An ab initio and force field study on the conformation and chain flexibility of the dichlorophosphazene trimer

Ab initio molecular orbital calculations have been used to study the conformation, valence electron charge density, and chain flexibility of a dichlorophosphazene trimer (CH3[NP(Cl2)]3CH3). The calculations were carried out at the restricted Hartree-Fock level with the 6-31 G* basis set. The dichlorophosphazene trimer adopts a planar transcis conformation. The valence electron charge distribution indicates strong charge separations along the backbone of the molecule, and is in agreement with Dewar's island delocalization model for bonding in linear and cyclic phosphazenes. In order to determine the height of the torsional barrier (2,5 kcal/mol), the torsional potential of a central P-N bond of the trimer was studied with a rigid rotor scan and geometry optimizations of selected rotamers. The flexibility of the P-N-P bond angle contributes significantly to the chain flexibility. Based on the results of the ab initio calculations, an empirical force field for the dichlorophosphazene trimer was developed. The energy expression includes bond stretch, angle bend, electrostatic, van der Waals, and torsional potential terms. A relaxed scan with the force field achieves good agreement with the ab initio results for the torsional potential in the vicinity of the stable conformation, and an excellent agreement with the ab initio results on changes in the P2N2P3 bond angle and the N1P2 - N2P3 dihedral angle during a full rotation around the N2 - P3 bond

Einlegesohle und Verfahren zu deren Herstellung

DE102013224142A1 [DE] Die Erfindung betrifft eine Einlegesohle (1) mit einer an die Fussform des Benutzers angepassten Form, welche zumindest ein Polymermaterial enthaelt oder aus zumindest einem Polymermaterial hergestellt ist, wobei das Polymermaterial Poren (251) enthaelt, welche eine geometrisch definierte Anordnung aufweisen. Weiterhin betrifft die Erfindung ein Verfahren zur Herstellung einer Einlegesohle

Ab initio study of the structure of poly[di(phenoxy)thionylphosphazene]

The stable structure of poly[(diphenoxy)thionylphosphazene] single chains was modeled with a small molecular compound consisting of one repeat unit of the polymer. The geometrical parameters of the nonplanar “trans-cis” conformations of these molecular models were obtained using the ab initio molecular orbital theory. The 3-21G∗ basis set was used in the computation. It was found that the phenoxy groups are positioned approximately parallel to the backbone and the groups located on adjacent phosphorus atoms point in opposite directions. The bonding of the short chain segment exhibits a “single-double” alternating pattern along the backbone. The charge distribution along the backbone is highly polarized. The total dipole moment is oriented parallel to the backbone and is equal to 6.75 debye. The molecular diameter of this compound is estimated to be 13 Å

Ab initio studies on the structure, conformation, and chain flexibility of halogenated poly(thionylphosphazenes)

Ab initio quantum chemical calculations on short-chain model compounds have been used to study the conformation, valence electron density, and chain flexibility of halogen-substituted poly-(thionylphosphazenes) (PTPs) [(NSOX)(NPCl&], (X = F or Cl), which are representatives of a new class of inorganic sulfur(vI)-nitrogen-phosphorus polymers. The calculations were carried out at the closedshell Hartree-Fock level of theory using the Gaussian 92 program package. The electronic wave function was described by the 6-31G* basis set. The results show that model compounds adopt a nonplanar transcis conformation in the minimum-energy state. Based on the stable geometries of the short-chain analogues, the polymer will form a 12/5 helix in its extended conformation. Rigid rotor scans and geometry optimizations of selected rotamers were used in order to investigate the torsional mobility of the main chain of the model compounds. The flexibility of the S-N-P and P-N-P bond angles contributes significantly to the chain flexibility. The torsional barriers for rotations around bonds of the PTP backbone range from 1.5 to 3.5 kcal/mol. A change from chlorine to fluorine as a substituent on sulfur leads to lower torsional barriers and wider minima of the rotational potentials and therefore to an increased torsional mobility of the main chain. The increase in chain flexibility is consistent with trends in glass transition temperatures of the corresponding polymers. The electronic structure of the model compounds, including charge density distributions, is briefly discussed. The results indicate strong charge separations along the backbone of the polymer and in the direction of the substituents bonded to the main chain which are consistent with Dewar’s island delocalization model

Wear resistant all-PE single-component composites via 1D nanostructure formation during melt processing

Melt-flow-induced crystallization of polyethylene blends having tailored ultrabroad molar mass distribution affords extended-chain ultrahigh molar mass (UHMWPE) nanophases resembling nanofibers which effectively reinforce the polyethylene matrix. Unparalleled by state-of-the-art high density polyethylene (HDPE), the resulting melt-processable all-polyethylene single component composites exhibit simultaneously improved wear resistance, toughness, stiffness and strength. Key intermediates are trimodal blends prepared by melt compounding HDPE with bimodal UHMWPE/HDPE wax reactor blends (RB) readily tailored by ethylene polymerization on supported two-site catalysts. Whereas HDPE wax, varied up to 54 wt.-%, serves as processing aid lowering melt viscosity, UHMWPE varied up to 63 wt.-% accounts for improved blend properties. UHMWPE platelet-like nanophase separate during ethylene polymerization and readily melt during injection molding of RB/HDPE blends producing extended-chain fiber-like UHMWPE nanostructures of 100 nm diameter as shish which nucleate HDPE and HDPE wax crystallization to form shish-kebab-like structures. At 32 wt.-% UHMWPE content shish-kebab-like reinforcing phases account for massive polyethylene self-reinforcement as reflected by improved Young's modulus (+420%), tensile strength (+740%) and notched Izod impact strength (+650%) without impairing HDPE injection molding. All-PE composites exhibit high wear resistance entering ranges typical for polyamide and monomodal UHMWPE which is not processable by injection molding under identical conditions