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Kinetic Modeling Of Slurry Propylene Polymerization Using Rac-Et(Ind)2zrcl2/Mao, Ramon A. Gonzalez-Ruiz, Bernabe Quevedo-Sanchez, Robert L. Laurence, Michael A. Henson, E. Bryan Coughlin
Kinetic Modeling Of Slurry Propylene Polymerization Using Rac-Et(Ind)2zrcl2/Mao, Ramon A. Gonzalez-Ruiz, Bernabe Quevedo-Sanchez, Robert L. Laurence, Michael A. Henson, E. Bryan Coughlin
Michael A Henson
The slurry homopolymerization of propylene catalyzed by the isospecific metallocene rac-Et(Ind)2ZrCl2/MAO was investigated using a semi-batch reactor. A full factorial design with three temperatures (50, 65 and 75°C) and four monomer partial pressure (1.5, 2.5, 3.2, and 3.8 atm) was performed. Analysis by 1H NMR revealed the formation of vinylidene, cis-2-butenyl and 4-butenyl end-groups. A kinetic model based on a coordination-insertion mechanism was developed to predict instantaneous reaction rate, molecular weights and polymer chain ends. The kinetic rate constants were estimated using a systematic optimization strategy. The model predicts that the insertion of the first propylene molecule is rate limiting …
Origin Of The Formation Of The 4-Butenyl End Group In Zirconocene-Catalyzed Propylene Polymerization, Bernabe Quevedo-Sanchez, Michael A. Henson, E. Bryan Coughlin
Origin Of The Formation Of The 4-Butenyl End Group In Zirconocene-Catalyzed Propylene Polymerization, Bernabe Quevedo-Sanchez, Michael A. Henson, E. Bryan Coughlin
Michael A Henson
It has been proposed that the 4-butenyl end group in polypropylene is formed by isomerization of the 2-butenyl end group. Prior experimental evidence has shown that the isomerization is not produced thermally or upon an acidic treatment during the workup or analysis of the polymer. We postulate that the production of the 4-butenyl end group by isomerization might be catalyzed by a zirconocene hydride complex that forms during the β-hydride elimination reaction. The isomerization of a preformed olefinic-end-group isotactic polypropylene with a well-known transition-metal hydride shows the disappearance of the 2-butenyl end group concomitant with the appearance of the 4-butenyl …
Transient Dynamics And Structure Of Optimal Excitations In Thermocapillary Spreading: Precursor Film Model, Jm Davis, De Kataoka, Sm Troian
Transient Dynamics And Structure Of Optimal Excitations In Thermocapillary Spreading: Precursor Film Model, Jm Davis, De Kataoka, Sm Troian
Jeffrey M. Davis
Linearized modal stability theory has shown that the thermocapillary spreading of a liquid film on a homogeneous, completely wetting surface can produce a rivulet instability at the advancing front due to formation of a capillary ridge. Mechanisms that drain fluid from the ridge can stabilize the flow against rivulet formation. Numerical predictions from this analysis for the film speed, shape, and most unstable wavelength agree remarkably well with experimental measurements even though the linearized disturbance operator is non-normal, which allows transient growth of perturbations. Our previous studies using a more generalized nonmodal stability analysis for contact lines models describing partially …
Synthesis Of Transportation Fuels From Biomass: Chemistry, Catalysts, And Engineering, George W. Huber, S. Iborra, A. Corma
Synthesis Of Transportation Fuels From Biomass: Chemistry, Catalysts, And Engineering, George W. Huber, S. Iborra, A. Corma
George W. Huber
No abstract provided.
Theoretical Analysis Of The Effect Of Insoluble Surfactant On The Dip Coating Of Chemically Micropatterned Surfaces, N Tiwari, Jm Davis
Theoretical Analysis Of The Effect Of Insoluble Surfactant On The Dip Coating Of Chemically Micropatterned Surfaces, N Tiwari, Jm Davis
Jeffrey M. Davis
Microfluidic flow on chemically heterogeneous surfaces is a useful technique with applications ranging from selective material deposition to the self-assembly of nanostructures. The recent theoretical analysis by Davis [Phys. Fluids 17, 038101 (2005)] of the dip coating of a pure fluid onto vertical, wetting stripes surrounded by nonwetting regions quantified the experimentally observed deviations from the classical Landau-Levich result due to lateral confinement of the fluid by chemical surface patterning. In this present work, the analysis of dip coating of these heterogeneous surfaces is extended to a liquid containing an insoluble surfactant. Using matched asymptotic expansions based on lubrication theory …
Wetting Of Rings On A Nanopatterned Surface: A Lattice Model Study, Peter A. Monson, Fabien Porcheron
Wetting Of Rings On A Nanopatterned Surface: A Lattice Model Study, Peter A. Monson, Fabien Porcheron
Peter A. Monson
We perform mean-field density functional theory calculations on a lattice model to study the wetting of a solid substrate decorated with a ring pattern of nanoscale dimensions. We have found three different liquid morphologies on the substrate: a ring morphology where the liquid covers the pattern, a bulge morphology where a droplet is forming on one side of the ring, and a morphology where the liquid forms a cap spanning the nonwetting disk inside the pattern. We investigate the relative stability of these morphologies as a function of the ring size, wall-fluid interaction, and temperature. The results found are in …
Lyotropic Columnar Liquid Crystals Based On Polycatenar 1h-Imidazole Amphiphiles And Their Assembly Into Bundles At The Surface Of Silicon, Sang Hyuk Seo, Gregory N. Tew, Ji Young Chang
Lyotropic Columnar Liquid Crystals Based On Polycatenar 1h-Imidazole Amphiphiles And Their Assembly Into Bundles At The Surface Of Silicon, Sang Hyuk Seo, Gregory N. Tew, Ji Young Chang
Gregory N. Tew
Polycatenar 1H-imidazole amphiphiles, consisting of a 1H-imidazole head connected through a benzene ring to a trialkyloxyphenyl tail, were synthesized and their self-assembling properties investigated. The 1H NMR and fluorescence spectroscopy studies showed that in nonpolar solvents, the amphiphiles formed reverse micelles in which the hydrophilic imidazole heads aggregated inside the micelles through intermolecular hydrogen bonding and the nonpolar alkyl chains were located at the periphery of the micelles. In concentrated solutions, they formed lyotropic liquid crystals having columnar hexagonal structures. The molecules were arranged in a disk via hydrogen bonding between successive imidazole moieties. When dilute solutions of the amphiphiles …