Cellulose graft copolymerization

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... 

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. 

Graft copolymerization of acrylonitrile with various vinyl comonomers such as methyl acrylate, ethyl acrylate, vinyl acetate, and styrene onto cellulose derivatives using ceric ion was studied [24]. The results showed that... 

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. 

Recently, Li et al. [30], Yu et al. [31] reinvestigated the mechanism of graft copolymerization of vinyl monomers onto carbohydrates such as starch and cellulose initiated by the Ce(IV) ion with some new results as mentioned in Section II. Furthermore, they investigated the mechanism of model graft copolymerization of vinyl monomers onto chitosan [51]. They chose the compounds containing adjacent hydroxyl-amine structures, such as D-glucosamine, /mn5-2-amino-cyclohexanol, 2-... 

An effective method of NVF chemical modification is graft copolymerization [34,35]. This reaction is initiated by free radicals of the cellulose molecule. The cellulose is treated with an aqueous solution with selected ions and is exposed to a high-energy radiation. Then, the cellulose molecule cracks and radicals are formed. Afterwards, the radical sites of the cellulose are treated with a suitable solution (compatible with the polymer matrix), for example vinyl monomer [35] acrylonitrile [34], methyl methacrylate [47], polystyrene [41]. The resulting copolymer possesses properties characteristic of both fibrous cellulose and grafted polymer. 

Graft copolymerization can be initiated by physical or chemical processes. This paper describes methods for chemical initiation of grafting onto cellulosic fibers with special emphasis on recent developments, i.e. studies from the last 10-15 years. The initiation reactions may be free radical or ionic processes. The grafting reaction may also be a condensation or addition process. 

Peracetic acid, formed in situ from acetic acid and hydrogen peroxide in acid aqueous solution, was found to initiate graft copolymerization of vinyl monomers, e.g. methyl methacrylate and 4-vinyl pyridine, onto wood and cellulosic fibers at a good rate (1-3 h time) at 60°C2. The initiati on reaction is not specific for grafting and considerable amounts of homopolymer is formed. 

The graft copolymerization of acrylonitrile and of styrene onto regenerated celluloses, such as viscose rayon and cellophane, and onto cellulose acetate has been investigated by Pikler, Suta, and Alfoeldi (68) and by Alfoeldi and Pasteka (69). In both studies the authors used ozonized substrate for initiating the graft copolymerization. 

Also other oxidants have been used successfully to initiate graft copolymerization onto cellulose substrates. Toyo Rayon (79) achieved grafting by pretreatment of viscose rayon fibers with potassium permanganate-sulfuric acid and contacting it subsequently with acrylonitrile. Methyl methacrylate is being grafted to rayon when heated together with potassium bromate, as claimed by Asahi Chemical Industry... 

A specific way of grafting onto cellulose with respect to the attachment points of the side chains is being given through the introduction of polymerizable substituents. As mentioned at the beginning of this article, already in 1943 Usakov (2) synthesized vinyl and allyl esters of cellulose and made copolymerization experiments with maleic esters. 

Berlin, and Makarova (85) took up this approach ten years later and prepared the methacrylic esters of cellulose which could be polymerized to cross-linked products. They also descibed the graft copolymerization with methyl methacrylate, although, they did not recognize at that time their products as graft copolymers. 

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