Accelerated Thermal Depolymerization of Cyclic Polyphthalaldehyde with a Polymeric Thermoacid Generator.

Thermally triggerable polymer films that degrade at modest temperatures (≈85 °C) are created from a blend of cyclic polyphthalaldehyde (cPPA) and a polymeric thermoacid generator, poly(vinyl tert-butyl carbonate sulfone) (PVtBCS). PVtBCS depolymerizes when heated, generating acid which initiates the depolymerization of cPPA into volatile byproducts. The mass loss onset for 2 wt% PVtBCS/cPPA is 22 °C lower than the onset for neat cPPA alone in dynamic thermogravimetric analysis experiments. Increased concentrations of PVtBCS increase the rate of depolymerization of cPPA. Raman spectroscopy reveals that the monomer, o-phthalaldehyde, is the main depolymerization product of the acid-catalyzed depolymerization of cPPA. The PVtBCS/cPPA blend is a promising material for the design and manufacture of transient electronic packaging and polymers.

Cyclic Poly(phthalaldehyde): Thermoforming a Bulk Transient Material.

Cyclic poly(phthalaldehyde) (cPPA) is a metastable and stimuli responsive polymer that undergoes rapid solid state depolymerization and has been utilized as a packaging and encapsulating material for transient applications. However, the early onset thermal depolymerization of cPPA severely hinders the fabrication and processing of plastic parts. Herein, the thermally triggered depolymerization of cPPA was investigated and tailored to enable thermal processing and molding of cPPA at moderate temperatures below the thermal depolymerization temperature. Stabilization of cPPA at elevated temperature was accomplished by removal of the latent Lewis acid catalyst BF3 and by addition of radical inhibitors and a Lewis base. Addition of a plasticizer to the stabilized cPPA enabled the fabrication of a monolithic solid polymer via hot press molding. Importantly, it is shown that the thermally processed cPPA retains its stimuli responsive depolymerization capability and will enable future work in the fabrication of bulk plastic parts that depolymerize and disintegrate on demand.

A Quantitative Relationship between Signal Detection in Attention and Approach/Avoidance Behavior.

This study examines how the domains of reward and attention, which are often studied as independent processes, in fact interact at a systems level. We operationalize divided attention with a continuous performance task and variables from signal detection theory (SDT), and reward/aversion with a keypress task measuring approach/avoidance in the framework of relative preference theory (RPT). Independent experiments with the same subjects showed a significant association between one SDT and two RPT variables, visualized as a three-dimensional structure. Holding one of these three variables constant, further showed a significant relationship between a loss aversion-like metric from the approach/avoidance task, and the response bias observed during the divided attention task. These results indicate that a more liberal response bias under signal detection (i.e., a higher tolerance for noise, resulting in a greater proportion of false alarms) is associated with higher "loss aversion." Furthermore, our functional model suggests a mechanism for processing constraints with divided attention and reward/aversion. Together, our results argue for a systematic relationship between divided attention and reward/aversion processing in humans.