Synthesis and Structural Characteristics of Polycerams
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SYNTHESIS AND STRUCTURAL CHARACTERISTICS OF POLYCERAMS J.M. Boulton, H.H. Fox, G.F. Neilson and D.R. Uhlmann, Department of Materials Science and Engineering, University of Arizona, Tucson, AZ 85721. ABSTRACT Sol-gel techniques are readily applicable to the preparation of Polycerams. These hybrid materials uniquely combine organic and inorganic functionalities at the molecular level. Polycerams have here been prepared from tetraethoxysilane and modified, functionalized polybutadiene, polyethylene oxide urethane and polyethyleneimine. The structures and physical characteristics of the materials are herein reported. INTRODUCTION Conceptually there are many ways to create organically modified ceramics (Polycerams). Various precursors can be used to tailor both the type and degree of organic modification. For example, organo-alkoxy silanes can be used effectively to prepare organically modified silicates [e.g. 1,2]. An alternative approach is the entrapment of monomers in a porous gel followed by subsequent polymerization; as an example, PMMA has been incorporated into silica gels [e.g. 3]. One attractive approach is the use of reactive, functional polymers which can co-condense with hydrolyzed alkoxides resulting in the formation of three-dimensional structures. Reactive polymers incorporated into silica-based Polycerams include polydimethylsiloxane, either silanol [4,5] or triethoxysilyl (6] terminated; triethoxysilyl terminated polytetramethylene oxide (7] and trimethoxysilyl functionalized polyimides and polyarylene ether ketones [8). Inorganic networks are not restricted to silica: e.g., polytetramethylene oxide has been incorporated into networks prepared from chelated Al alkoxides [9]. In this work, novel silica-based Polycerams have been prepared from functionalized organic polymers, namely triethoxysilyl modified 1,2-polybutadiene (MPBD), (N-triethoxysilylpropyl) 0polyethylene oxide urethane (MPEOU) and trimethoxysilylpropyl substituted polyethyleneimine (MPEI). EXPERIMENTAL Tetraethoxysilane (TEOS) and modified polymers were obtained from Petrarch (Bristol, PA). The MPBD was received as a 50 wgt. pct. toluene solution; the MPEI was 50 wgt. pct. in iso-propanol (IPA); and the MPEOU was neat. All other reagents were reagent grade. The first step in preparing MPBD and MPEOU Polycerams was the same: TEOS and H20 (acidified with 0.19 M ptoluene sulfonic acid) were reacted by refluxing at a 2:1 H20: TEOS molar ratio for 15 min. in tetrahydrofuran (THF) with lg TEOS: 3 ml THF. The MPEI reactions were similar except IPA was the solvent (MPEI is insoluble in THF). Next the modified polymer was added. With MPBD and MPEOU, the reaction mixture was refluxed for 30 min., whereas with MPEI the solution was cooled to room temperature. This was due to the short gelation times of MPEI solutions. The reaction mixtures were poured into polypropylene beakers and loosely covered with foil. The MPBD Mat. Res. Soc. Symp. Proc. Vol. 180. @1990 Materials Research Society
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and MPEOU solutions all gelled within 36 hours, while th
