Synthesis and characterization of latent reactive oligo(oxyethylene)/carbosilane and carbosiloxane/carbosilane copolymers via acyclic diene metathesis polymerization (ADMET) for thermoset materials

Elastomeric materials can be found in many aspects of our life and the spectrum of their use is broad. From shoe soles, cable insulators, and automotive parts to advanced medical equipment, these polymeric materials are based on natural or synthetic rubbers such as butyl rubber or silicones. Although many of these products have been used for years, the development of novel synthetic methods for the improvement and creation of new classes of elastomers are continuously being sought.; Acyclic diene metathesis (ADMET) has been proven to be an effective tool in the synthesis of latent reactive carbosilane/carbosiloxane copolymers bearing a methoxy-functional group on each repeat unit. The polymerization results in a linear thermoplastic polymer. The latent reactive methoxy groups remain inert during polymerization; however, exposure to moisture triggers hydrolysis and the formation of a chemically crosslinked thermoset. The thermoset's properties can be modified by varying the ratio of carbosilane and carbosiloxane repeat units in the final material.; Synthetic modification of the crosslink density and run length in the soft phase in polycarbosilane/polycarbosiloxane elastomers is discussed. The incorporation of "chain-end" crosslinks has improved mechanical performance by limiting the formation of dangling chains. In addition, increasing the run length of the soft phase, to achieve a better balance between soft phase concentration and crosslink density, generates a material showing significantly improved mechanical performance.; Various oligo(oxyethylene) and carbosiloxane alpha, o-dienes with different lengths of oxyethylene or siloxane units and alkenyl chains have been synthesized to investigate their influence on the properties of the resultant materials.; Consequently, numerous thermoset materials that show physical properties from elastic to flexible plastic behavior were prepared and analyzed. The results obtained from mechanical testing and thermal analysis can be directly related to the structure of the thermoset.