Anionic polymerization of isoprene by the complexes oligoisoprenyllithium/tertiary polyamines in cyclohexane: 3. Structural study of the polymers by 1H n.m.r. at 100 MHz

The microstructure of polyisoprene prepared anionically in the presence of catalytic amounts of N,N,N′,N′-tetramethylethylenediamine (TMEDA) and pentamethyldiethylenetriamine (PMDT) has been studied as a function of $\text{r =}\text{[}\text{TMEDA}\text{]}\text{[}\text{living ends}\text{]}$ and $\text{r =}\text{[}\text{PMDT}\text{]}\text{[}\text{living ends}\text{]}$. No significant effect is observed for r ? 0.5. The structure varies drastically for r > 0.5. The 4,3 addition increases mainly at the expense of the cis4,1 addition and a plateau is reached for r ? 1.0. The results are discussed on the basis of the nature of the living species.     

A simple additivity relation for analysis of heterogeneous catalytic reactors with first order reaction

An isothermal heterogeneous reactor with first order kinetics is characterized by two virtual maximum efficiencies, $\text{N}$_kin and $\text{N}$_tr, which are readily determined from the appropriate kinetic and transport parameters. The actual efficiency of the reactor, which is related to the conversion, X, by X = 1?e^?$\text{N}$, can be accurately approximated as $\text{N}$^?1 = $\text{N}$^?1_tr + $\text{N}$^?1_kin. The overall additivity relation offers a simple approach either to predict the conversion or to extract the kinetic or transport parameters when the reactor behavior is affected by both reaction and diffusion.     

Semiconducting properties of anodic WO3 amorphous films

The semiconducting properties of amorphous WO₃ anodic films grown in different solutions and at different current densities have been investigated. The Mott—Schottky plots have shown that the donor density, N_d, of the grown films is strongly dependent on the films thickness and is not influenced by the nature of the anodizing solutions. The possible influence of the kinetics of anodization on N_d is discussed. The intersection voltages at 1/C²_sc = 0 in the Mott—Schottky plots show a complex dependence on the film thickness. The possibility of obtaining the flat band potential from these plots is also discussed.A linear relationship between the square of the photocurrent and the electrode potential has been observed as previously reported for single crystals. The dissolution rate of anodic WO₃ films is increased under illumination and strongly decreased in presence of Fe^{$\text{2+}\text{3+}$} couple. The kinetics of electron transfer between the amorphous WO₃ anodic films and the Fe^{$\text{2+}\text{3+}$} redox couple in the electrolyte seems to occur in accordance with the theory developed for single crystal semiconductors.     

The θ-behaviour of heterogeneous macromolecules

A polymer chain consisting of N_r segments with a repulsive interaction (binary cluster integral β_r) and N_a ? N_r segments with a stronger, attractive and pairwise saturable interaction (β_a), which is at the averaged θ-point N²_rβ_r + N²_aβ_a = 0 deviations from the predictions of the two parameter theory: $\text{α}{}^2{}_{\mathrm{<mtext>R</mtext>}}\text{? 1 ～ δz}{}_{\mathrm{<mtext>r</mtext>}}\text{< 0}$ and A₂ ～ δz_r > 0 with $\text{δz}{}_{\mathrm{<mtext>r</mtext>}}\text{～ β}{}_{\mathrm{<mtext>r</mtext>}}\text{(}\text{N}{}_{\mathrm{<mtext>a</mtext>}}\text{N}{}_{\mathrm{<mtext>r</mtext>}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. It is shown that the deviations from the universal behaviour are due to the existence of an intermediate length scale $\text{～}\text{N}{}_{\mathrm{<mtext>a</mtext>}}\text{N}{}_{\mathrm{<mtext>r</mtext>}}$.     

Effect of temperature and frequency in fatigue of polymers

The effects of frequency and temperature on fatigue crack propagation rate in poly(methyl methacrylate) and polycarbonate have been studied using centrally notched plate specimens cycled in tension between constant stress intensity limits. Crack growth was monitored at frequencies between 0.1 Hz and 100 Hz and at temperatures between ?60°C and 40°C. A linear relationship between the cyclic crack growth rate $\text{d}\text{(2a)}\text{d}\text{N}$ and appropriate levels of toughness, K, has been proposed: $\text{d}\text{(2a)}\text{d}\text{N}\text{= A?}{}^{\mathrm{\alpha }}$, where $\text{? =}\text{(λ ? λ}{}_{\mathrm{<mtext>th</mtext>}}\text{)}\text{(K}{}^2{}_{\mathrm{<mtext>1</mtext><mtext>C</mtext>}}\text{? K}{}^2{}_{\mathrm{<mtext>max</mtext>}}\text{)}$, λ = K²_max ? K²_min, λ_th is the threshold limit and A and α are constants. Also, the influence of mean stress intensity was briefly discussed.     

Fluorescence probe for microenvironments: effect of solvent vapour on the properties of vapour-swollen polymers

The effect of solvent vapour on the properties of vapour-swollen vinyl chloride-vinyl acetate ($\text{83}\text{17}$) copolymer has been studied by a fluorescence probe, a p-N,N-dialkylaminobenzylidenemalononitrile derivative (1). Results show that the fluorescence quantum yield ($\text{Ф}{}_{\mathrm{<mtext>f</mtext>}}$) of 1 in vinyl chloride-vinyl acetate ($\text{83}\text{17}$) matrix decreases by a factor of ≈ 10, an indication of the increase in free volume or in polymer chain mobility, upon vapour swelling. The variations of $\text{Ф}{}_{\mathrm{<mtext>f</mtext>}}$ observed in various swollen matrices, which correlate only with the density of the swelling solvent, indicate that there is a profound vapour effect on the properties of swollen polymer. A density effect on the mobility of polymer chains in swollen polymer is proposed.     

Carbon dioxide absorption by turbulent plunging jets of water

The absorption process as taking place in a plunging jet system is investigated. Starting from the assumption that the site of the main mass transfer process is the submerged biphasic jet, a physical model is developed and a mass transfer equation is established.In the second section of the paper, a criterial correlation eqn (35):Sh* = 8.8 (Re. We. Sc. $\text{H}\text{d}{}_{\mathrm{N}}$)^{$\text{1}\text{2}$} for the liquid phase mass transfer coefficients in the system carbon dioxide-water is obtained, on basis of experiments in which the nozzle diameter, jet velocity, jet length through the gas phase and working temperature were varied.This equation correlates in a satisfactory manner the experimental data (the average of the absolute deviation is 14.1%).     

Radical copolymerization of N-(1,1-dimethyl-3-oxobutyl)-acrylamide in different solvents

The influence of different solvents on the copolymerization behaviour of N-(1,1-dimethyl-3-oxobutyl)-acrylamide (diacetone acrylamide, DAAM) with styrene and methyl methacrylate has been investigated. The calculated relative reactivities of DAAM towards the polystyryl and poly(methyl methacrylyl) radicals ($\text{1}\text{r}{}_2$) are practically unaffected by the reaction medium; on the contrary, the relative reactivities of both styrene and methyl methacrylate monomers towards the poly(diacetone acrylamide) radical ($\text{1}\text{r}{}_1$) are influenced by the reaction solvents. This effect, however, is less significant than that found previously for N-methyl acrylamide copolymerization.     

Synthesis of electroreactive polymers from poly (m,p-chloromethylstyrene) and copoly (m,p-chloromethylstyrene-styrene)

Polymerization, and copolymerization with styrene, of m,p-chloromethylstyrene have been carried out at 75°C, in chlorobenzene and in the presence of AIBN ($\text{[}\text{AIBN}\text{] ? 6 × 10}{}^{\mathrm{?2}}$, and $\text{12 × 10}{}^{\mathrm{?2}}\text{m}$, respectively). The polymer molecular weights, determined by g.p.c., are: $\text{M}\text{?}{}_{\mathrm{w}}\text{= 8670}$, $\text{M}\text{?}{}_{\mathrm{n}}\text{= 5860}$, and $\text{M}\text{?}{}_{\mathrm{w}}\text{/-M}{}_{\mathrm{n}}\text{= 1.48}$ for the homopolymer, poly(m,p-chloromethylstyrene), (1a); and $\text{M}\text{?}{}_{\mathrm{w}}\text{= 8805}$, $\text{M}\text{?}{}_{\mathrm{n}}\text{= 5144}$, and $\text{M}\text{?}{}_{\mathrm{w}}\text{/-M}{}_{\mathrm{n}}\text{= 1.71}$ for the copolymer, copoly(m,p-chloromethylstyrene-styrene), (2a). A series of phosphine derivatives of both 1a and 2a are prepared by the reaction of the polymers with either chlorodiphenylphosphine/lithium, or diphenylphosphine/potassium tert. butoxide. A number of other potentially electroreactive derivatives of 2a are obtained by reacting the polymer with 2-aminoanthraquinone, 3-N-methylamino-propionitrile, or 2-(2-aminoethyl) pyridine. The phosphinated polymers are reacted with bis-benzonitrilepalladium-(II) chloride to obtain a series of polymer-palladium(II) complexes containing 8.5–12.9% palladium. Similarly, reaction of the last-named bidentate polymeric ligand with cupric acetylacetonate, or cupric sulphate pentahydrate, produces polymer-copper(II) complexes having 5.8, or 3.3% copper, respectively. The inter/intra-chain nature of some of the side reactions during the derivatization of the chloromethylated polymers, and that of the complex formation between transition metal centres and macromolecular ligands, are briefly discussed in view of the experimental results.     

Optically active poly[thio-1-(N,N-diethylaminomethyl) ethylene]

Poly[thio-1-(N,N-diethylaminomethyl) ethylene] [poly(TDAE)] of different optical purities were prepared by stereoelective polymerization of racemic N,N-diethyl-N-(thiirane-2-ylmethyl) amine (TDAE) using a (1:1) $\text{ZnEt}{}_2\text{R}$ (?) 3,3-dimethyl 1,2-butanediol (R(?)DMBD) chiral initiator system. Optically enriched TDAE samples were isolated as residual monomers. These monomers were thermally polymerized to give optically active poly(TDAE) with randomly distributed R and S repeat units in various proportions. The configuration of the enantiomer preferentially incorporated into growing chains during the stereoelective polymerization was determined as R on the basis of the presence of a positive Cotton effect at 260 nm in the c.d. spectrum of residual monomers. This configuration agrees well with the known homosteric character of the $\text{ZnEt}{}_2\text{(?)}\text{DMBD}$ initiator system. ¹³C n.m.r. spectra of the different optically active poly(TDAE) samples and those of more or less stereoregular racemic ones were compared. It was found that the carbon atom of the main chain methine group is the only one which is stereosensitive. Observed triad effects were used to determine the degree of isotacticity of optically active poly(TDAE)s prepared by thermal polymerization of partly enriched monomers. The stereoelectivity of the initiator system and the optical activity of optically pure TDAE and poly(TDAE) were deduced. Side-chain nitrogen atoms did not show any competitive effect with sulphur atoms in the coordination process to the chiral initiator system.     

The structure of poly(trimethylene terephthalate)

The determination of the crystalline structure of oriented fibres of poly(trimethylene terephthalate) is described. The unit cell is triclinic with the following parameters: $\text{a = 4.6}\text{A}\text{?}$, $\text{b = 6.2}\text{A}\text{?}$, $\text{c = 18.3}\text{A}\text{?}$, α = 98°, β = 90°, γ = 112°. Each cell contains two monomers of one polymer chain. Both methylene bonds are in the gauche conformation. The chain conformation and the packing of chains within the unit cell are discussed in detail and compared with other chemically similar materials, both monomeric and polymeric.     

Reduction electrochimique de la phenothiazine et du fluorobenzene a basse temperature

A well characterized polarographic wave is observed at low temperature (?30°C) for phenothiazine $\text{1}$ (E_{$\text{1}\text{2}$} = ?2.85 V) and fluorobenzene (E_{$\text{1}\text{2}$} = ?2.97 V) in dimethylformamide. The electrochemical reduction of $\text{1}$ leads probably to an NN dimer with consumption of 0.5 F.     

Small-angle neutron scattering by semicrystalline polyethylene

The angular dependence of the intensity of neutron scattering by deuterated polyethylene chains (PED) dispersed in the protonated host (PEH) in the semicrystalline state has been computed over the scattering range $\text{0 < μ < 0.2}\text{A}\text{?}{}^{\mathrm{?1}}$, where μ = (4π/λ)sin(θ/2), for various morphologies that differ according to the mode of chain re-entry into the crystalline lamellae. The scattering functions vary strongly with the tendency for adjacent re-entry. The intensity in the range $\text{0.04 < μ < 0.10}\text{A}\text{?}{}^{\mathrm{?1}}$ is 30–40% greater for the regularly folded morphology than for the ‘switchboard’ model. Calculations for the latter approximate the experimental results of Schelten et al. Optimum agreement with their scattering intensities, and the chain dimensions and degree of crystallinity as well, is achieved by a statistical model in which the chain preferentially re-enters the crystalline layer with a probability of about 0.7. Re-entry, when it occurs, is not required to be adjacent to the preceding sequence.     

Raman scattering from mixtures of poly(ethylene oxide) 2000 with poly(ethylene oxide) 200

The longitudinal acoustic mode fundamental (v₁) and third harmonic (v₃) in 2000 MW PEO with both hydroxy- and methody-end-groups have been observed in the Raman spectrum as a function of 200 MW PEO oligomer content. Measurements of small-angle X-ray spacing I_x permit interpretation using a composite rod model. A good fit to the measured quantities v₁I_x and $\text{v}{}_3\text{v}{}_1$ is obtained with crystal length I_c≈9 nm, crystal modulus $\text{E}{}_{\mathrm{<mtext>c</mtext>}}\text{= 9 ×}\text{10}{}^{10}\text{N}\text{m}{}^2$ and amorphous modulus $\text{E}{}_{\mathrm{a}}\text{= 1 ×}\text{10}{}^{10}\text{N}\text{m}{}^2$. The value of Ic implies a crystalline content of ～70% for the pure polymer; the value of Ec is larger than static determinations and similar discrepancies in other materials are discussed.     

Thermal effects in non-adiabatic binary distillation effects of partial condensation of mixed vapors on the rates of heat and mass transfer and prediction of H. T. U.

In order to investigate thermal effects in binary distillation, theoretical approaches were made by use of a laminar boundary layer theory with uniform suction or blowing at the interface to give the following correlations for heat and mass fluxes:Nu_Gx = 0.332 Re_Gx^{$\text{1}\text{2}$}Pr_G^{$\text{1}\text{3}$}g(F(0), Pr_G)Sh_Gx(J_Axs/N_Ax) = 0.332 Re_Gx^{$\text{1}\text{2}$}Sc_G^{$\text{1}\text{3}$}g(F(0), Sc_G). From the energy balance at the vapor—liquid interface the factors which affect interfacial velocities or F(0) were discussed.Measurements of heat and mass fluxes in a vertical flat-plate wetted-wall column for the methanol-water system were made and gave a good agreement with the theory.A new method for the prediction of H_OG in binary distillation under partial condensation was proposed. The calculated H_OG's gave a fairly good agreement with the observed results.     

Excited triplet states in bituminous coal

The intensities of the broad and narrow lines constituting the e.p.r. spectrum of coal depend on the temperature of measurement. The system of paramagnetic centres related to the broad line does not obey the Curie law and consists of free radicals ($\text{S =}\text{1}\text{2}$) and of centres with singlet ground state (S = 0) and lowest-excited triplet state (S = 1). The singlet-triplet excitation energy, J, is comparable with thermal energy, kT, of lattice vibrations. The system of paramagnetic centres related to the narrow line obeys the Curie law ($\text{S =}\text{1}\text{2}$).     

Crack growth under static and fatigue loading in glassy polymers oriented by cold-rolling

Static and fatigue crack growth in PC and fatigue crack growth in PVC have been studied using anisotropic sheets oriented by cold-rolling. Tests were carried out at room temperature for samples with various degrees of rolling reduction. In static loading for PC, a slight rolling reduction considerably improves the resistance to crack propagation in the case where the crack grows perpendicularily to the rolling direction. The measured values of crack opening displacement were compared with the Dugdale model, taking into account the effect of anisotropy. In fatigue loading for both polymers used, a power law relationship between crack growth rate $\text{d}\text{c}\text{d}\text{N}$ and stress intensity factor range ΔK, i.e., $\text{d}\text{c}\text{d}\text{N=A(ΔK)}{}^{\mathrm{m}}$ where A and m are constants, covers most of the data in spite of the differences in degrees of anisotropy. However, the constants A and m are dependent on the degree of rolling reduction. In PVC, the rolling reduction changes the fatigue fracture mode from a discontinuous growth type to continuous one. All the results show that the rolling reduction has an important effect on crack behaviour.     

Syntheses and conformational studies of poly(S-menthyloxycarbonylmethyl l- and d-cysteines)

S-menthyloxycarbonylmethyl l- and d-cysteines were prepared by the reaction of l- or d-cysteine and (?)-menthyl chloroacetate in liquid ammonia and were then polymerized to poly(S-menthyloxycarbonylmethyll- and d-cysteines) by the N-carboxyanhydride (NCA) method. From the results obtained by means of infra-red spectra, X-ray diffractions, optical rotatory dispersions (o.r.d.), and circular dichroisms (c.d.), $\text{poly}\text{(S-}\text{menthyloxycarbonylmethyl-}\text{l}\text{-cysteine}\text{)}$ was found to be a right-handed α-helix in the solid state and in ethyl ether/chloroform and chloroform solutions. Similarly, $\text{poly}\text{(S-}\text{menthyloxycarbonylmethyl-}\text{d}\text{-cysteine}\text{)}$ was a left-handed α-helix. The helix-coil transition of these polymers was observed in the vicinity of 3–4% trifluoroacetic acid (TFA) in chloroform/TFA mixtures.     

Studies on viscosity behaviour of alkali halides in aqueous N,N′ dimethyl urea solution

The viscosity behaviour of ternary systems comprising alkali halides (concentration range 0.125–3 M) in aqueous N,N′ dimethyl urea (0.6 M) solution, over the temperature range 25–40°C has been investigated. It has been found that Moulik's equation (ν/ν_$\text{0}$)² = M + KC² holds good for these systems for the concentrated region. From the relative viscosity data, the “effective” rigid molar volume, V_e and apparent B coefficient have been computed employing the Breslau-Miller procedure at temperatures 25, 30, 35 and 40°C. These data have been used to explain the structuring effect in N,N′ dimethyl urea solution.