David D. Devore

Titanium (II) or Zirconium (II) complexes and addition polymerization catalysts therefrom

Novel titanium or zirconium complexes containing one and only one cyclic delocalized, anionic, π-bonded group wherein the metal is in the +2 formal oxidation state and having a bridged ligand structure, also referred to as constrained geometry complexes; catalytic derivatives of such complexes; methods of preparation; and the use thereof as catalysts for polymerizing olefins, diolefins and/or acetylenically unsaturated monomers.

Polymer-bound hindered amine light stabilizers for improved weatherability in multi-phase polymer systems

Abstract Hindered amine light stabilizers (HALS) have been bound to both the rubber and matrix phases of acrylonitrile-EPDM-styrene (AES) terpolymers. The stabilizers were incorporated by reaction of either 4-aminotetramethylpiperidine or 4-aminooxamidetetramethylpiperidine with anhydride functionality incorporated into the EPDM or SAN. This method permits control of the phase location of the stabilizers in multi-phase polymer systems. Thereby the phase most susceptible to degradation can be positively stabilized. The polymers were evaluated via accelerated weathering. These studies show that the primary function of HALS in AES is to inhibit degradation of the EPDM rubber phase. Superior weathering performance results when HALS is both bound to the rubber phase and melt blended into the product.

Molecular orientation, thermal behavior and density of electron and hole transport layers and the implication on device performance for OLEDs

Recent progress has shown that molecular orientation in vapor-deposited glasses can affect device performance. The deposition process can result in films where the molecular axis of the glass material is preferentially ordered to lie parallel to the plane of the substrate. Here, materials made within Dow’s Electronic Materials business showed enhanced performance when the orientation of the molecules, as measured by variable angle spectroscopic ellipsometry, was oriented in a more parallel fashion as compared to other materials. For one material, the anisotropic packing was observed in the as-deposited glass and was isotropic for solution-cast and annealed films. In addition, the density of an as-deposited N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine (NPD) film was 0.8% greater than what was realized from slowly cooling the supercooled liquid. This enhanced density indicated that vapor-deposited molecules were packing more closely in addition to being anisotropic. Finally, upon heating the NPD film into the supercooled liquid state, both the density and anisotropic packing of the as-deposited glass was lost.

Impact of High Throughput Experimentation on Homogeneous Catalysis Research

As new tools and techniques have become available, the expansion of high throughput experimentation into the broader chemical community has occurred, with the application of this infrastructure moving beyond biologically focused research and into the mainstream of materials and catalytic research. The study of homogeneous catalysis has been significantly impacted by the application of high throughput research. For research problems where the number of variables are very high, these tools are ideally suited to significantly increase the experimental output and speed the time for discovery and development of new catalysts and catalytic applications. In addition, high throughput experimentation provides for an opportunity to conduct a much more diverse structure activity study of new catalyst families and, with the greater experimental throughput, allows researchers to explore more “out of the box” solutions. In this Comment, the impact of homogeneous catalysis high throughput research at The Dow Chemical Company and in the broader catalysis community will be reviewed and examples of high throughput research towards the major areas in this field will be highlighted.

Resolving and Controlling Photoinduced Ultrafast Solvation in the Solid State

Solid-state solvation (SSS) is a solid-state analogue of solvent-solute interactions in the liquid state. Although it could enable exceptionally fine control over the energetic properties of solid-state devices, its molecular mechanisms have remained largely unexplored. We use ultrafast transient absorption and optical Kerr effect spectroscopies to independently track and correlate both the excited-state dynamics of an organic emitter and the polarization anisotropy relaxation of a small polar dopant embedded in an amorphous polystyrene matrix. The results demonstrate that the dopants are able to rotationally reorient on ultrafast time scales following light-induced changes in the electronic configuration of the emitter, minimizing the system energy. The solid-state dopant-emitter dynamics are intrinsically analogous to liquid-state solvent-solute interactions. In addition, tuning the dopant/polymer pore ratio offers control over solvation dynamics by exploiting molecular-scale confinement of the dopants by the polymer matrix. Our findings will enable refined strategies for tuning optoelectronic material properties using SSS and offer new strategies to investigate mobility and disorder in heterogeneous solid and glassy materials.

Degradation of Hole Transport Materials via Exciton-Driven Cyclization

Organic light-emitting diode (OLED) displays have been an active and intense area of research for well over a decade and have now reached commercial success for displays from cell phones to large format televisions. A more thorough understanding of the many different potential degradation modes which cause OLED device failure will be necessary to develop the next generation of OLED materials, improve device lifetime, and to ultimately improve the cost vs performance ratio. Each of the different organic layers in an OLED device can be susceptible to unique decomposition pathways, however stability toward excitons is critical for emissive layer (EML) materials as well as any layer near the recombination zone. This study will specifically focus on degradation modes within the hole transport layer (HTL) with the goal being to identify the general decomposition paths occurring in an operating device and use this information to design new derivatives which can block these pathways. Through post-mortem analyses of several aged OLED devices, an apparently common intramolecular cyclization pathway has been identified that was not previously reported for arylamine-containing HTL materials and that operates parallel to but faster than the previously described fragmentation pathways.