Hybrid Organic-inorganic Composites Research Articles

The Use of Functionalized Polybenzoxazoles and Polybenzobisthiazoles in Polymer-Silica Hybrid Materials

Hybrid organic-inorganic composites were prepared by precipitating silica into hydroxypolybenzoxazole (HPBO) and sulfopolybenzobishiazole (SPBT) polymers, with interfacial bonding between the phases improved by use of isocyanato-propyltriethoxy silane and N,N-diethylaminopropyltrimethoxy silane, respectively. The resulting materials were characterized with regard to their transparency, silica particle distribution, tensile modulus and tensile strength, thermal stability, and tendency to absorb water. 68 refs., 2 figs., 1 tab.

Structure/Property Behavior of Organic-Inorganic Semi-IPNS

Ongoing work in our laboratories continues to demonstrate the unique properties that can be developed by the generation of a glassy semi-interpenetrating network (SIPN) within an elastomeric-based hybrid organic-inorganic composite. The hybrids are synthesized by the acid catalyzed sol-gel-processing of triethoxysilane end-capped poly(tetramethylene oxide) (PTMO) and tetraethoxysilane (TEOS) in an alcoholic solution. The SIPNs are then created by swelling these hybrids with methacrylic acid (MAA) and then gamma-polymerizing the monomer in-situ. The resulting materials exhibit excellent optical transparency and significantly improved toughness. This paper reports on the effect of inorganic loading upon the mechanical properties of acid catalyzed hybrid composites. The results demonstrate that as the amount of TEOS added to the sol prior to gelation increases the elongation-to-break decreases and the stress-to-break increases. Similarly, the post-yield stress drop and post-yield elongation prior to strain hardening increase with increasing inorganic loading. Atomic force microscopy and small angle X-ray scattering data is presented which substantiates the morphological model developed to explain the mechanical response.

Preparation, Characterization and Properties of New Ion-Conducting Ormolytes

Two families of hybrid organic-inorganic composites exhibiting ionic conduction properties, so called ORMOLYTES (organically modified electrolytes), have been prepared by the sol-gel process. The first family has been prepared from a mixture of 3-isocyanatopropyltriethoxysilane (IsoTrEOS), O,O′ Bis (2-aminopropyl)polyethyleneglycol and lithium salt. These materials present chemical bonds between the organic (polymer) and the inorganic (silica) phases. The second family has been prepared by an ultrasonic method from a mixture of tetraethoxysilane (TEOS), polyethyleneglycol and lithium salt. The organic and inorganic phases are not chemically bonded. The Li+ ionic conductivity has been studied by AC impedance spectroscopy up to 100 °C. Values of aσ up to 10−4 Scm−1 have been found at room temperature. The conduction properties have been related to the materials structure using linewidth and relaxation times NMR measurements of 7Li between −100 °C and 90 °C. A systematic study has been done changing the lithium concentration, the polymer chain length and the polymer to silica weight ratio. The structures and the ionic conduction properties of both families are compared with emphasis on the nature of the bonds between the organic and inorganic components.

Investigation of Ion-Conducting Ormolytes: Structure-Property Relationships

Hybrid organic-inorganic composites with ionic properties, so called ormolytes (organically modified electrolytes) have been prepared by the sol-gel process from mixtures of tetraethoxysilane, tetraethylene glycol, and lithium salt. They show ionic conductivity up to 5 x 10-5 Ω-1 cm-1, with activation energies around 0.6 eV. Their properties have been related to their structure using a multitechnique approach (IR, DSC, NMR, SAXS). These materials can be described as diphasic systems with silica clusters providing the mechanical properties and the organic phase allowing the dissolution of large quantities of salts. Optical transparency and mechanical stability can be explained by the interpenetration of these two phases at a molecular level.