Redox-initiated graft copolymerization

Mohanty AK, Singh BC (1987) Redox-initiated graft copolymerization onto modified jute fibers. J Appl Polym Sci 34 1325-1327... 

It is likely that Ce + and Mn ions initiate graft copolymerization by about the same mechanisms. Mn + ions have a lower redox potential ( 1.5 V) than CeH ions ( 1.7 V), and they appear to cause less side-reactions besides the radical formation. Industrial development of the Mn-5 initiator for grafting is under way. 

The hydroxyl radicals can react with cellulose, initiating graft copolymerization, or react with monomer, resulting in homopolymerization. A similar redox system is based on the use of ceric ions, which produce radicals by direct oxidation of the cellulose chains and thus initiate graft polymerization ... 

In aqueous solutions the persulphate ion is known as a strong oxidizing agent, either alone or with activators. Thus, it has been extensively used as the initiator of vinyl polymerization [43-47]. However, only later, Kulkarni et al. [48] reported the graft copolymerization of AN onto cellulose using the Na2S203/K2S20s redox system. 

Graft Copolymerization of Vinyl Monomers Onto Macromolecules Having Active Pendant Group via Ceric Ion Redox or Photo-Induced Charge-Transfer Initiation... 

Therefore, the graft copolymerization of vinyl monomers onto macromolecules having active an pendant group can be achieved either by redox initiation with a Ce(IV) ion or by photo-induced charge-transfer initiation with BP, depending on the structure of the active groups. 

The initiation of graft copolymerization using this redox system, seems to proceed in accordance with the following scheme ... 

Bamford, Eastmond and coworkers have employed metal complexpolymeric halide redox systems to initiate block and graft copolymerization. The polymeric halides can be synthesized by a variety of techniques, including radical polymerization,281 anionic polymerization (Scheme 7.28),"so... 

Initiation of graft copolymerization by radical mechanisms can occur by (a) a redox process on the substrate or (bl a chain transfer process to the substrate. In addition to grafting, formation of homopolymer may occur in both cases. 

The same authors (5) showed also in another work that the presence of larger amounts of lignin in bisulfite pulps may have a favourable effect on grafting polyacrylonitrile using the cellulose xanthate-hydrogen peroxide redox system to initiate the copolymerization reaction. The plots of the total conversion as well as of polymer loading show a minimum centered around approximately 15% of lignin. 

Thermoplasticization of Wood by Heterogeneous Graft Copolymerization (Redox Initiation). A redox grafting method using ferrous sulfate-hydrogene peroxide as the initiator was conducted to copolymerize MMA to wood meal. The results of grafting are shown in Table III. 

Table III. Redox Graft Copolymerization of MMA onto Wood Using Ferrous Sulfate - Hydrogen Peroxide as an Initiator...

Microwave-assisted synthesis of a guar-g-polyactylamide (G-g-PAA) has also been reported [80]. The reactions were performed in a domestic microwave oven. Graft copolymerization of the guar gum (GG) with acrylamide (AA) under the action of microwave irradiation in the absence of any radical initiators and catalyst resulted in grafting yields comparable with redox (potassium persulfate-ascorbic acid) initiated by conventional heating but in a very short reaction time. Grafting efficiency up to 20% was further increased when initiators and catalyst were used under microwave irradiation conditions. Maximum grafting efficiency achieved under MW conditions was 66.66% in 0.22 min, compared with 49.12% in 90 min by the conventional method. 

Several natural polymers as chitin, cellulose, functionalized cellulose and natural fibers are some of most studied natural polymers in graft copolymerization using redox system as initiator, being cerium ion one with more reports. 

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