Introduction Surface processes of modest size aromatic molecules on clay matrices have been of massive interest for elu- cidating the chemical reactivity and mechanical prop- erties of organo-clay composites [1–3]. The organo-clay composites which possess large specific surface area, considerable porosity and thermal stabil- ity have been widely used in a range of key processes as ion exchangers, selective adsorbents and reinforc- ing fillers for plastics and electric materials [4–6]. The host centres produced by immobilization of spe- cific guest molecules such as formamide, urea and short chain oil acids through strong hydrogen bonds into the inorganic matrices such as kaolinite are of great importance in catalyis [7–10]. Organic and inor- ganic molecules may form ‘intercalation compounds’ within the unique structure of kaolinite by overcom- ing the cohesive forces between free surface hydroxyl groups [11] whereas non-reacting molecules of large size are entrained by the precursors such as DMSO and NMF [7, 12]. Considerable attention has been paid to characterize the precursors to ordered org- ano-clay composites formed on kaolinite-type miner- als [13–15]. The benzamide species retained by pre-adsorbed DMSO composites at a kaolinite surface which should represent a clear possibility of new and prom- ising materials were examined in present work through the use of FTIR, thermal analysis (TG-DTG and DTA), X-ray powder diffraction (XRD) and sur- face area measurement techniques. Experimental XRD pattern of the kaolinite (K, Sigma, 212 mm) showed no crystalline impurities. DMSO [Fluka, 99.9%, (G.C.)] and benzamide (Fluka, ³98% (UV)) were used as received. 3 g K was mechanically stirred with 40 mL DMSO at 60°C for 2 days in a 50-mL flat-bottomed glass flask and the resulting kao- linite-dimethyl sulphoxide (K-DMSO) composite was washed with ethanol two times; the supernatant solution was centrifuged at 2000 rpm and the solid product was dried for 2 days at 60°C to eliminate the excess of DMSO [13, 14]. The displacement tech- nique (from the K-DMSO composite) was used to prepare the kaolinite-benzamide (K-Bz) intercalate. 1 g K-DMSO was thoroughly mixed with excess benzamide aqueous solution for 5 days at 130°C. The supernatant was discarded and the product washed twice with ethanol and subsequently by hot water. The solid product was dried for 2 days at 80°C and then sieved to 212 mm [9]. XRD profiles were recorded on a Rigaku 2000 instrument using Ni-filtered CuK a radiation (l, 1.54050 ) at 40 kV and 40 mA. Infrared spectra were collected in the 4000–200 cm –1 region with Mattson-1000 FTIR spectrometer at 4 cm –1 resolution using KBr pellet technique. Simultaneous TG-DTG and DTA curves were monitored using Rigaku TG 8110 analyser equipped with TAS 100 from room temperature to 1000°C at a heating rate of 10°C min –1 under nitrogen flow (calcinated a-alumina was taken as the reference). Surface areas were measured by nitrogen adsorption at 77 K using Quantachromosorb. 1388–6150/$20.00 Akadémiai Kiadó, Budapest, Hungary © 2007 Akadémiai Kiadó, Budapest Springer, Dordrecht, The Netherlands Journal of Thermal Analysis and Calorimetry, Vol. 87 (2007) 2, 429–432 BENZAMIDE SPECIES RETAINED BY DMSO COMPOSITES AT A KAOLINITE SURFACE B. Caglar, B. Afsin * and A. Tabak Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayis University, Kurupelit, Samsun, 55139 Turkey The surface area of kaolinite-benzamide (K-Bz) 6.62 m 2 g –1 , which is noticeably lower than that of kaolinite-dimethyl sulphoxide (K-DMSO) 14.61 m 2 g –1 , the co-perturbation of the inner-surface hydroxyl features at 3697 and 3650 cm –1 , and the increase of d(001) value by 7.44  are all related to the benzamide species inserted into the kaolinite structure through the replacement of the K-DMSO composites. Disappearance of the DMSO reflections and emergence of well-defined features at 6.04(2q) and 11.16(2q), 001 and 002 reflections with d values of 14.62 and 7.92 , respectively point out that the DMSO species were substituted efficiently by benzamide molecules. The thermal stability of the K-Bz derivative up to 300°C can be attributed to the slightly tilted aromatic ring keying into the gibbsitic sheets via the –NH 2 groups. Keywords: benzamide, DMSO, inner surface hydroxyls, kaolinite, preadsorption * Author for correspondence: bafsin@omu.edu.tr