Structure/Property Behavior of Organic-Inorganic Semi-IPNS

Abstract

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.