Azobisisobutyronitrile-initiated graft

Benzoyl Peroxide and Azobisisobutyronitrile-Initiated Graft Copolymerization. Cellulose nitrate (CN) (10 g) was dissolved in methyl isobutyl ketone (90 ml) in a three-necked flask and to this solution methyl methacrylate (10 ml) and benzoyl... 

In the presence of radical initiators such as benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), persulfates (S208 ), etc., grafting of vinyl monomers onto polymeric backbones involves generation of free radical sites by hydrogen abstraction and chain transfer processes as described below ... 

The hydrogen abstraction from —SH groups is faster than from —OH groups. Hebeish et al. [9] and Misra et al. [10,11] reported the chain-transfer method of initiation of graft copolymerization onto cellulosic substrates with azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO) as initiators. 

Grafting can also provide the monolithic polymers with rather unexpected properties. For example, the two-step grafting procedure summarized in Fig. 7, which involves the vinylization of the pore surface by reaction of the epoxide moiety with allyl amine, and a subsequent in situ radical polymerization of N-isopropylacrylamide (NIPAAm) initiated by azobisisobutyronitrile within these pores leads to a composite that changes its properties in response to external temperature [76]. 

Figure 10. Effect of initiator concentration on the graft copolymerization of methyl methacrylate onto cellulose nitrate initiated by a, benzoyl peroxide and b, azobisisobutyronitrile. Key O, grafting efficiency 9, percent grafting.

Azobisisobutyronitrile is used as a catalyst in vinyl polymerization and as a blowing agent for making foam rubber [114]. Azobisisobutyronitrile also is used as a free radical initiator (FRI) in graft copolymerization. 

Polyvinylpyrrolidone (PVNP) Grafting. PVNP was grafted onto Biomer by radiation copolymerization of N -vinylpyrollidone monomer (Polysciences, Inc.) onto the elastomer surface. Polymerization was ultraviolet radiation-initiated in a monomer solution containing 0.1% azobisisobutyronitrile (AIBN) (Polysciences, Inc.). 

Block and Graft Copolymer Stabilizers in Dispersion Polymerization. A sterically-stabilized, nonaqueous, polymer dispersion is made simply by heating a solution of a free radical initiator (e.g., azobisisobutyronitrile), an appropriate monomer, and a suitable block or graft copolymer in an organic liquid which is a nonsolvent for the polymer product and acts as a diluent for the dispersion. The block or graft copoly-... 

The reactivity of the initiating radicals toward the backbones can vary and this can also change the efficiency of grafting. Benzoyl peroxide initiated polymerizations of methyl methacrylate monomer, for instance, in the presence of polystyrene yield appreciable quantities of graft copolymers. Very little graft copolymers, however, form when di-r-butyl peroxide initiates the same reactions. Azobisisobutyronitrile also fails to yield appreciable quantities of graft copolymers. This is due to very inefficient chain transferring to the polymer backbones by r-butoxy and isobutyronitrile radicals. 

Graft copolymerization was carried out at 60°C in evacuated sealed ampoules using styrene as a monomer, azobisisobutyronitrile (AIBN) as an initiator and dimethylformamide(DMF) as a solvent. 

BPO) as initiator. If a,a -azobisisobutyronitrile (AIBN) is used instead of BPO no grafting is observed. This suggests that highly reactive primary radicals are responsible for attack on the rubber backbone. 

The hydrosols may be either linear, graft or branched polymers. The linear acrylic hydrosol polymers can be conveniently prepared by a conventional free radical solution polymerization process. Useful examples of initiators include dibenzoyl peroxide, hydrogen peroxide and other peroxy compounds such as tert-butyl peroxyp-ivalate, ferf-butyl peracetate, ferf-butyl peroctoate, and azo compounds such as 2,2 -azobisisobutyronitrile. The solvent used for the polymerization should be miscible with water so that the polymer can be conveniently inverted. 

The preparation of ZnO/ PS nanocomposites preceded as follows [112] First, 110 mg bare ZnO or 110 mg PMMA-grafted ZnO were added into a three-necked bottle. Then, 10 mL styrene was added into the reactor. The mixture was stirred with the aid of ultrasonic oscillation until a uniform dispersion of the ZnO particles in styrene was attained. Afterwards, 36 mg azobisisobutyronitrile (AIBN) was added into the reactor as initiator. The subsequent polymerization was conducted at 85°C for 2.5 h. Then, the obtained composites were dried under vacuum for 24 h. The differential scanning calorimetry (DSC) heating curves of neat PS, PS/ZnO (bare), and PS/ZnO (PMMA grafted) are shown in Fig. 10. DSC traces in Fig. 10a show that neat PS has a lower glass transition temperature (Tg = 87.7°C) than PS/ZnO (bare, 7 g = 97.9°C) and PS/ZnO (PMMA grafted, Tg = 95.3°C). This behavior can be explained by the restricting effect of the nanoparticles in polymer. ZnO... 

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