Date of Award
Master of Science
Materials Science and Engineering
Michael R. Kessler
In this work the dielectric and mechanical properties of neat polydicyclopentadiene (polyDCPD) as well as polyDCPD-polyaniline and polyDCPD-BaTiO3 composites were investigated. Neat matrix properties were tested extensively to probe the effects that the reaction retardant triphenylphosphine (PPh3) may have on the desired macroscopic properties. The addition of PPh3 was necessary for processing of ceramic filled composites to successfully suspend nanoparticles in the polymerizing solution. In order to achieve this level of kinetic control, switching catalysts from the 1st generation Grubbs (which was used during the polyDCPD-PANI investigation) to 2nd generation was required because of its affinity towards PPh3. According to the acquired data there is no detrimental difference between the three catalytic systems therefore 2nd generation and PPh3was adopted without incurring any foreseeable drawbacks.
Mechanically, neat polyDCPD samples that were polymerized with 2nd generation and PPh3 show from dynamic mechanical analysis (DMA) that the system has an average glassy modulus around 1 GPa with slight variations but show even smaller differences in the Tg. Across the concentration range studied (.05 - .3 wt %) there was no visible trend in the dielectric permittivity data. There is however a reasonably systematic rise in tan δ with concentration, suggesting possibly that catalyst concentration has an effect on the relaxation mechanisms. Dielectric breakdown strength characterization has also been employed and is portrayed here using Weibull distributions. Steep slopes in a Weibull plot correspond to small error bars on a single averaged point. Values on the y-axis will give the percent likelihood of failure at that specific voltage. In terms of the current system, variation is again minimal.
Upon the introduction of conducting organic polyaniline (PANI) particles or inorganic BaTiO3 (BTO) particles to the system it was possible to get significant increases in the permittivity at low frequencies and relatively low volume percents. The main concern about these two systems is that of their already remarkably high tan δ, which can be at least partially attributed to the particle size and weak particle-matrix interfaces in the PANI and BTO systems respectively.
Gottschalk, Diana, "Use of polydicyclopentadiene as a matrix in composite structural capacitors" (2011). Graduate Theses and Dissertations. 10260.