Synthesis of partially carboxymethylated guar gum-g-4-vinyl pyridine and study of its water swelling, metal ion sorption and flocculation behaviour Jasaswini Tripathy, Dinesh Kumar Mishra, Abhishek Srivastava, Madan Mohan Mishra, Kunj Behari * Polymer Science Research Laboratory, Department of Chemistry, University of Allahabad, Allahabad 211002, India Received 13 August 2007; received in revised form 10 September 2007; accepted 14 September 2007 Available online 21 September 2007 Abstract Unreported graft copolymer of 4-vinyl pyridine (4VP) with partially carboxymethylated guar gum (Cmg) was synthesized and reac- tion conditions were optimised using a bromate/thiourea redox pair under an inert atmosphere at 40 °C. Studies have been done to observe the effect of reactants on grafting parameters by varying the reactant concentration. Grafting ratio, add on and conversion show a decrement on increasing the concentration of partially carboxymethylated guar gum beyond 1.0 g dm 3 . The grafting parameters increase on increasing the concentration of 4-vinyl pyridine from 13 · 10 2 to 25 · 10 2 mol dm 3 , BrO 3  from 4 · 10 3 to 10 · 10 3 mol dm 3 and thiourea from 1.6 · 10 3 to 4.8 · 10 3 mol dm 3 . Optimum temperature and time for grafting of 4-vinyl pyri- dine on partially carboxymethylated guar gum are found to be 40 °C and 120 min, respectively. Metal ion uptake and flocculation behav- iour have been also studied and found that graft copolymer shows enhancement in these properties than substrate. Swelling behaviour of graft copolymer has been investigated. The graft copolymer is characterized by FTIR and thermal analysis. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Graft copolymer; Metal ion sorption; Water swelling behaviour; Flocculating properties; Partially carboxymethylated guar gum; 4-Vinyl pyridine 1. Introduction Modification of natural polymers by graft copolymerisa- tion is anticipated to be quite promising technique as it functionalises these biopolymer to their potential, impart- ing desirable properties onto them. Thus, in recent years, much attention has been paid on chemical modification of these natural macromolecules through grafting (Behari, Pandey, Taunk, & Kumar, 2001; Pandey, Srivastava, Tri- pathy, & Behari, 2006; Srivastava, Banerjee, Mishra, & Behari, 2005). Partially carboxymethylated guar gum is a derivative of guar gum, which is a naturally occurring galactomannan polysaccharide isolated from the seed endosperm and hav- ing linear chain of b-D mannopyranose joined by (1–4) linking with a-D-galactopyranosyl units attached by 1,6 links in the ratio of 1:2 (Sinha & Kumria, 2001). Due to immense potential and low price, this versatile polymer is used as a vehicle for oral controlled release purpose (Skin- ner, Harcum, Barnum, & Guo, 1998). Guar gum and its derivatives find numerous other applications such as in oil industry they act as major ingredients in drilling muds and fingering fluids whereas in textile industry, help to improve printing quality (Turk & Schneider, 2000). Even though guar gum and its derivatives enjoy wide number of applications, however like other polysaccharides they are susceptible to easy biodegradation (Srivastava, Tripa- thy, Mishra, & Behari, 2007) which could be improved by grafting vinyl monomers onto them. 0144-8617/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2007.09.014 * Corresponding author. Tel.: +91 5322545354. E-mail address: kunjbehari1234@rediffmail.com (K. Behari). www.elsevier.com/locate/carbpol Available online at www.sciencedirect.com Carbohydrate Polymers 72 (2008) 462–472