POLYMERS FOR ADVANCED TECH OLOGIESKJIHGFEDCBA Polym. Adv. Technol, 2005; 16: 681-687 Published online in Wiley InterScience (www.interscience.wiley.com).ZYXWVUTSRQPONMLKJIHGFEDCBA 001: 10.1002/pat.644WVUTSRQPONMLKJIHGFEDCBA Crosslinked styrene-maleic acid copolymer complexes of some transition metals and their adsorption behavior DCBA P. C. Deb*, L. D. Rajput, A. K. Agrawal, P. K. Singh, V. Hande and S. Sasane Naval Materials Research Laboratory, Shil-Badlapur Road, MIDC Area, Addl. Ambernath, Ambernath (E)- 421506, India Received 8 April 2005; Revised 23 May 2005; Accepted 4 July 2005 Transition metal complexes of linear and crosslinked styrene-maleic acid copolymer were prepared in ethyl alcohol. The complexes appear as micro clusters fairly uniformly distributed in the copo- lymer matrix. Vapor adsorption-desorption studies of the complex beads with methyl isobutyl ketone (MIBK), toluene and ethyl alcohol show initial fast release followed by a steady and slow release. Hydrogen adsorption at room temperature was studied for a few complexes up to about 650torr, which showed initial slow adsorption followed by a rapid increase at about 550torr. Copyright © 2005 John Wiley & Sons, Ltd. KEYWORDS: styrene-maleic acid copolymer; transition metal complexes; adsorption; crosslinking; matrix INTRODUCTION Metal complexes of organic compounds with functional groups have aroused intense interest in recent years in view of their potential in catalysis, separation, absorption and bio- medical applications.Y'" Of particular importance are the metal-organic frameworks which appear to retain substantial proportion of gases such as N 2 , CO 2 , H2 and organic vapors in the molecular pores at pressures of 1-20 etrnospheres.v '! Hydrogen absorption and retention capacities reach as high as 2% by weight at room temperature and lObar for representative metal-organic frameworks consisting of Zn- carboxylate complexes containing naphthalene and cyclo- butylbenzene linkers having designed frarneworks.l ' Recently, it has been observed that metal complexes with polymeric ligands such as polycaboxylic acid copolymers show unique properties like ion exchange, catalysis, electrical conductivity, etc. 12 - 15 Kavlaket al. 16 have carried out detailed studies on interaction of polytmaleic anhydride-alt-acrylic acid) with transition metal ions through UV-vis spectroscopy and viscometry. Their studies indicated preferential intra- chain complex formation, particularly at moderate-to-low concentration of the polymer. Michinobu et al.l? have described synthesis of micro-particles of Gd-polymethacrylic acid complex and studies on their magnetic signals. Even though multi-dentate organic molecules give rise to giant molecular complexes with transition metals, use of well defined nano and micro polymer ligands with reactive func- tional groups provide an excellent opportunity to prepare macro-molecular complexes as the size and shape of active macromolecules can be tailor-made through emulsion or suspension polymerization. 'Correspondence to: P. C. Deb, Naval Materials Research Labora- tory, Shil-Badlapur Road, MIDC Area, Add!. Ambernath, Ambernath (E)- 421506, India. E-mail: pramil_cd@yahoo.co.in Styrene and maleic anhydride are known to form alter- nating copolymers over a wide range of monomer-pair composition. 18 - 21 Hydrolysis of this copolymer gives styrene- maleic acid copolymers of well-defined structure where each pair of carboxylic acid groups are separated by at least one styrene unit. Crosslinked polymer beads of this copoly- mer are expected to contain immobilized functional groups devoid of long-range interactions. Mostly the frozen seg- ments in between crosslinks that are near neighbors should react with metal ions and from identifiable clusters. These molecular clusters along with inherent porosity of the crosslinked beads are expected to offer interesting properties such as gas and vapor absorption and retention. Introduction of specific hosts" may also facilitate controlling the size of micro and nano pores thus allowing selective molecular retention of specific size, shape and chemical nature. In this article the preparation of linear and essentially mono-dispersed crosslinked beads of styrene-maleic acid copolymer, their reaction with metal ions such as Cu t 2, Ni+ 2 , Co+ 2 , Fe+ 3 , Ti+ 4 and Pt+4 and vapor/gas uptake and retention characteristics of the complexes are described. EXPERIMENTAL Synthesis of linear and crosslinked copolyacid Styrene was freed of inhibitor by the standard method, dried and distilled. Maleic anhydride was recrystallisted from chloroform just before use. Copolymerization of equimolar mixture of the monomers was carried out in l:4-dioxane (AR grade from Merck) at 60°C under N2 atmosphere using 0.5 mg/ ml azo-bis-isobutyronitrile re-crystallized from methanol. The copolymer was precipitated in a large excess of petroleum ether (40-60°C) and purified by repeated dissolution-precipitation technique. The dried polymer was dissolved in l(N) aq. NaOH solution and heated to about 70°C with stirring for 24 hr to ensure conversion of anhydride to acid. The product was precipitated in cone. HCI and Copyright r 2005 John Wiley & Sons, Ltd.