Living cationic polymerization of isobutyl vinyl ether initiated by the trimethylsilyl iodide/zinc iodide system

Summary Trimethylsilyl iodide in conjunction with zinc iodide (Me₃SiI/ZnI₂) as an initiating system led to living cationic polymerization of isobutyl vinyl ether in toluene at 0 or –40°C or in methylene chloride at –40°C (ZnI₂ was dissolved in acetone). The number-average molecular weight of the polymers was directly proportional to monomer conversion and in excellent agreement with the calculated value assuming that one polymer chain forms per unit trimethylsilyl iodide. At room temperature (+25°C), however, the polymerization failed to give perfectly living polymers; the polymer molecular weight was smaller than the calculated value. On addition of a fresh feed of monomer at the end of the polymerization at –40°C, the added feed was smoothly polymerized at nearly the same rate as in the first stage, and the polymer molecular weight continued to increase in direct proportion to monomer conversion. Throughout the reaction, the molecular weight distribution of the polymers stayed very narrow (M_w/M_n< 1.1).Living cationic polymerization of vinyl ethers by electrophile/Lewis acid initiating systems, part 2. For part 1 see ref. 2     

Preparation and surface- active properties of new amphipathic compounds with two phosphate groups and two long- chain alkyl groups

New compounds bearing two dihydrogen phosphate groups and two long- chain alkyl groups (octyl or decyl) were prepared in good yields by the reaction of 1,ω-bis(alkyloxymethyl)- oligo (ethylene glycol)s with polyphosphoric acid. Amphipathic di- or tetrasodium phosphates were obtained by neutralization of the free acids with sodium hydroxide, and their surface- active properties in water were measured. Almost all these di- or tetrasodium phosphates showed good water solubility. Their abilities to form micelles and to lower surface tension were fairly good as compared with general monoalkyl phosphates consisting of one longer alkyl chain and one hydrophilic group. The foaming property of aqueous solutions of the tetrasodium salts was different from that of the disodium salts. The former showed very low foaming ability.     

Synthesis of cationic surfactants with alkenyl group

Quaternary ammonium chlorides with long chain alkenyl groups were synthesized by the reaction of tert-amines with alkylallyl chloride which, in turn, were obtained by the allylic chlorination of 1-olefins with N-tert-butyl- or N-cyclohexyl-N-chloro-ethanesulfonamides. Of the two kinds of alkylallyl chlorides prepared by the allylic chlorination of 1-olefins, the γ-alkylallyl chlorides(I), were found to be reactive with tert-amines, while the secondary chlorides, α-alkylallyl chlorides(II), were not so reactive and, when the allylic chloride mixture was reacted with tert-amine under suitable reaction conditions, the γ-alkylallyl chloride could be selectively converted to a quaternary ammonium chloride while the α-alkylallyl chloride was recovered unreacted. The quaternary ammonium chlorides thus obtained were identified as γ-alkylallyl ammonium chlorides from their spectra, and they were shown to possess almost the same surface tension lowering ability as their saturated homologs, although larger critical micelle concentration values and greater water solubilities were observed.     

Dehydrogenation and hydrogenation activity of palladium-tin-silica and nickel-tin-silica

The dehydrogenation of cyclohexanone, cyclohexylamine, cyclohexane, and 2-propanol and the hydrogenation of ethylene on palladium-tin-silica and the hydrogenation of benzene on nickel-tin-silica were studied. With nickel-silica and nickel-tin-silica, the deposition of carbonaceous materials was studied kinetically. The X-ray photoelectron spectra of palladiumtin and nickel-tin were observed. The catalytic activities of both of the catalyst systems changed in similar ways with the change of the $\text{Pd}\text{Sn}$ and $\text{Ni}\text{Sn}$ ratios (atomic) of the catalysts. The dehydrogenation activity increased to a maximum and then decreased, with a decrease in the $\text{Pd}\text{Sn}$ and $\text{Ni}\text{Sn}$ ratios. The hydrogenation activity of the tin-containing catalysts was much lower than that of the tin-free catalysts. Carbonaceous materials were observed to be deposited more easily on the nickel-silica than on the nickel-tin-silica. The palladium-4d and nickel-3d band peaks of the alloy systems obtained by X-ray photoelectron spectroscopy were observed to shift to higher binding energies as the $\text{Pd}\text{Sn}$ and $\text{Ni}\text{Sn}$ ratios decreased. From the amount of carbon monoxide adsorbed, the surface concentration of palladium and that of nickel on the catalysts were suggested to be the minor determining factor of the catalytic activity studied here. It is concluded that tin is not just a diluent for the active metal but is an effective component to weaken the adsorption bond.     

Lyotropic liquid crystalline solutions of hydroxypropyl cellulose in water: Effect of salts on the turbidity and viscometric behavior

Effect of addition of salt on the viscometric behavior of the dilute or concentrated aqueous solution of hydroxypropyl cellulose (HPC) was determined by means of an Ubbelohde or a cone-plate viscometer. That effect on the turbidity of the dilute system was also determined. As salts, NaCl, LiCl, and thiourea were chosen. The turbidity and viscometric behavior for the dilute system, and the viscometric behavior for the concentrated system were greatly affected by salt type and concentration. With increasing NaCl or LiCl concentration, the cloud point decreased, [η] showed a maximum, Huggins' constant k′ showed a minimum, and the shear viscosity for concentrated isotropic solutions showed a maximum. The 45 wt % solution with no salt showed a viscometric behavior which was characteristic of lyotropic liquid crystals; however, with increasing NaCl concentration, a critical temperature at which the shear viscosity showed a maximum with respect to temperature shifted to lower temperature. This behavior was due to an increase in the turbidity, not due to a phase transformation. On the other hand, an addition of thiourea did not affect so greatly the turbidity and viscometric behavior as an addition of NaCl or LiCl did. We speculated different actions of NaCl and thiourea.     

Stress relaxation behaviour of liquid crystalline solutions of ethyl celluloses with different molecular weight in m-cresol

The stress relaxation behaviour of liquid crystal-forming ethyl celllulose (EC) solutions in m-cresol was determined by means of a cone-plate type viscometer at 30°C. The effect of molecular weight (MW) on the behaviour was also determined. The relaxation behaviour could be fitted with the following equation: where σ_i and σ_f are steady-state shear stresses at shear rate $\dot \gamma _{\rm i}$ and $\dot \gamma _{\rm f}$, σ(t) is time- dependent stress, A₁ and A₂ are constants, τ₁ and τ₂ are relaxation times, t is time, and t_c is a characteristic time. When log σ* was plotted against time, one straight line was obtained for isotropic solutions, whereas anisotropic solutions yielded two straight lines. This suggests that the liquid crystalline solutions have two separate relaxation processes: Process 1 has a relatively short relaxation time, and process 2 has a long one. The parameters τ₁, τ₂, and A₂ were greatly dependent on polymer concentration, combination of $\dot \gamma _{\rm i}$ and $\dot \gamma _{\rm f}$, and MW, whereas A₁ was independent thereof and was close to unity. The process 1 was supposed to be valid for individual molecules, and process 2 for liquid crystalline domains or randomly aggregated or entangled molecules.     

Permeability of oxygen and nitrogen gases in ethyl cellulose solid films retaining cholesteric liquid crystalline order

Ethyl cellulose (EC) films that retain lyotropic and thermotropic cholesteric liquid crystalline order, and an amorphous EC film were prepared. The liquid crystalline order was identified by optical measurements. The comparative permeability of oxygen and nitrogen gases for three kinds of EC film was determined, and the applicability of the EC films that retained cholesteric liquid crystalline order to oxygen enrichment are discussed. The permeability of oxygen or nitrogen gas for the liquid crystalline films was lower than that for the amorphous ones. The activation energy for the permeability coefficient of oxygen gas was ca. 3.5 kcal/mol. The ratio of permeability coefficient for oxygen gas to that for nitrogen gas was less than 4. Interestingly, the permselectivity of oxygen and nitrogen gases for the liquid crystalline films was greater than that for the amorphous ones. © 1996 John Wiley & Sons, Inc.     

Self-adjustment of Young's modulus in biomedical titanium alloys during orthopaedic operation

In spinal fixation devices, the Young's modulus of the metallic implant rod should be not only sufficiently low to prevent stress shielding for the patient but also sufficiently high to suppress springback for the surgeon. This paper proposes a novel function of biomedical titanium alloys—self-adjustment of Young's modulus. Deformation-induced ω phase transformation was introduced into β-type titanium alloys so that the Young's modulus of only the deformed part would increase during operation, while that of the non-deformed part would remain low. The Young's modulus increase by deformation was investigated for a binary Ti-12Cr alloy. This alloy successfully underwent deformation-induced ω phase transformation and exhibited the increase in the Young's modulus by deformation.     

Swelling behavior of crosslinked hydroxypropylcellulose films retaining cholesteric liquid crystalline order,II. Effects of temperature,solvent, and pH

Crosslinked hydroxypropylcellulose (HPC) films were cast from the cholesteric liquid crystalline HPC solution in methanol. The films retained the cholesteric liquid crystalline order. The dependences of swelling behavior of our films in water and propanol on temperature and on pH of the solvent were determined. The response of our films to the changes in water, temperature and in pH was discussed. In water, the equilibrium swelling ratio (B_e) decreased with temperature whereas B_e increased with temperature in propanol. For a given composition of water and propanol, B_e was independent of temperature. B_e in the acidic solvents was higher than in the alkaline solvents. The response data to the stepwise change in temperature revealed that the deswelling behavior was more rapid than the swelling behavior in water, and the swelling-deswelling behavior was reversible. The response to the stepwise change in pH was almost the same as that of the change in temperature, but the surface of the film was attacked by the acid and became fluffy with increasing soaking time.