Azobisisobutyronitrile, poly

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). 

The same authors proposed an alternative methods for obtaining soluble poly(/i-vinylborazine) homopolymers and poly(styrene-co-B-vinylborazine) copolymers 28 In fact, gentle polymerization conditions in solution at 80°C using Azobisisobutyronitrile (AIBN) (1.6 mol%) as an initiator provided soluble homopolymers. The polymer displays typical Mw and Mn values of —18,000 and 11,000, respectively, whereas an increase in the AIBN concentration results in a decrease in the molecular weight, contrary to what is usually observed in free-radical polymerization. 

Poly(styrene) and PMMA were synthesized from their respective monomers using azobisisobutyronitrile-initiated radical polymerization in benzene. Four freeze-pump-thaw cycles were used to degas the monomer solutions and polymerization was carried out for 48 hours at 60°C. The polymers were purified by multiple reprecipitations from dichloromethane into methanol. Films of these polymers were prepared and found to be free of any fluorescent impurity. 

To make further use of the azo-initiator, tethered diblock copolymers were prepared using reversible addition fragmentation transfer (RAFT) polymerization. Baum and co-workers [51] were able to make PS diblock copolymer brushes with either PMMA or poly(dimethylacrylamide) (PDMA) from a surface immobihzed azo-initiator in the presence of 2-phenylprop-2-yl dithiobenzoate as a chain transfer agent (Scheme 3). The properties of the diblock copolymer brushes produced can be seen in Table 1. The addition of a free initiator, 2,2 -azobisisobutyronitrile (AIBN), was required in order to obtain a controlled polymerization and resulted in the formation of free polymer chains in solution. 

Because of its chemical inertness, no direct way of curing poly(thiocarbonyl fluoride) has been found. However, creep has been reduced and strength at elevated temperatures improved by milling into the polymer a free-radical generator, such as dicumyl peroxide or azobisisobutyronitrile, and a free-radical acceptor, such as N,N -m-phenylenebismaleimide or triacryloylhexahydro-s-triazine, and curing with heat and pressure (65). A better method is to mill in divinylbenzene and a small amount of benzoyl peroxide and cure with heat and pressure (66). The divinylbenzene forms a crosslinked matrix that mechanically traps poly(thio-carbonyl fluoride) molecules. Since the elastomer is in effect filled with poly(di-vinyl benzene), the final composition is less resilient than untreated poly(thio-carbonyl fluoride). 

Polymerization. Poly (methyl methacrylate) was obtained commercially. The polymers of other methacrylates and their copolymers were prepared in toluene with 2,2 -azobisisobutyronitrile (AIBN) at 60 °C. All the polymers prepared free radically were syndiotactic or atactic. Isotactic poly(a,a-dimethylbenzyl methacrylate) was obtained using C6H5MgBr as the initiator in toluene at 0°C. Poly(methacrylic acid) was prepared in water using potassium persulfate at as the initiator 60 °C. The molecular weights, glass transition temperatures and tacticities of the polymethacrylates are summarized in Table I. 

A 0.056-g sample of AIBN (2,2 -azobisisobutyronitrile) is placed into a one-piece 100-mL flask (such as Chemglass AF-0522-02)t equipped with a Teflon vacuum stopcock and a magnetic stir bar, and the flask is evacuated at — 196°C. A 1.69-g (15.9 mmol) sample of B-vinylborazine (prepared by the procedure described above) is vacuum distilled into the flask. Three freeze-pump-thaw cycles are performed in order to remove any traces of oxygen. The stopcock is closed and the reaction flask is removed to a shielded hood where it is heated in an oil bath at 70°C for about 3 h, at which point the material is sufficiently viscous that the stir bar stops. Then 5 mL of benzene is condensed into the flask and the solution is heated at 70°C for another 9 h. Slow addition of the benzene solution into 40 mL of pentane under inert atmosphere affords the precipitation of 0.73 g (43.2% yield) of poly(B-vinyl-borazine). The polymer is filtered under nitrogen and dried in vacuo for about 5 min. 

Zhang s group in China developed monolithic poly(styrene-co-divinylbenzene) CEC column in which EOF is supported by carboxyl groups of polymerized methacrylic acid units (Xiong etal. [51]). In a typical procedure, vinylized 75 mm i.d. capillaries were filled with a mixture of 5% styrene 21, 10% divinylbenzene 22, 5% methacrylic acid 1, and 80% toluene containing 1% azobisisobutyronitrile (in respect to monomers) and polymerized at 70°C for 24 h. The pore volume of 0.098 mL/g and mean pore size of 40 nm determined for this monolith appear to be rather small and do not correspond with the published SEM pictures that reveal existence of large pores, and the chromatographic performance of the columns in CEC mode. 

Two of the polystyrene samples were benzoyl peroxide-initiated commercial materials one of these had been on the shelf for over twenty years. The poly (n-butyl methacrylate) and the poly (vinyl chloride) were also commercial materials. The poly (methyl methacrylate) and the third polystyrene sample were prepared under nitrogen from freshly distilled monomers by bulk initiation with azobisisobutyronitrile (AIBN). Each of the above samples was purified by two reprecipitations from tetrahydrofuran solution with methanol and dried in vacuum at 65 °C. for at least 24 hours. The poly (ethylene terephthalate) was a sample of 5-mil Mylar Type A sheet which had been cleaned by detergent washing and water rinsing, followed by vacuum-drying at room temperature for 16 hours. 

The synthesis of poly(butyl acrylate) in the presence of cysteine was carried out using THF, ethyl alcohol, and water where the molar ratio of butyl acrylate monomer/ cysteine/azobisisobutyronitrile was 1000 30 1, respectively. The mixture was then refluxed for 6 hours at 65°C while under constant stirring. After cooling the cysteine-modified product consisted of a white precipitate dispersed within poly(butyl acrylate). The precipitate was isolated from the polymer by dissolving the poly(butyl acrylate) in THF and filtering. 

Three 500-ml flasks were each charged with a mixture consisting of the Step 1 product (1 g) having an 8.1 mol% double bond content, poly(ethylene glycol) methacrylate (3.6 g Mn = 360 daltons), and 50 ml of THE. The flasks were placed into a bath heated to 70°C. Each mixture was then treated with 2,2 -azobisisobutyronitrile (2.7 mg, 9 mg, and 18 mg, respectively) and heated 25 hours and precipitated in methanol. The polymers were then washed three times with methanol, dried, and the poly(ethylene glycol) content determined to be 16.6,18.4, and 7.0 mol%, respectively. Polyethylene glycol incorporation scoping reactions are provided in Table 1. 

TABLE 1. Scoping reactions to determine the effect of 2,2 -azobisisobutyronitrile and reaction times on the incorporation of poly(ethylene methacrylate) into the Step 1 product, poly(lactide-g-butene). 

To prepare the graft copolymer, poly [(lactic-co-glycolic acid) (5.7 g) was dissolved in acrylic acid (5.7 g) and, upon dissolution, treated with 98% 2,2 -azobisisobutyronitrile (0.014 g). The mixture was then heated to 70°C and continued heating until the reaction mixture solidified. The solid was then placed into a vacuum oven to remove unreacted acrylic acid, and the product was isolated. 

A-Vinylformamide was converted into A-alkyl-A-vinylformamide derivatives by reacting it with an alkyl bromide in the presence of base. When A-vinylformamide intermediates were reacted with 2,2 -azobisisobutyronitrile, the polymer was obtained. Hydrolysis of poly(A-vinylformamide) generated an A-alkyl polyvinyla-mine, a versatile synthetic intermediate. 

Favier [2] used t-butyl dithiobenzoate, (II), as the chain transfer agent with 2,2 -azobisisobutyronitrile to prepare poly(A -acryIoyI morpholine), (111), having a Mn > 200,000 daltons with a polydispersity of 1.4. 

Reversible addition-fragmentation chain transfer (RAFT) polymerization using 2,2 -azobisisobutyronitrile and either A, A-dimethyl-5-thiobenzoylthiopropionamide or A-dimethyl-5-thiobenzoylthioacetamide as chain transfer agents has been used to prepare low polydispersity poly(A, A-dimethylacrylamide). The chain transfer agents were unusually effective in suppressing free radical termination reaction, thereby mimicking a living polymerization reaction. 

Materials. Poly(3-butenyltrimethylsilane sulfone) (PBTMSS) was synthesized by free-radical copolymerization of 3-butenyltrimethylsilane with liquid sulfur dioxide (molar ratio 1 9) initiated with azobisisobutyronitrile (AIBN) at 35X in a sealed glass ampoule. The detailed preparation procedure and properties of this copolymer have been reported elsewhere. (7 3)... 

SYNS ACETO AZIB AIBN a,a -AZOBISISO-BUTYLONITRILE AZOBISISOBUTYRONITRILE 2,2 -AZOBIS(ISOBUTYRONITRILE) 2,2 -AZOBIS(2-METHYLPROPIONITRILE) AZODIISOBUTYRO-NITRILE a,a -AZODIISOBUTYRONITRILE 2,2 -AZODIISOBUTYRONITRILE AZODIISOBUTYRO-NITRILE (DOT) 2,2 -DICYANO-2,2 -AZOPROPANE POLY-ZOLE AZDN POROFOR 57 VAZO 64... 

A 0.5 M solution of 7V,7V-dimethylaininoethyl methacrylate in a 1 9 ethanol-water mixture containing 2-10% by mass of poly(vinylpyrollidone) (PVP, molecular mass of 30,000 or of 360,000), 0.5% by mass of V,V -methylenebisacrylamide (both with respect to V,V-dimethylaminoethyl methacrylate), and 0.2g/dm of V,V -azobisisobutyronitrile was bubbled with nitrogen for 10 min and then heated at 65°C for 3 h. The product was then purified by microfiltration. 

Fig. 15.11 Schematic diagram of the preparation of Pt/poly(EVimBF )/MWCNT hybrids EG ethylene glycol, AIBN 2,2 -azobisisobutyronitrile)...

Reaction conditions 20% w/v TRIM based on volume of H2O, 2,2"-azobisisobutyronitrile (AIBN, 2% w/v), 0.5% w/v poly(vinyl alcohol) (88% hydrolyzed, 88,000 g/mol), 60 C, 6h. Mean diameter calculated fiom >100 particles. Measured by mercury intrusion porosimetry over the pore size range 7 nm-20 pm. Measured by N2 adsorption desorption using the Brunauer-Emmett-Teller method. 

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