Robert Stuart Maxwell

The hydrogenation of 1,4-diphenylbutadiyne (DPB) blended with carbon-supported Pd (DPB–Pd/C) in the form of pellets were investigated by isothermal isobaric experiments at 1333 Pa of H2 and in the temperature range of 291 K - 315 K. The extracted kinetics were then used in conjunction with complementary constant rate of H2 input experimentation to model the performance of DPB-catalysis/support system as a function of temperature and H2 partial pressure. First principles density functional theory (DFT) calculations were also performed to shed light on molecular level energetics of DPB and its intermediate states. A seemingly puzzling formation of alternate positive activation energy barrier (higher reaction rate with higher temperature) and negative activation energy barrier (higher reaction rate with lower temperature) zones during the hydrogenation process was discovered. However, this observed phenomenon can be logically explained in terms of associated phase changes and H2 transport in the material, and, in turn, provides a good illustration of a rarely encountered chemical process with a negative activation energy barrier.

The hydrogen uptake kinetics of 1,4-bis(phenylethynyl)benzene, or DEB, mixed with palladium (Pd) on activated carbon in a rubber matrix coating on top of a porous silicone foam substrate are investigated. First, isothermal isobaric hydrogenation experiments were performed under different temperatures and H2 pressures to extract the uptake kinetics. The H2 uptake models based on the measured kinetic parameters were then employed to investigate/simulate the performance of the getter under dynamic application environments. The actual hydrogenation characteristics in this type of getter is multifaceted and involve actual H2 concentration in the getter matrix, micrometer scale diffusion of atomic hydrogen away from Pd sites, precipitation of hydrogenated DEB crystals at the coating surfaces, and mobility of fresh DEB molecules. The kinetic analysis/modeling methodology described in this report can serve as a template for other gas-solid reactions as well. Besides possessing a good hydrogen capacity and excellent performance, this type of rubberized getter also offers some unique advantages over traditional solid getter: flexible structure and protection of Pd catalyst from exposure to the environment.

The shock response of polymers is important for a number of commercial and defense‐related applications, but it is difficult to obtain empirical shock response data over the wide range of preparations and aging conditions typically found in such applications. Ultrafast compression is useful to characterize polymer shock response over a wide range of polymer initial conditions due to the high throughput of this method. To establish greater confidence in ultrafast compression experiments and to characterize the detailed shock response of several variations in a single base polymer, the results of sub‐nanosecond shock compression experiments in ∼5 μm thick layers of the polydimethylsiloxane (PDMS)‐based elastomeric rubbers Sylgard‐184, SE1700, and an unfilled, end‐linked model PDMS network are presented. The results of conventional ultrafast shock etalon measurements to time‐of‐flight measurements for similar thickness layers of irradiated and unirradiated SE1700 are compared. Good agreement between the shock response measured by these two ultrafast shock methods, as well as consistency between ultrafast data and long time scale gas gun data is found. From measurements across a variety of PDMS formulations, a statistically significant variation in the shock response with the quasistatic elastic modulus is presented. Published 2018.^† J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 827–832