Die Angewandte Makromolekulare Chemie 259 (1998) 73–76 (Nr. 4554) 73 Mechanical properties and water vapor permeation of vinyltriethoxysilane/methyl methacrylate copolymers Tuncer C ¸ aykara 1, *, Mehmet S. Erog ˇlu 2 , Olgun Gu ¨ven 3 1 Department of Chemistry, Faculty of Art and Science, Gazi University, 06500 Bes ¸evler, Ankara, Turkey 2 TUBITAK – Marmara Research Centre, Department of Chemistry, P.O. Box 21, 41470 Gebze, Kocaeli, Turkey 3 Department of Chemistry, Hacettepe University, 06532 Beytepe, Ankara, Turkey (Received: 2 March 1998) SUMMARY: Methyl methacrylate (MMA) was copolymerized with vinyltriethoxysilane (VTES) using 60 Co- c-radiation at varying volume fractions of the liquid monomers in the feed. Thin copolymer films were pre- pared by casting tetrahydrofuran solutions of the copolymers on a mercury surface. The effect of the mole fraction of VTES in the copolymer on the glass transition temperatures, mechanical properties and water vapor permeabilities were investigated. Glass transition temperatures and mechanical properties decreased with increasing VTES content in the copolymer. However, the water vapor permeabilities were found to increase with the VTES content. The increased water vapor permeation was attributed to increased water solubility in the copolymers due to the presence of Si-O-bonds. ZUSAMMENFASSUNG: Methylmethacrylat (MMA) und Vinyltriethoxysilan (VTES) wurden in variieren- den Volumenanteilen unter Verwendung von 60 Co-c-Strahlung copolymerisiert. Du ¨nne Copolymerfilme wur- den durch Gießen von Lo ¨sungen der Copolymeren in Tetrahydrofuran auf Quecksilber hergestellt. Der Effekt des Molenbruches von VTES im Copolymeren auf die Glasu ¨bergangstemperaturen, die mechanischen Eigen- schaften und die Wasserdampfpermeabilita ¨t wurde untersucht. Die Glasu ¨bergangstemperaturen und die mechanischen Eigenschaften nahmen mit zunehmendem VTES-Gehalt im Copolymeren ab. Die Wasser- dampfpermeabilita ¨t erho ¨hte sich jedoch mit zunehmendem VTES-Gehalt. Die erho ¨hte Wasserdampfdurchla ¨s- sigkeit wird der durch die Anwesenheit von Si-O-Bindungen verbesserten Lo ¨slichkeit von Wasser in den Copolymeren zugeschrieben. Introduction Silicon-containing monomers and their polymers and copolymers have attracted special interest because they combine the beneficial properties of organic and silane groups in the same molecule. The common highlighted properties of these materials are extremely low glass tran- sition temperature, high chain flexibility, UV stability, biocompatibility, surface activity and high oxygen perme- ability 1) . Because of these exceptional properties, silicon- containing polymers have been used in a variety of areas such as surface modification, enzyme immobilization, gas separation, biomedical applications, etc. Therefore, a lot of work has been devoted to the observation of the improving effect of organosilicon materials on the afore- mentioned properties of different copolymers 2–9) . For many years organofunctional silanes have been widely used as coupling agents with an aim to improve the total adhesive strength and aging resistance of organic and inorganic substrates 4, 6, 8, 9) . In spite of these excep- tional and diverse properties of organofunctional silanes, their polymers generally have too low mechanical resis- tivity to be used directly as a polymer, and they show cold flow even at high molecular weights as in polysi- lanes. Therefore, a common way to minimize these unde- sirable properties and to make these materials useful for a broad variety of applications is to prepare copolymers and blend systems. Random copolymers of vinyltriethoxysilane (VTES) with methyl methacrylate (MMA) have been synthesized by radiation-induced polymerization. Recently we dis- cussed the physical and morphological characteristics and the surface properties of some of these copolymers 10, 11) . In this study, we report the mechanical properties and water vapor permeabilities of these copolymers. Experimental Materials The monomers vinyltriethoxysilane and methyl methacrylate were obtained from Merck and purified by vacuum distilla- * Correspondence author. Die Angewandte Makromolekulare Chemie 259 i WILEY-VCH Verlag GmbH,D-69451 Weinheim 1998 0003-3146/98/0910–0073$17.50+.50/0