134 Synthesis and Characterization of Poly(methyl methacrylate)/SiO 2 Hybrid Membranes: Effect of Silica Contents on Membrane Structure Muhammad Ali Zulfikar 1) and Abdul Wahab Mohammad 2) 1) Department of Chemistry, Bandung Institute of Technology, Bandung 2) Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, Malaysia e-mail: zulfikar@chem.itb.ac.id Received December 2005, accepted for publication December 2006 Abstract Hybrid organic-inorganic based on poly(methyl methacrylate)/SiO 2 (PMMA/silica) membranes were prepared using sol-gel technique under acidic conditions with different tetraethoxy orthosilane (TEOS) concentration. The thin membrane films were characterized using water permeability, water uptake, size porosity, Fourier Transform Infra Red (FTIR) and SEM analysis. Dispersion of particles in the nano scale was only possible with addition of TEOS above 10%. Organic-inorganic solutions with compositions varying from 100 PMMA/ TEOS 0 to 75 PMMA/25 TEOS were used to cast the asymmetric membranes. Water permeability, water up take and porosity size increase as TEOS content increases. SEM analysis showed that the membrane morphology changed from co-continuous phase to nodule structure if 10% TEOS was added, then return to co-continuous phase again when above 15% of TEOS was added. Keywords: Hybrid organic-inorganic membranes, PMMA/TEOS, Sol-gel, Structure Abstrak Membran hibrid organik-anorganik yang menggunakan poli(metil metakrilat)/SiO 2 telah berhasil disintesis menggunakan teknik sol-gel pada kondisi asam pada berbagai kandungan tetraethoxy orthosilan (TEOS). Karakterisasi film membran yang dihasilkan dikarakterisasi meliputi pengukuran permeabilitas terhadap air, kemampuan menyerap air, ukuran pori, Fourier Transform Infra Red(FTIR) dan analisis Scanning Electron Microscopy (SEM). Dispersi partikel pada skala nano hanya bisa diperoleh pada kandungan TEOS di atas 10%. Pada penelitian ini larutan campuran organik-anorganik dengan komposisi 100 PMMA/0 TEOS sampai 75 PMMA/25 TEOS digunakan untuk mencetak membran. Hasil analisis menunjukkan bahwa permeabilitas terhadap air, penyerapan air dan ukuran pori meningkat dengan meningkatnya kandungan TEOS. Hasil analisis SEM menunjukkan bahwa morfologi membran berubah dari struktur co-continuous menjadi struktur nodular ketika kandungan TEOS 10%, kemudian berubah kembali menjadi struktur co-continuous jika kandungan TEOS di atas 15%. Kata kunci: Membran organik-anorganik, PMMA/TEOS, Sol-gel, Struktur 1. Introduction Polymer hybrids have a great potential for the design of innovative membranes, which have been relatively seldom explored until now. In membrane application the use of hybrids is a promising strategy, which may contribute in solving some problems connected to organic and inorganic membranes. Asymmetric porous structures were extensively explored in the last decades as membranes for reverse osmosis, ultra- and microfltration or as supports for membranes. Several polymeric materials have been applied in preparing these membranes, starting with cellulose derivatives, and later, polymers with higher chemical and thermal stability such as polysulfone, poly(vinylidene fluoride) and poly(ether imide). Membrane preparation from organic polymers using the phase inversion method profits from morphology and final characteristics, because it can be controlled by a variation of parameters such as composition of casting solution and coagulation bath, and temperature. For applications where high thermal stability is decisive, inorganic membranes are the only solution. The possibility of combining properties of organic and inorganic materials have been explored some years ago. One aspect was the development of composite membranes using a ceramic porous support and a selective top layer of an organic or hybrid polymer (Moadded and Koros, 1997; Castro et al., 1996). The introduction of high contents of inorganic particles (ZrO 2 with average grain size 1 mm) to polysulfone membranes obtained by phase inversion was reported by Schaep and Vandecasteele (1998), Genne et al. (1996) and Doyen et al. (1996). An addition of colloidal silica to a polyimide matrix was used by Moadded and Koros (1996) to improve the O 2 /N 2 separation. Polyimide-silica hybrids with covalent bonds between the organic and inorganic segments have been synthesized by performing the