Cellulose graft polymers, synthesis

This chapter reports successful initial efforts to bond wood in the presence of hydrophobic plastic material [polystyrene (PS)] using well-defined and tailored cellulose-polystyrene graft polymers as compatibilizers or interfacial agents. The synthesis of these tailored cellulose graft polymers is also presented. 

Most of the important syntheses of cellulosic graft polymers involve irradiation with high-energy beams. Ultraviolet and x-ray sources are sometimes used, but Co radiation is used most often (Chapiro, 1962). In an oversimplified manner, the synthesis can be described as follows (Chapiro, 1962, p. 600) ... 

In spite of these enormous efforts, there is still no large-scale commercial application of cellulose graft copolymers. The reasons for this situation and the challenge it represents to cellulose and polymer scientists and engineers will be the subject of this introductory paper. It is convenient to break down such a discussion into the following areas, synthesis, characterization, properties and, finally, applications. The discussion will be mainly devoted to cellulose itself, although grafting to cellulose derivatives has also been actively pursued. 

Mlshra, S., Rani, G. U., and Sen, G. (2012). Microwave initiated synthesis and application of pol3 crylic acid grafted carboxymethyl cellulose, Carbohydr. Polym.. 87,2255-2262. 

Kang FIL, Liu WY, Fie BQ, Shen D, Ma L, Huang Y (2006) Synthesis of amphiphilic ethyl cellulose grafting poly(acrylic acid) copolymers and their self-assembly morphologies in water. Polymer 47 7927-7934... 

Anionic and Cationic Polymerizations o Radical Polymerization Advances o Coordination Polymerizations 0 Step-Growth Polymerization Advances 0 Synthesis of Tactic Polymers o Stereoblock Copolymers o Dispersion Polymerizations o Cellulosic Graft Copolymers o Diels-Alder Polymer Forming Reactions o A New Path To Phenolic Resins o Nitrogen Heterocycle Polymerizations o Optically Active Polymers o Poly (Phenylene Sulfide) o Poly (Aryl Ethers) o (Poly (Aryl Ether Sulfones) o Epoxy and Isocyanate Resin Replacement o Azlactone Functionalized Oligomers o Epoxy Resin-Isocyanate Reactions o Chelating Polymers o Oxazoline Functionalized Polymers o Poly (Alkyl Methacrylates) o Macromers... 

In the same context, a critical review discusses the recent advances in graft polymerization techniques involving cellulose and its derivatives [137]. The study summarizes some of the features of cellulose structure and cellulose reactivity and describes the various techniques for grafting synthetic polymers from the cellulosic substrate. In addition to the traditional grafting techniques, the recent developments in polymer synthesis that allow increased control over the grafting process and permit the production of functional celluloses with improved physical and chemical properties, are highlighted. 

Narayan, R. (1988) Synthesis of Controlled Cellulose - Synthetic Polymer Graft Copolymer Structures in Cellulose Wood Chemistry and Technology, C. Schuerch (ed), John Wiley Sons New York, p.945. 

The enzymatic polymerization of lactones could be initiated at the hydroxy group of the polymer, which expanded to enzymatic synthesis of graft copolymers. The polymerization of c-CL using thermophilic lipase as catalyst in the presence of hydroxyethyl cellulose (HEC) film produced HEC-gra/f-poly( -CL) with degree of substitution from 0.10 to 0.32 [102]. 

Graft copolymers of nylon, protein, cellulose, starch, copolymers, or vinyl alcohol have been prepared by the reaction of ethylene oxide with these polymers. Graft copolymers are also produced when styrene is polymerized by Lewis acids in the presence of poly-p-methoxystyrene. The Merrifield synthesis of polypeptides is also based on graft copolymers formed from chloromethaylated PS. Thus, the variety of graft copolymers is great. 

Phase transfer catalysts have been grafted onto the surface of porous capsules to facilitate product purification after reaction, and many types of immobilized cells, mycelia, enzymes, and catalysts have been encapsulated in polymers such as PDMS, PVA, or cellulose. In the specific case of PVA, they are named Lenti-kats, as commercialized by Genialab and used for nitrate and nitrite reduction and in the synthesis of fine chemicals. These beads show minimized diffusion limitations caused by the swelling of the polymeric environment under the reaction conditions. To avoid catalyst leaching, enlargement can be realized by linking them to, e.g., chitosan. 

With respect to the other backbone polymers in UV grafting, PVC Is as expected whereas the results for the polyolefins, especially polyethylene, are surprising when compared with cellulose. The relatively high copolymerization yields with polyethylene may be attributed to the presence of trace impurities in the backbone polymer which are present during synthesis. These impurities sensitize the grafting process. 

H. Lbnnberg, L. Fogelstrbm, M. A. S. Azizi Samir, L. Berglund, E. Malmstrom, and A. Hult, Surface grafting of microfibrillated cellulose with poly( -caprolac-tone). Synthesis and characterization, Eur. Polym. J., 44 (2008) 2991-2997. 

Chauhan GS, Sharma R, Lai H (2004) Synthesis and characterization of graft copolymers of hydroxypropyl cellulose with acrylamide and some comonomers. J Appl Polym Sci 91 545-555... 

V.K. Thakur, M. K. Thakur, and R. K. Gupta, Graft copolymers from cellulose Synthesis, characterization and evaluation. Carbohydr. Polym. 97, 18-25 (2013). 

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