Insights into the Deactivation of Neutral Nickel Ethylene Polymerization Catalysts in the Presence of Functionalized Olefins

A study on the products of reaction between a neutral nickel(II) olefin polymerization catalyst and methyl acrylate is presented. A deactivation mechanism involving hydrogen transfer from substrate to catalyst is suggested

Kinetic Rates of Thermal Transformations and Diffusion in Polymer Systems Measured during Sub-millisecond Laser-Induced Heating

Probing chemical reaction kinetics in the near-solid state (small molecules and polymers) is extremely challenging because of the restricted mobility of reactant species, the absence of suitable analytical probes, and most critically the limited temperature stability of the materials. By limiting temperature exposure to extremely short time frames (sub-millisecond), temperatures in excess of 800 °C can be accessed extending kinetic rate measurements many orders of magnitude. Here we demonstrate measurements on a model system, exploiting the advantages of thin-films, laser heating, and chemically amplified resists as an exquisite probe of chemical kinetic rates. Chemical reaction and acid diffusion rates were measured over 10 orders of magnitude, exposing unexpected and large changes in dynamics linked to critical mechanism shifts across temperature regimes. This new approach to the study of kinetics in near-solid state materials promises to substantially improve our understanding of processes active in a broad range of temperature-sensitive, low-mobility materials

Fluorinated Acid Amplifiers for EUV Lithography

Fluorinated Acid Amplifiers for EUV Lithograph

Neutral Nickel(II)-Based Catalysts for Ethylene Polymerization

Neutral salicylaldiminato Ni(II) complexes have been synthesized, and their structure has been confirmed by an X-ray analysis of complex 4e. These compounds are active catalysts for the polymerization of ethylene under mild conditions in the presence of a phosphine scavenger such as Ni(COD)2 or B(C6F5)3

Behavior of Lamellar Forming Block Copolymers under Nanoconfinement: Implications for Topography Directed Self-Assembly of Sub-10 nm Structures

Directed self-assembly of block copolymers (BCPs) is a promising technique for the nanofabrication of structures with dimensions smaller than what can be achieved by current photolithography approaches. In particular, there has been significant interest in the development of BCPs that can achieve ever smaller feature sizes with low levels of defects. Here we investigate the directed self-assembly of a high-χ BCP, polystyrene-<i>block</i>-poly­(dl-lactide), which is capable of producing structures with dimensions less than 10 nm. In addition, we study the behavior of the BCP under nanoconfinement and the ability of the polymer chains to compress and stretch in response to the geometry of the confining volume. Key findings of this study are that the level of defects in the self-assembled structures are strongly related to the relative interfacial interactions of the BCP as well as the degree of frustration of the polymer chains under nanoconfinement relative to the bulk. These results have particular significance for nanofabrication of ordered structures, which is of relevance for the fabrication of nanowires, metamaterials, and next-generation computer chips

Tuning the Kinetics and Energetics of Diels−Alder Cycloaddition Reactions to Improve Poling Efficiency and Thermal Stability of High-Temperature Cross-Linked Electro-Optic Polymers

A comprehensive theoretical and experimental study of the bromo effect on Diels−Alder (DA) and retro-Diels−Alder (rDA) reactions between the anthracene-containing dienes and maleimide dienophile has been conducted to improve thermal stability and poling efficiency of electro-optic (EO) polymers. Calculations with density functional theory (DFT) reveal that the bromo substitution on anthracene-based dienes leads to significantly increased cycloaddition exothermicities (9−12 kcal/mol) but has a minor effect on their activation barriers (0.6−3 kcal/mol) when reacted with N-phenylmaleimide dienophile. These calculated values correlate very well with the experimental results obtained from a series of model compounds. The DA/rDA cross-linking protocols based on these compounds can be applied to several nonlinear optical (NLO) polymers and result in large EO coefficients (r33) (as high as 69 pm/V) and greatly improved thermal stability (up to 250 °C). This demonstrates that controlled DA/rDA reactions can be used to improve the performance of EO polymers for chip-scale interconnects that requires very high thermal stability