Synthesis and Characterization of Novel Saponified Guar-Graft-Poly(acrylonitrile)/Silica Nanocomposite Materials Vandana Singh, 1 Ashutosh Tiwari, 1* Sadanand Pandey, 1 Somit K. Singh, 1 Rashmi Sanghi 2 1 Department of Chemistry, University of Allahabad, Allahabad 211002, India 2 302 Southern Laboratories, Facility for Ecological and Analytical Testing, Indian Institute of Technology, Kanpur 208016, India Received 3 March 2006; accepted 4 September 2006 DOI 10.1002/app.25585 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The combination of carbohydrates with sili- con-based ceramic materials offers attractive means of pro- duction for high performance materials. Present article describes the synthesis of novel nanocomposites out of SiO 2 and saponified guar-graft-poly(acrylonitrile) (SG). Tetra- ethoxysilane was used as the precursor for silica and growth of SiO 2 phase was allowed concurrently in the pres- ence of SG. The material so obtained was thermally treated at 808C, 1608C, 5008C, and 9008C to study the effect of thermal curing on its properties. During the curing process, silanol surface groups of silica globules reacted to create the reinforced SiO 2 -SG substance. It was observed that at 9008C, the SiO 2 phase crystallized out in tetragonal shape (similar to Cristobalite form of silica) in presence of SG. The chemi- cal, structural and textural characteristics of the composites were determined by FTIR, XRD, TGA-DTA, SEM and BET studies. The materials were also evaluated as efficient Zn 2þ metal binder. Ó 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 536–544, 2007 Key words: saponified guar-graft-poly(acrylonitrile); silica; sol–gel method; metal ion binder INTRODUCTION Organic–inorganic composites of organic polymers and silica constitute an important class of advanced materials. Most of the polymeric materials used for making such hybrids are derived from continuously depleting petrochemical resources. Materials with high performance from renewable sources and with sufficient shelf life coupled with their ultimate bio- degradability are the need of the day. Silicate-filled polymer composites often exhibit remarkable im- provement in mechanical, thermal, and physicochem- ical properties when compared with pure polymers and their conventional microcomposites due to the nano-level interactions with the polymer matrix. Thus, the biopolymer silica composites prepared by the sol–gel processes in aqueous solutions, owing to their promising properties, are of special interest. 1–5 Tetramethoxysilane (TMOS) 6 and tetraethoxysilane (TEOS) 7 are currently used as precursors. Sol–gel syn- thesis of composite materials 8–11 allows the produc- tion of materials in which it is possible to control both particle size and shape and sometimes even the final packing of the colloidal particles. The combined or- ganic–inorganic characteristics of the composites rep- resent an improvement upon some of the thermal, mechanical, and porosity properties of the substance compared with the homologous characteristics of the lone individual organic and inorganic components. It has been observed that polysaccharides can serve as a template for silica generated in situ by the sol–gel processes, thus manipulating its synthesis as well as properties and structure. The polysaccharides pro- moted silica polymerization 12 through acceleration and catalysis of processes. Their effect is explicable by the formation of hydrogen bonds between hydroxyl groups of macromolecules and silanols generated by the hydrolysis of precursor. Guar gum is a commercially available, industrially important 13,14 polysaccharide material having back- bone of b-D (1 ? 4) mannopyranosyl units with a-D- galactopyranosyl units as side chains. Though tre- mendously used in industry, guar gum is rarely used in its natural form due to its quick biodegrada- tion. 15,16 Grafting of vinyl monomers significantly improves its shelf life 5 and the grafted guar gum finds various commercial applications. 17 Grafting of poly(acrylonitrile) on to guar gum followed by its sa- ponification offer grafted material bearing COOH/ CONH 2 groups 18,19 and potentially such material is *Present address: Division of Engineering Material, National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India. Correspondence to: V. Singh (singhvandanasingh@ rediffmail.com). Contract grant sponsor: Department of Science and Technology, Govt. of India. Journal of Applied Polymer Science, Vol. 104, 536–544 (2007) V V C 2007 Wiley Periodicals, Inc.