Fourier-transform infrared study of coextrusion-drawn poly(ethylene terephthalate)

The effects of initial morphology and extrusion temperature on the orientational anisotropy and conformational changes on coextrusion drawing of poly(ethylene terephthalate) (PET) have been determined by Fourier-transform polarized infrared spectroscopy. The samples were drawn from both amorphous and semicrystalline (50%) PET at 50 and 90°C. A strong influence of coextrusion drawing temperature was observed for overall chain orientation evaluated from the dichroic ratio of the 795-cm^?1 band for the samples prepared from the amorphous state: this dependence was less prominent in samples drawn from the semicrystalline state. Under the same drawing conditions, the dichroic ratio for the 973-cm^?1 trans band for samples prepared from the amorphous state was higher than from the semicrystalline state. Furthermore, in all samples, the relative intensity of this band was almost proportional to the degree of crystallinity. In all samples, the gauche content, evaluated from the 896-cm^?1 band, decreased with increasing draw ratio. However, the dichroic ratio of this band was near unity regardless of draw ratio, initial morphology, or extrusion temperature. From these results it is considered that all gauche units in the amorphous phase are almost isotropic in the extrusion-drawn samples with overall orientation arising largely from the crystalline chains possessing totally the trans conformation (973 cm^?1) in its content. In order to evaluate the deformation mechanism of the coextrusion drawing method, the relationship between the bulk and film surface orientation is also reported.     

Estimation of heterogeneous surface structure of submicron-sized,composite polymer particles consisting of hydrophobic and hydrophilic components by atomic force microscopy*

Surface structure of submicron-sized poly(styrene/2-hydroxyethyl methacrylate) [P(S/HEMA)] composite particles produced by emulsifier-free emulsion polymerization was estimated with atomic force microscopy (AFM). AFM force curves were measured in water at different points of the particle surface; it was clarified that the particle surface had a heterogeneous structure consisting of hard and soft parts, which must be, respectively, based on styrene-rich and 2-hydroxyethyl methacrylate-rich parts.     

Studies of the polymerization of diallyl compounds. XXXVII. Copolymerizations of diallyl phthalate with dialkyl fumarates

Diallyl phthalate (DAP) was copolymerized with dialkyl fumarates, including diethyl fumarate (DEF), di-n-butyl fumarate (DBF), and di-n-octyl fumarate (DOF) by using 2,2′-azobisisobutyronitrile as an initiator at 60°C. Both rate and degree of copolymerization were quite enhanced compared with the homopolymerization of DAP and the maximum rate was found at the molar ratio of 1:1 in the monomer feed. The cyclization of DAP was almost exclusively suppressed in the Copolymerization. Gelation was promoted from 25% of the gel-point conversion for the DAP homopolymerization to 9% of the minimum one observed. Copolymerizability of DAP (M₁) with dialkyl fumarates (M₂) was quite high, with the following monomer reactivity ratios M₂, r₁, r₂: DEF, 0.01, 1.25; DBF, 0.02, 1.01; DOF, 0.02, 0.96. These results are discussed in mechanistic detail.     

A kinetic method for the determination of zinc(II) in presence of a large excess of cadmium(II) by the different dissociation rate of their complexes with 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine

Summary Acid-dissociation reaction of the cadmium(II) complex of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphme (H₂tspp) proceeds about 10¹² times as fast as that of the zinc(II) complex. This provides the basis for a kinetic determination of zinc(II) in presence of a large excess of cadmium (II). The absorbance at soret-band (421 nm) of Zn(II)(tspp) was used to monitor the reaction. At 5.0×10^–2 M hydrogen ion concentration, Cd(II)(tspp) dissociates completely to Cd²⁺ in 1 s and only the reaction associated with Zn(II)(tspp) is observed during the reaction time from 30 s to 5 min. Zinc(II) concentration <10^–6 M is determined in the presence of 10^–2 M cadmium(II). The molar absorption coefficient is 2.7×10⁵ M ^–1 cm^–1. Iron(III), aluminum(III) and cobalt(II) being masked sodium tartrate, this method is highly selective and is free from interferences of most substances usually encountered. The method was applied to determine zinc(II) in tap water and in cadmium(II) sulfate.     

Time-resolved investigation of the de-excitation of xenon excimer by SF6 and N2 excited with synchrotron radiation

An attempt has been made 'o measure the rate constant for the de-excitation of a state-specified excimer using the pulse character of synchrotron radiation. The rate constants have been obtained for de-excitation of a vibrationally relaxed excimer Xe₂^*(O_u⁺; low v) by SF₆ and N₂ as 9 × 10^?10 and 7 × 10^?12 cm³ molecule^?1 s^?1 respectively.     

Control of stepwise radial complexation in dendritic polyphenylazomethines

The fourth generation of a dendritic polyphenylazomethine (DPA G4) has 2, 4, 8, and 16 imine groups in the first, second, third, and fourth shells, respectively (total, 30 imine groups). DPA G4 can trap 30 equiv of SnCl(2) molecules, because the imine group is complexed with SnCl(2) at a ratio of 1:1. During addition of 30 equiv of SnCl(2) to DPA G4, four shifts in the isosbestic point were observed in the UV-vis spectra, and the amount of SnCl(2) added in each step is in agreement with the number of imine groups in each shell of DPA G4. This result shows that the complexation of the imine groups in DPA G4 with SnCl(2) occurs stepwise in the order of the first, second, third, and fourth shells. The unique stepwise complexation was also observed in DPA G2 and G3 as two and three shifts of the isosbestic point, respectively. The stepwise complexation was supported by TEM, NMR, and a novel shell-selective reduction (SSR) method for imines. An expansion in the molecular size of DPA G4 by the complexation was revealed by molecular modeling and TEM measurements. The stepwise complexation is caused by the different basicity of the imine groups between the shells, which was supported by the chemical shifts of the peaks attributed to the imine carbons in the (13)C NMR spectra. The gradients in the basicity were controlled by the introduction of electron-withdrawing or -releasing groups to the core of the dendrimers; the core imines were complexed last in DPAs having a 2,3,5,6-tetrafluoro or 2,5-dichlorophenyl core due to the low basicity of the core imines. The different complexation pattern was also clearly confirmed by the SSR method.     

Stereoselective construction of a beta-isopropenyl alcohol moiety at the C(2) and (3) of kallolide A and pinnatin a using a [2,3] Wittig rearrangement of cyclic furfuryl ethers

A stereocontrolled synthesis of anti- and syn-beta-isopropenyl alcohol moieties at the C(2)-C(3) positions of kallolide A and pinnatin A was accomplished employing the [2,3] Wittig rearrangement of (E)-and (Z)-cyclic furfuryl ethers 8. Enantioselective Wittig rearrangement of (E)- and (Z)-furfuryl ethers 8 using butyllithium and a chiral bis(oxazoline) was also examined to provide (2R,3R)-homoallylic alcohol anti-9 in up to 61% ee and (2R,3S)-syn-9 in up to 93% ee, respectively.     

Condensed thienopyrimidines. I. Synthesis and gastric antisecretory activity of 2,3-dihydro-5H-oxazolothienopyrimidin-5-one derivatives

A practical preparation of various 2,3-dihydro-5H-oxazolo[3,2-a]thieno[3,2-d]-, [3,4-d]-, and [2,3-d]pyrimidin-5-one derivatives was developed starting from the corresponding aminothiopheneesters in two steps, and their chloro-substituted derivatives were prepared. These compounds were evaluated for gastric antisecretory activity in pylorus-ligated rats, compared to the anti-ulcer standard, cimetidine, and their structure-activity relationships are discussed.