Grafting microwave assisted synthesis

Another method of graft copolymer synthesis is a combination of microwave-based and conventional synthesis, i.e. using both microwave radiation as well as a chemical free radical initiator (e.g. ceric ammonium nitrate) together. This process is referred to as microwave assisted synthesis [47]. Although it yields a higher percentage grafting than the microwave initiated synthesis, the rehability of the synthesis process is low. 

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. 

Vijan, V, Kaity, S., Biswas, S., Isaac, J., and Ghosh, A. Microwave assisted synthesis and characterization of acrylamide grafted gellan application in drug delivery. Carbohydr. Polym., 90,496-506 (2012). 

S. Kaity, J. Isaac, P.M. Kumar, A. Bose, T.W. Wong, and A. Ghosh, Microwave assisted synthesis of acrylamide grafted locust bean gum and its application in drug delivery, Carbohydr. Polym., 98 (1), 1083-1094, 2013. 

S. Mishra, G. Sen, G.U. Rani, and S. Sinha, Microwave assisted synthesis of polyacrylamide grafted agar (Ag-g-PAM) and its apphcation as flocculant for wastewater treatment, Int. J. 

Sen G, Rani GU, Mishra S. Microwave assisted synthesis of poly(2-hydroxyethylmeth-aciylate) grafted agar (Ag-g-P(HEMA)) and its application as flocculant for wastewater treatment. Front Chem Sci Eng 2013 7 312-321. 

Rani P, Sen G, Mishra S, Jha U. Microwave assisted synthesis of polyacrylamide grafted gum ghatti and its application as flocculent. Carbohydr Polym 2012 89 275-281. 

Rani GU, Mishra S, Sen G, Jha U. Polyacrylamide grafted agar synthesis and appbcations of conventional and microwave assisted technique. Carbohydr Polym 2012 90 784-791. 

Synthesis of the Graft Copolymers by Microwave-Assisted Method... 

SCHEME 3.3 Mechanism of graft copolymer synthesis of polyacrylamide chains-grafted agar backbone by microwave-assisted technique. 

Sun et al. have also reported microwave-assisted S5mthetic process for bis-benzimidazolyl benzoxazole synthesis. IL-grafted 3-amino-4-hydroxy benzimidazolyl 100 was subjected with thiocarbonyl diimidazole under micro-wave irradiation followed by S-alkylation by various alkyl bromides at ambient temperature to afford IL-bound bis-benzimidazolyl benzoxazole 108 and subsequently basic methanolysis to remove IL support (Scheme 12) [45]. Present strategy is useful to obtain IL-intermediate and final product by simple operation, and short reaction time is observed under microwave dielectric heating. 

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