene were reduced quantitatively by tri-n-butyltin hydride. These seleno groups in polystyrene were also eliminated by treatment with hydrogen peroxide to give telechelic polystyrene with carbon-carbon double bond at both chain ends. Further, polystyrene with double bonds was converted to telechelic polystyrene carrying terminal functional groups as epoxy, hydroxy, and iodide group, respectively. † Deceased August 5, 1997

Convenient Synthesis of Lactones by the Reaction of Diols with N-Haloamides

Abstract Reaction of 1,4-butanediol or 1,5-pentanediol with N-haloamides such as N-chlorosuccinimide, N-bromosuccinimide, N-bromoacetamide, isocyanuric chloride, and N,N-dichlorobenzene-sulfonamide under mild conditions gave γ -butyrolactone or δ-valerolactone, respectively, in high yields.

SYNTHESIS OF MACROMONOMER USING END FUNCTIONAL POLYSTYRENE PREPARED FROM p-METHOXYBENZYL p-TRIMETHYL-SILYLPHENYL SELENIDE AS A PHOTOINIFERTER

The end functional polystyrene having phenylseleno group at ω-chain end was prepared from radical polymerization of styrene in the presence of p-methoxybenzyl p-trimethylsilylphenyl selenide as a photoiniferter. The phenylseleno group at ω-chain end in polystyrene was eliminated by hydrogen peroxide. The resulting polystyrene was interconverted quantitatively to polystyrene having epoxy end group by the oxidation with m-chloroperbenzoic acid. The macromonomer having a meth-acryloyl end group was synthesized from polystyrene containing epoxy end group with methacrylic acid in xylene at 140°C. Copolymerization of this macromonomer with methyl methacrylate afforded effectively a graft copolymer composed of a poly-(methyl methacrylate) backbone and polystyrene branches.

Preparation and Free-Radical Polymerization of 2,4-Dichloro-6-(p-Vinylphenyl)-1,3,5-triazine as a Reactive Monomer Containing Two Replaceable Groups

Abstract A new monomer containing two replaceable groups, 2,4-dichloro-6-(p-vinylphenyl)-1,3,5-triazine (DCVT) was prepared by the reaction of p-vinylphenylmagnesium chloride with cyanuric chloride. This monomer was polymerized readily in benzene by AIBN at 60°C. From the copolymerization with styrene, Q and e values of DCVT were obtained as Q = 2.42 and e = 0.08. An insoluble terpolymer prepared from DCVT, styrene, and divinylbenzene was treated with several nucleophilic reagents, including sodium methoxide, sodium methylmercaptide, dimethylamine, and triethylphosphite, to afford the corresponding polymers in high conversions.

Synthesis and polymerization of isopropenyltriazines containing two alkyl groups and side-chain crystallization of the resulting polymers

Abstract 2,4-Bis( N -ethylanilino)-6-isopropenyl-1,3,5-triazine (BEIT) and 2,4-bis( N -octadecylanilino)-6-isopropenyl-1,3,5-triazine (BOIT) were prepared by the alkylation reaction of 2,4-dianilino-6-isopropenyl-1,3,5-triazine with the corresponding alkyl halides in the presence of sodium hydride in dimethylsulphoxide. The homopolymerization of these monomers and their copolymerization with styrene or methyl methacrylate were carried out using azobisisobutyronitrile as the initiator in benzene. The monomer reactivity ratios ( r 1 and r 2 ) were determined for these monomers. The homopolymerization rate and the monomer reactivity in the copolymerization for BOIT were lower than those for BEIT. For the polymers from BOIT, exothermic crystallization peaks and endothermic melting peaks based on the side chains of the comb-like polymers were observed in differential scanning calorimetry thermograms. The crystallinity of the side chains decreased with increasing content of styrene or methyl methacrylate in the copolymers.