Tetrahydrofuran, 2,5-divinyl

On each of the curves, the points at lowest X represent swelling in cyclohexane, the next in tetrahydrofuran and the last in benzene. In all cases, the samples were swollen in the pure solvent. The curves are reproduced from Figure 13 of Reference 19. The networks were made from anionically polymerized polyr-styrene using a bifunctional initiator crosslinked subsequently by divinyl benzene. The curves correspond to different ratios of divinyl benzene (DVB) per polystyrene living end (LE),... 

Some chemicals are susceptible to peroxide formation in the presence of air [10, 56]. Table 2.15 shows a list of structures that can form peroxides. The peroxide formation is normally a slow process. However, highly unstable peroxide products can be formed which can cause an explosion. Some of the chemicals whose structures are shown form explosive peroxides even without a significant concentration (e.g., isopropyl ether, divinyl acetylene, vinylidene chloride, potassium metal, sodium amide). Other substances form a hazardous peroxide on concentration, such as diethyl ether, tetrahydrofuran, and vinyl ethers, or on initiation of a polymerization (e.g., methyl acrylate and styrene) [66]. 

Thiourea dioxide (aminoiminomethanesulfinic acid) reduced diaryl ditellurium and divinyl ditellurium derivatives in tetrahydrofuran, to which an ammonium salt such as cetyltrimethylammonium chloride, serving as a phase-transfer catalyst, and 50% aqueous sodium hydroxide had been added4,5. 

Z,Z)-Divinyl Tellurium4 To a stirred suspension of 0.383 g (3 mmol) tellurium in 15 ml ethanol kept under nitrogen are added in small portions 0.34 g (9 mmol) of sodium borohydride. The mixture is heated and 0.32 g (8 mmol) sodium hydroxide, 15 m/ water and 5 ml tetrahydrofuran arc added. The mixture is refluxed until all the tellurium has disappeared. When the refluxing mixture has turned yellow (3 to 6 h), it is cooled to 20°, diluted with 50 m/ethyl acetate, and washed with three 30-m/portions of a saturated aqueous solution of ammonium chloride and then with three 30-m/-portions of brine. The organic phase is separated, dried with anhydrous magnesium sulfate, and filtered. The solvent is evaporated from the filtrate on a rotary evaporator at 20 torr. The residue is flash-chromatographcd on silica gel with mixtures of hexane and ethyl acetate. 

Organo Vinyl Tellurium (from Vinyl Tellurium Iodides) A solution of the vinyl tellurium iodide, prepared by addition of 0.25 g (1.0 mmol) iodine in benzene to the divinyl ditelluride (1.0 mmol) in 5 ml tetrahydrofuran at 0° under nitrogen, is added dropwise to a solution of the organo magnesium bromide in 10 m/ tetrahydrofuran at 0°. The mixture is stirred at 20° for 1 h, hydrolyzed with a saturated aqueous solution of ammonium chloride, extracted with diethyl ether, the extract dried with magnesium sulfate and evaporated. The product is chromatographed on silica gel with petroleum ether (30-60°)/ethyl acetate (9 1) as eluent. The following compounds were prepared in this manner (yields in parentheses are for the reactions with vinyl tellurium iodides) ... 

Diethyl ether Diisopropyl ether Divinyl ether Other aliphatic ethers Tetrahydrofuran... 

Smeets and co-workers reported the synthesis of amphiphilic HBP from the copolymerisation of a vinyl and divinyl monomers [11]. Grafting of HBP has also been reported by other researchers [12]. Hou and Yan reported the synthesis of a star-shaped copolymer using in situ grafting, which contained a hyperbranched poly(3-methyl-3-oxetanemethanol) core and tetrahydrofuran arms [13]. 

More recently, iodonium salts have been widely used as photoinitiators in the polymerization studies of various monomeric precursors, such as copolymerization of butyl vinyl ether and methyl methacrylate by combination of radical and radical promoted cationic mechanisms [22], thermal and photopolymerization of divinyl ethers [23], photopolymerization of vinyl ether networks using an iodonium initiator [24,25], dual photo- and thermally-initiated cationic polymerization of epoxy monomers [26], preparation and properties of elastomers based on a cycloaliphatic diepoxide and poly(tetrahydrofuran) [27], photoinduced crosslinking of divinyl ethers [28], cationic photopolymerization of l,2-epoxy-6-(9-carbazolyl)-4-oxahexane [29], preparation of interpenetrating polymer network hydrogels based on 2-hydroxyethyl methacrylate and N-vinyl-2-pyrrolidone [30], photopolymerization of unsaturated cyclic ethers [31] and many other works. 

Petro and co-workers [31] used a moulded monolithic rod of macro porous PS-divinyl benzene copolymer as a separation medium for the HPLC of styrene oligomers and copolymers, e.g., styrene-2-naphthyl-methacrylate. On column precipitation redissolution chromatography is an alternative to size-exclusion chromatography (SEC). The solvent gradient used comprises a poor solvent (water, methanol, acetonitrile) and increasing amounts of a good solvent such as tetrahydrofuran. 

Divinyl ether monomers undergo cyclopolymerization under free-radical as well as cationic conditions. If the polymerizations are carried to high conversion (>30 to 35%), gelation occurs. However, the soluble polymers that are produced at high dilution and low conversion often have rather complex backbone structures. For example, the polymerization of divinyl ether proceeds to give a polymer that incorporates tetrahydrofuran, vinyloxy, and dioxabicyclo[3.3.0]octane units [137,138] ... 

Chiral ( )-crotylsilanes give tetrahydrofurans, cyclohexanones lead to spiro[4,51decane through a-(silylmethyl)divinyl ketone substitution, P-(alkoxycatbonyl)allylsilanes with epoxides give a-methylene-y-lactones fused to carbocycles, benzyl cations add to give tetrahydronaphthalenes or dihydro(lf/)indenes while tricyclic -2-phenyl-4H-1,3,2-benzodioxaborins with allylSiMes give polycyclic chromans l. 

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