Azobisisobutyronitrile as initiator

PVPA was prepared by the free-radical homopolymerization of vinyl-phosphonyl dichloride using azobisisobutyronitrile as initiator in a chlorinated solvent. The poly(vinylphosphonyl chloride) formed was then hydrolysed to PVPA (Ellis, 1989). No values are available for the apparent pA s of PVPA, but unpolymerized dibasic phosphonic acids have and values similar to those of orthophosphoric acid, i.e. 2 and 8 (Van Wazer, 1958). They are thus stronger acids than acrylic acid, which as a pK of 4-25, and it is to be expected that PVPA will be a stronger and more reactive acid than poly(acrylic acid). 

Materials. Polymer-bonded sensitizers and their model compounds are shown in Figure 2. Samples 1-5 were prepared by radical copolymerization of corresponding ethylenic monomers using azobisisobutyronitrile as initiator at 70°C in DMF(5) or DMF/H20 (9/1 for 1, 2 and 4 8/1 for 3) (15). Sample 7 was prepared by the same procedure as 6 (16). The copolymer compositions... 

Halogenation of hydrocarbons. Walling found /-butyl hypochlorite useful for light- or radical-induced chain chlorination of toluene. Thus, in the presence of azobisisobutyronitrile as initiator, the reaction with toluene at 40° affords benzyl chloride (84%), /-butanol (97%), and 1-3% each of chlorololuenes, methyl chloride, and acetone. 

Decarboxylation. Della and Patney recommend a two-step method for decarboxylation of bridgehead carboxylic acids. The first step is the Cristol-Firth modification of the Hunsdiecker reaction (I, 657, improved by use of methylene bromide as solvent). The second is photochemical reduction of the bromides by tri- -butyltin hydride (I, 1192-1193) with azobisisobutyronitrile as initiator. Yields are 80-95% in the first step and 80-90% in the second step. 

Copolymer SMC can be obtained by the copolymerization of styrene with 2-(methylsulfinyl)ethyl methacrylate at 70 C in toluene with azobisisobutyronitrile as initiator (4,5). 

Using azobisisobutyronitrile as initiator, ethylene can be copolymerized free-radically with vinyl acetate at 300-400 bar in t-butanol (low transfer constant). Products with vinyl acetate contents of over 10% give shrinkable films those with up to 30% vinyl acetate give thermoplastic materials and those with over 40 % give clear films. The products can be cross-linked with lauroyl peroxide on the addition of, for example, triallyl cyanurate. Copolymers of ethylene and ethyl acrylate have similar properties. 

Radical polymerization Bulk polymerization using azobisisobutyronitrile as initiator at 50°C (3)... 

Fig. 14. Average number of radicals per particles in dependence on both conversion and particle size and particle size in dependence on conversion for a batch styrene emulsion polymerization gray squares h versus conversion open squares h versus particle size gray circles D versus conversion. (Recipe 1000 g of water, 200 g of styrene, 4.268 g of SDS, and 1.74 g of 2,2 -azobisisobutyronitrile as initiator, temperature 60°C, for details see Ref 115.

Samples of poly(styrene sulfone) were prepared in pressure vessels at temperatures ranging from 50 to 70° using azobisisobutyronitrile as initiator and dimethylformamide as diluent. These reaction conditions afforded high yields of polysulfones with polydispersities of 1.5 to 2.5 (GPC) and with a sulfur content of 11-12%, as expected for 2 1 st]rrene-sulfur dioxide copolymers. 

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