Alkyl phosphite inhibition of the frontal ring opening metathesis polymerization of dicyclopentadiene catalyzed by 2<sup>nd</sup> generation Grubbs catalyst has revealed a slow bulk polymerization at room temperature. The bulk polymerization did not result in spontaneous frontal polymerization, as with previous frontal polymerization chemistries, but instead, manifested as a liquid to gel transition. By tuning the concentration of alkyl phosphite, a variety of rheological profiles, including high-viscosity fluids and free-standing elastomeric gels, were obtained within several hours. The high-viscosity fluid was utilized for 3D printing via extrusion through a cooled print head onto a heated platform, which initiated the frontal polymerization. The elastomeric gels could be shaped, stamped with macro- and micro-patterns, or cut and joined before frontal polymerization. Frontal polymerization of the gel resulted in a structural thermoset fixed with the chosen morphology. To better understand the liquid to gel transition and optimize the preparation of frontally polymerizable gels, the degree of cure, shear storage and loss moduli, and polymerization front velocity in reactive formulations were tracked over time. The mechanical properties of the obtained thermosets were found to be independent of the amount of time the reactive formulation was aged, provided that frontal polymerization was sustained. The functional lifespan of the gels, the interfacial strength of gel-fused thermosets, and the applications of frontally polymerizable gels in on-demand production of complex structural parts will also be discussed.

Frontal polymerization of gels derived from dicyclopentadiene

255th National Meeting (2018)

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