Lorentz Boosted Potential for a Two-Body System with Unequal Masses

We produce a Lorentz boosted two-body potential for particles of different mass that is phase equivalent to a given realistic non-relativistic two-body potential. The relativistic potential is related to the nonrelativistic potential using the Coester–Pieper–Serduke scheme, which ensures that the same scattering wave functions are obtained from the relativistic and non-relativistic potentials. This implies that the phase shifts are identical functions of the relative momentum. To construct the potential we use an iterative scheme that generalizes one that has been applied successfully to two-body systems with equal masses.     

Preparation and Thermal Decomposition of Cyclic Azoamidinium Salts as Water-Soluble Radical Initiators for Polymerization over A Wide Temperature Range

Abstract

A series of cyclic azoamidinium chlorides as water-soluble initiators were prepared by reactions of the iminoether derived from 2,2′-azobisisobutyronitrile with substituted alkylene diamines. The first-order rate constants for the decomposition of the azoamidinium salts varied from 0.59 × 10^?5 to 14.1 × 10^?5 s^?1 with the ring size and the alkyl substitution of the ring. Decomposition of 2,2′-azobis[2-(imidazoline-2-yl)propane] dihydrochloride was found to be accelerated by alkyl substitution on the imidazolinium ring. However, the azoamidinium compounds having larger rings, 2,2′-azobis[2-(3,4,5-trihydropyrimi-dine-2-yl)propane] dihydrochloride and 2,2′-azobis[2-(4,5,6,7-tetra-hydro-1H-1,3-diazepine-2-yl)propane] dihydrochloride, decomposed at a slower rate than the unsubstituted azobis[2-(imidazoline-2-yl)-propane] dihydrochloride. These new initiators were found to be capable of initiating radical polymerizations of acrylamide and vinyl acetate.     

Photosensitive fluorinated polyimides with a low dielectric constant based on reaction development patterning

The fluorinated polyimide PI(6FDA/HFBAPP) was prepared by the reaction of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane (HFBAPP) in 1‐methyl‐2‐pyrrolidone/toluene. A multiblock copolyimide with both fluorinated and rigid‐rod segments, PI(6FDA/HFBAPP)(BPDA/2‐DMB), was prepared by the addition of a second dianhydride, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), and a second diamine, 2,2′‐dimethylbenzidine (2‐DMB), to the polyimide main chain. The potential lithographic performance of photosensitive polyimides composed of nonphotosensitive fluorine‐containing polyimides and photosensitive diazonaphthoquinone (DNQ) was studied on the basis of a new imaging principle recently proposed by our laboratory, that is, reaction development patterning. Neat PI(6FDA/HFBAPP) showed a low dielectric constant (?) of 2.41 and a low dissipation factor (tan δ) of 0.0027 at 20 GHz, and a 10‐μm resolution of the fluorinated polyimide/DNQ system was demonstrated with reactive development with a solution including ethanolamine after ultraviolet exposure. Although slight changes in the dielectric properties were observed in the presence of DNQ residues, these values (? = 2.63 and tan δ = 0.0033 at 20 GHz) were low enough for use in microelectronic applications. However, PI(6FDA/HFBAPP)(BPDA/2‐DMB), having a lower coefficient of thermal expansion (CTE; 33 ppm/°C) than PI(6FDA/HFBAPP) (49 ppm/°C), exhibited good positive photosensitivity, whereas the relatively low‐CTE multiblock copolyimide displayed a much higher ? value (3.48 at 1 MHz) than the highly fluorinated polyimide (2.88 at 1 MHz). A film consisting of PI(6FDA/HFBAPP)(BPDA/2‐DMB) and the remaining DNQ derivatives showed a CTE value comparable to that of the neat polyimide film. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 861–871, 2003     

Photo‐alignment material with azobenzene‐functionalized polymer linked in film

Application of a new azo‐polymer as a photo‐alignment material for liquid crystals (LCs) was demonstrated. 4‐(Vinyloxyethyloxy)azobenzene (VAZO), which has thermally reactive vinyl ether groups, reacted with the ? OH groups of poly(4‐hydroxystyrene) (PHS) during the baking process. The azo‐attached polymer (PHS‐VAZO) film showed anisotropic spectra after exposure to 365‐nm linear polarized light (LPL) unlike the VAZO‐doped poly(methylmethacrylate) (PMMA) film. The anisotropy of the film was small at high concentration of the azo‐chromophore because of thermal randomization of the polarized state. In the evaluation of photo‐alignment of the LC, the LC hybrid cell using the PHS‐VAZO film achieved high LC alignment. The azo‐attached polymer using the thermal reaction of vinyl ethers is useful for a photo‐alignment material. Copyright © 2002 John Wiley & Sons, Ltd.     

Amine‐cured epoxy/clay nanocomposites. I. Processing and chemical characterization

The processing of nanocomposite materials composed of amine‐cured diglycidyl ether of bisphenol A (DGEBA) reinforced with organomontmorillonite clay is reported. A novel sample preparation scheme was used to process the modified clay in the glassy epoxy network, resulting in nanocomposites where the clay was both exfoliated and intercalated by the epoxy network. The processing scheme involves sonication of the constituent materials in a solvent, followed by solvent extraction to generate a composite with homogeneous dispersions of the nanoclay. Fourier transform infrared spectroscopy (FTIR) and Fourier transform (FT‐)Raman spectroscopy confirmed that the chemical structure of the epoxy network was not affected by the use of solvents in this processing scheme. The glass‐transition temperature, T_g, linearly increased with an increased weight ratio of the nanoclay. The microstructure of clay nanoplatelets in the composites was observed with transmission electron microscopy (TEM), wide‐angle X‐ray scattering (WAXS), and small‐angle X‐ray scattering (SAXS). It was found that the clay nanoplatelets were well‐dispersed, and were intercalated as well as exfoliated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4384–4390, 2004     

A Five‐layer π‐Aromatic Structure Formed through Self‐assembly of a Porphyrin Trimer and Two Aromatic Guests

In this study we synthesized two‐ and four‐armed porphyrins – bearing two carboxyl and four 2‐aminoquinolino functionalities, respectively, at their meso positions – as a complementary hydrogen bonding pair for the self‐assembly of a D₂‐symmetric porphyrin trimer host. Two units of the two‐armed porphyrin and one unit of the four‐armed porphyrin self‐assembled quantitatively into the D₂‐symmetric porphyrin trimer, stabilized through ammidinium‐carboxylate salt bridge formation, in CH₂Cl₂ and CHCl₃. The porphyrin trimer host gradually bound two units of 1,3,5‐trinitrobenzene between the pair of porphyrin units, forming a five‐layer aromatic structure. At temperatures below ?40 °C, the rates of association and dissociation of the complexes were slow on the NMR spectroscopic time scale, allowing the 1 : 1 and 1 : 2 complexes of the trimer host and trinitrobenzene guest(s) to be detected independently when using less than 2 eq of trinitrobenzene. Vis titration experiments revealed the values of K₁ (2.1±0.4×10⁵ M^?1) and K₂ (2.2±0.06×10⁴ M^?1) in CHCl₃ at room temperature.     

Equilibrium Shift in Solution: Molecular Shape Recognition and Precipitation of a Synthetic Double Helix Using Helicene‐Grafted Silica Nanoparticles

Chiral silica nanoparticles (70 nm) grafted with (P)‐helicene recognized the molecular shape of double helix and random coil (P)‐ethynylhelicene oligomers in solution. A mixture of the (P)‐nanoparticles and double helix precipitated much faster than a mixture of the (P)‐nanoparticles and random coil, and the precipitate contained only the double helix. The mixture of the (P)‐nanoparticles and (P)‐ethynylhelicene pentamer reversibly dispersed in trifluoromethylbenzene upon heating at 70 °C and precipitated upon cooling at 25 °C. When a 10:90 equilibrium mixture of the double helix and random coil in solution was treated with the (P)‐nanoparticles, the double helix was precipitated in 53 % yield and was accompanied by equilibrium shift.     

Novel biobased resins from blends of functionalized soybean oil and unsaturated polyester resin

Biobased unsaturated polyester (UPE) materials containing epoxidized methyl soyate (EMS) were processed with cobalt naphthenate as a promoter and 2‐butanone peroxide as an initiator. A certain amount of the UPE resin was replaced by EMS. The combination of the UPE and EMS resulted in an excellent combination for a new biobased thermoset material with a relatively high elastic modulus and a constant glass transition temperature with up to 25 wt % replacement with EMS. The Izod impact strength was almost constant while the amount of EMS was changed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 698–704, 2007