Rotary friction,dipole moments,conformation and rigidity of polybutylisocyanate molecules in solution

Experimental data on the dependence of the rotatory diffusion coefficients and dipole moments on molecular weight and the theory of hydrodynamic properties and of the size of wormlike chains were used for determining the main conformational characteristics of the polyisocyanate chain S is the number of molecular units in a segment, λ is the length of the projection of the monomer unit on the axis of the molecule, and μ_o is the dipole moment of the monomer unit. The values of S and λ agree with those found previously by hydrodynamic methods. It was shown that the flat cis-structure of the polyisocyanate chain corresponds to values of λ = 2 × 10^?8cm andμ_o = 1·8D. Analysis of experimental data indicates that dimensions of “geometrical” and “electrical” segments in the PBIC chain are identical.     

Chain dimensions and transport coefficients of sodium poly(isoprenesulfonate) in aqueous sodium chloride

Sodium poly(isoprenesulfonate) (NaPIS) fractions consisting of 1,4‐ and 3,4‐isomeric units (0.44:0.56) and ranging in molecular weight from 4.9 × 10³ to 2.0 × 10⁵ were studied by static and dynamic light scattering, sedimentation equilibrium, and viscometry in aqueous NaCl of a salt concentration (C_s) of 0.5‐M at 25 °C. Viscosity data were also obtained at C_s = 0.05, 0.1, and 1 M. The measured z‐average radii of gyration 〈S²〉_z^1/2, intrinsic viscosities [η], and translational diffusion coefficients D at C_s = 0.5‐M showed that high molecular weight NaPIS in the aqueous salt behaves like a flexible chain in the good solvent limit. On the assumption that the distribution of 1,4‐ and 3,4‐isomeric units in the NaPIS chain is completely random, the [η] data for high molecular weights at C_s = 0.5 and 1 M were analyzed first in the conventional two‐parameter scheme to estimate the unperturbed dimension at infinite molecular weight and the mean binary cluster integral. By further invoking a coarse‐graining of the NaPIS molecule, all the [η] and D data in the entire molecular weight range were then analyzed on the basis of the current theories for the unperturbed wormlike chain combined with the quasi‐two‐parameter theory. It is shown that the experimental 〈S²〉_z, [η], and D are explained by the theories with a degree of accuracy similar to that known for uncharged linear flexible homopolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2071–2080, 2001     

LIGHT SCATTERING OF POLYSACCHARIDE FROM LACQUER IN AQUEOUS SOLUTION

The polysaccharide having weight-average molecular weight M_w=1. 09×10~5, isolated from the sap of lac trees (Vietnam), was separated into 12 fractions by aqueous-phase preparative gel permeation chromatography. The molecular weights and molecular weight distributions of the fractions were measured in aqueous 0.08M KCl/0.01 M NaAc and 0.4M KCl/0.05M NaAc at pH =7. 6 by light scattering, viscometry and gel permeation chromatography. The Mark-Houwink equation in aqueous 0.08M KCl/0.01M NaAc at 30℃was found to be [η]= 2.28×10~(-2) M_w~(0.52) (cm~3/g), which indicated the polysaccharide chain in the aqueous solution to be a spherical random coil.     

Electrostatic long-range and short-range interactions in linear poly(allylamine hydrochloride) chains

The efficiencies of two azo initiators in the polymerization of allylamine salts in water and organic solvents were compared. The hydrodynamic and molecular characteristics of poly(allylamine hydrochloride) in 0.1 M NaCl in the molecular mass range M×10^?3=18?65 were studied, and the scaling relationships were derived for the intrinsic viscosity ([η]=7.65×10^?3 M ^0.8±0.1), translational diffusion coefficient (D ₀=2.41×10^?4 M ^{?(0.59±0.05)}), and velocity sedimentation coefficient (s ₀=2.77×10^?15 M ^0.41±0.05). The hydrodynamic data were interpreted in terms of electrostatic long-range and short-range interactions. The equilibrium rigidity of poly(allylamine hydrochloride) chains in 0.1 M NaCl and its structural and electrostatic constituents were quantitatively estimated. It was shown that the conformation of poly(allylamine hydrochloride) chains in pure water is close to rodlike.     

Hydrodynamic and conformational properties of silicon-substituted addition-type polynorbornene macromolecules

Seven polynorbornene samples containing trimethylsilyl side groups that were prepared by the addition polymerization of 5-trimethylsilyl-2-norbornene in the presence of catalytic systems (π-C₅H₉NiCl)₂-methylaluminoxane and nickel naphthenate-methylaluminoxane have been studied by translational isothermal diffusion and viscometry. The molecular masses of the polymer samples are measured. Kuhn-Mark-Houwink equations for diffusion coefficient D and intrinsic viscosity [η] are determined in toluene at 25°C: D = 6.94 × 10^?4 M ^?0.61 and [η] = 1.53 × 10^?3 M ^0.82. The equilibrium rigidity of polymers chains is estimated as A = 47 ± 9 Å. The conformational features of the silicon-containing polynorbornene are analyzed by the PM3 quantumchemical semiempirical method on the basis of simulation of its decamer chain fragments. In terms of microstructure and equilibrium rigidity, the above-described addition poly(trimethylsilylnorbornene) is close to poly(trimethylsilylpropyne) synthesized using niobium pentachloride as a catalyst. This finding explains similar membrane gas-separation properties of these polymers.     

Studies of the hydrated oxonium radical H3O·(H2O)n and the ammoniated ammonium radical NH4·(NH3)n by neutralized ion beam techniques

Neutralized ion beam studies of the clusters NH₄·(NH₃)_n and H₃O·(H₂O)_n,n = 0–3, and their fully deuterated analogs are presented. Stabilization of the hypervalent monomer radicals is found to accompany solvation. Cluster stability is found to decrease with increasing size. Reasons for this observation are discussed. Internally excited clusters are found to stabilize efficiently through the sequential loss of structural units (NH₃ or H₂O). The mixed isotopic dimer clusters (D₂¹⁸O)·D·(D₂¹⁶O) and (HDO)·D·(D₂O) are also investigated. Presence of the D₃¹⁶O radical structural unit is found to be crucial to dimer stability. This is consistent with the results of earlier investigations involving the monomer which showed the surprising lifetime progression τ(D₃¹⁶O) ≫; τ(D₃¹⁸O) ⩾ τ(H₃¹⁶O).     

Lanthanoid‐Peroxo‐Komplexe mit μ3‐η2:η2:η2‐(O22—)‐Koordination. Die Kristallstrukturen von [Ln4(O2)2Cl8(Py)10] · Py mit Ln = Sm,Eu, Gd

Lanthanoid Peroxo Complexes with μ₃‐η²:η²:η²‐(O₂^2—) Coordination. Crystal Structures of [Ln₄(O₂)₂Cl₈(Py)₁₀] · Py mit Ln = Sm, Eu, Gd The four‐nuclear peroxo complexes [Ln₄(O₂)₂Cl₈(Py)₁₀]·py (py = pyridine) with Ln = Sm ( 1 ·py), Eu ( 2 ·py) und Gd ( 3 ·py) are formed as pale yellow ( 1 ·py) and colourless ( 2 ·py and 3 ·py) crystals by action of atmospheric oxygen on heated solutions of the anhydrous trichlorides LnCl₃ in pyridine/ diacetone alcohol (4‐hydroxy‐4‐methyl‐2‐pentanone). According to the X‐ray structural analyses the three complexes crystallize isostructural in the triclinic space group PP1¯ with two formula units per unit cell. 1—3 form centrosymmetrical molecular structures, in which the four lanthanoid atoms in coplanar array are linked via the two peroxo groups in a hitherto unobserved μ₃‐η²:η²:η² coordination. Additionally, they are bonded by four �μchloro bridges. Two of the Ln atoms complete their coordination sphere by three pyridine molecules each, the other two by two chlorine atoms and two pyridine molecules. The gadolinium compound is additionally characterized by its complete vibrational spectrum (i.r. and Raman).     

Polymerization of vinyl chloride with organolithium compounds. V. Fractionation and solution properties of high molecular weight poly(vinyl chloride)

A sample of high molecular weight poly(vinyl chloride) (PVC) was fractionated by classical precipitation fractionation and gel-permeation chromatography (GPC) on a preparative scale. The fractions thus obtained were characterized by light scattering, viscometry, and by the GPC method. The measured weight-average molecular weights M?_w, intrinsic viscosity [η], and polydispersity index M?_w/M?_n values were used for the determination of the Mark-Houwink equation, [η] = KM^a, for PVC in cyclohexanone (CHX) at 25°C valid for molecular weights from 100,000 to 625,000.     

Study on Dynamic Interfacial Tension of 3‐Dodecyloxy‐2‐hydroxypropyl Trimethyl Ammonium Chloride at n‐Decane/Water Interface

Dynamic interfacial tension (DIT) and interface adsorption kinetics at the n‐decane/water interface of 3‐dodecyloxy‐2‐hydroxypropyl trimethyl ammonium chloride (R₁₂TAC) were measured using spinning drop method. The effects of R_nTAC concentration and temperature on DIT have been investigated, the reason of the change of DIT with time has been discussed. The effective diffusion coefficient, D _a, and the adsorption barrier, ?_a, have been obtained with extended Word‐Tordai equation. The results show that the higher the concentration of surfactants is, and the smaller will be the DIT and the lower will be the curve of the DIT, and the R₁₂TAC solutions follow a mixed diffusion‐activation adsorption mechanism in this investigation. With increase of concentration in bulk solution of R₁₂TAC from 8×10^?4 mol · dm^?3 to 4×10^?3 mol · dm^?3, D _a decreases from 2.02×10^?10 m^?2 · s^?1 to 1.4×10^?11 m^?2 · s^?1 and ? _a increases from 2.60 kJ · mol^?1 to 9.32 kJ · mol^?1, while with increase of temperature from 30°C to 50°C, D _a increases from 2.02×10^?10 m^?2 · s^?1 to 5.86×10^?10 m^?2 · s^?1 and ε_a decreases from 2.60 kJ · mol^?1 to 0.73 kJ · mol^?1. This indicates that the diffusion tendency becomes weak with increase strength of the interaction between surfactant molecules and that the thermo‐motion of molecules favors interface adsorption.     

Low angle laser light scattering and photon correlation spectroscopy in surfactant vesicles

Using low angle laser light scattering, weight averaged molecular weights, M?_w, diffusion coefficients, and hydrodynamic radii, R_H, have been determined for completely synthetic surfactant vesicles, prepared by ultrasonic irradiation of dioctadecyldimethylammonium chloride. DODAC, and dihexadecylphosphate. DHP dispersion. Both the M?_w and R_H values were found to decrease exponentially as a function of sonication time. At the limit, M?_w and R_H for DODAC vesicles are 12.6 × 10⁶ dalton and 396 Å, and those for DHP vesicles are 23 × 10⁶ dalton and 595 Å. Calculations indicate both vesicles to be prolates.     

Molecular dimensions of polydipropylsiloxamer

The molecular dimensions of polydipropylsiloxamer were studied by intrinsic viscosity measurements in toluene and in 2-pentanone. The relationships between the molecualr weight and the intrinsic viscosity were found to be: [η]_25°C., toluene = 4.35 × 10^?4 M^0.58; [η]_θ(10°C.), toluene = 1.09 × 10^?3 M^0.5; [η]_θ(76°C.), 2-pentanone = 8.71 × 10^?4 M^0.5. This held reasonably well for molecular weights from 25,000 to 3000,000. The root-mean-square end-to-end length ratio, (r₀² /M)^1/2 as calculated from the constant K, exceeds the free rotation value by approximately 100%. The disparity is greater than that found with polydimethylsiloxamer, indicating a lower degree of flexibility for the polydipropylsiloxamer. This is largely due to the short range steric interaction between near neighboring units of the chain. Gel permeation chromatography was also employed to demonstrate the lower degree of flexibility for polydipropylsiloxamer as compared with polydimethylsiloxamer.     

The structure of μ-oxo dimer of aluminium(III) porphyrin: a theoretical study

The gas-phase molecular structure of μ-oxo dimer of aluminium(III) porphyrin, (AlP)₂O, has been studied for the first time by density functional theory calculations using the B3LYP and M06 functionals and triple-ζ valence basis sets. The molecule has two conformers with equilibrium structures of D _4d and D _4h symmetries with parallel macrocycles and aluminium-oxygen distances of 1.680–1.684 Å (M06/cc-pVTZ). The aluminium atom lies out of the plane of the four central nitrogen atoms and forms a square-based pyramid with them, with the following parameters (M06/cc-pVTZ): r(Al–N) = 2.030–2.031 Å, r(N···N) = 2.803–2.804 Å (the side of the pyramid base), z(Al)–z(N) = 0.434–0.446 Å (the height of the pyramid).     

Rotational diffusion of 9,10-diphenylanthracene in di-n-butyl phthalate solutions of polystyrenes by the fluorescence polarization method: Dependence on polymer concentration and molecular weight

A versatile double-beam polarization fluorimeter has been constructed for measuring the polarization of fluorescence from polymer solutions, melts, and glasses. Polarizations can be determined over a range of temperatures from ?20 to +80°C in a controlled atmosphere with a precision of ±0.001 to ±0.005 for the studies reported herein. Data collected at different temperatures for 1.5 × 10^?5M solutions of 9,10-diphenylanthracene (PA) in di-n-butyl phthalate (BP) fit a relation of the Perrin type, 1/P = (1/P₀) + (ST/_η1), where P is the polarization, T is the absolute temperature, and _η1 is the solvent viscosity. The constants P₀ and S were 0.400 ± 0.005 and (7.4 ± 0.3) × 10^?3 P/°K, respectively. Polarizations were also determined at 25.0 ± 0.1°C for BP solutions containing 1.5 × 10^?5M PA and polystyrenes at various weight fractions w₂ and molecular weights M. Rotational friction coefficients ζ_r deduced from these data showed no dependence on M from 5.1 × 10⁴ to 8.6 × 10⁵ g/mole, and a gradual increase as w₂ was varied from 0 to 0.1. It is concluded from these results that PA is an especially attractive emitter for rotational diffusion studies in nonaqueous systems, and that the abrupt changes in ζ_r with w₂ and M observed for some other emitter–polymer systems and attributed to onset of coil overlap are not universal characteristics of such systems.     

Synthesis of the dimetal compounds [FeW{μ-PPh2 · CH · CH2 C(C6H4Me-4)}(CO)5(η5-C5Me5)] and [FeMo{μ-PPh2 · CH · CH2 · C(C6H4Me-4)}(CO)5(η5-C5H5)]; molecular structure of the iron-tungsten compound

Reactions between diphenyl(vinyl)phosphine and the compounds [FeW(μ-CC₆H₄Me-4)(CO)₅(η⁵-C₅Me₅)] and [FeMo(μ-CC₆H₄Me-4)(CO)₆(η⁵-C₅H₅)] result in a coupling of the vinyl and p-tolylmethylidyne groups at the dimetal centres to produce the PPh₂ · CH · CH₂ · C(C₆H₄Me-4) fragment, which bridges the metal-metal bonds. This was confirmed by an X-ray diffraction study on [FeW{μ-PPh₂ · CH · CH₂ · C(C₆H₄Me-4)}(CO)₅(η⁵-C₅Me₅)].     

Molecular characterization of a hyperbranched polyester. I. Dilute solution properties

A hyperbranched polyester was fractionated by precipitation to produce 10 fractions with molecular weights between 20 × 10³ and 520 × 10³ g mol^?1. Each of these fractions was examined by size exclusion chromatography, dilute‐solution viscometry, intensity, and quasi‐elastic light scattering in chloroform solution at 298 K. High‐resolution solution‐state ¹³C NMR was used to determine the degree of branching; for all fractions this factor was 0.5 ± 0.1. Viscometric contraction factors, g′, decreased with increasing molecular weight, and the relation of this parameter to the configurational contraction factor, g, calculated from a theoretical relation suggested a very strong dependence on the universal viscosity constant, Φ, on the contraction factor. A modified Stockmayer–Fixman plot was used to determine the value of (〈r²〉_o/M_w)^1/2, which was much larger than the value for the analogous linear polymer. The scaling relations of the various characteristic radii (R_g, R_h, R_T, and R_η) with molecular weight all had exponents less than 0.5 that agreed with the theoretical predictions for hyperbranched polymers. The exponent for R_g was interpreted as fractal dimension and had a value of 2.38 ± 0.25, a value that is of the same order as that anticipated by theory for branched polymers in theta conditions and certainly not approaching the value of 3 that would be associated with the spherical morphology and uniform segment density distribution of dendrimers. Second virial coefficients from light scattering are positive, but the variation of the interpenetration function, ψ, with molecular weight and the friction coefficient, k_o, obtained from the concentration dependence of the diffusion coefficient suggests that chloroform is not a particularly good solvent for the hyperbranched polyester and that the molecules are soft and penetrable with little spherical nature. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1339–1351, 2003     

Ethylene propylene diene terpolymers produced with a homogeneous and highly active zirconium catalyst

EPDM terpolymers with ethylidene norbornene as diene monomer could be prepared by means of a soluble Ziegler catalyst formed from biscyclopentadienyl zirconium dimethyl and methylaluminoxane. The overall activities lie between 100 and 1000 kg EPDM/(molZr h bar), obtainable at zirconium concentrations as low as 5 × 10^?7 mol/L. After an induction period (0.5–5 h) the polymerization rates increased and then leveled to a value which was constant for several days. From copolymerization kinetics reactivity ratios r₁₂ = 31.5, r₂₁ = 5 × 10^?3, and r₁₃ = 3.1 could be derived, and by ¹³C-NMR spectroscopy r₁₂ · r₂₁ = 0.3 was found (1: ethylene, 2: propylene and 3: ethylidene norbornene). The regiospecifity of the catalyst toward propylene leads exclusively to the formation of head-to-tail enchainments. The diene polymerizes via vinyl polymerization of the cyclic double bond, and the tendency to branching is low. Molecular weights were estimated between 40,000 and 160,000. The average molecular weight distribution of 1.7 is remarkably narrow. Glass transition temperatures of ?60 to ?50°C could be observed. The cure behavior and the physical properties of cured samples were also tested.     

The formation and crystal and molecular structures of (η5-pentamethylcyclopentadienyl)(η5-cyclopentadienyl)dichloro-titanium, -zirconium and -hafnium

A reaction between (η⁵-C₅Me₅)TiCl₃ and C₅H₅Tl in benzene solution has afforded (η⁵-C₅Me₅)(η⁵-C₅H₅)TiCl₂ (I) in quantitative yield. (η⁵-C₅Me₅)(η⁵-C₅H₅)HfCl₂ (III) has been prepared in 83% yield from a reaction between (η⁵-C₅Me₅)HfCl₃ and C₅H₅Na·DME in refluxing toluene solution. The crystal and molecular structures of (η⁵-C₅Me₅)(η⁵-C₅H₅TiCl₂ (I), (η⁵-C₅Me₅)(η⁵-C₅H₅)ZrCl₂ (II) and (η⁵-C₅Me₅)(η⁵-C₅H₅HfCl₂ (III) have been determined from X-ray data measured by counter methods. The three compounds are isostructural, crystallizing in the orthorhombic space group Pnma. The cell constants are: (I): a 9.873(1), b 12.989(3), c 11.376(4) Å and D_calc 1.45 g cm^?3 for Z = 4; (II): a 9.930(3), b 13.231(9), c 11.628(3) Å and D_calc 1.58 g cm^?3 for Z = 4; (III): a 9.938(1), b 13.156(2), c 11.582(2) Å and D_calc 1.97 g cm^?3 for Z = 4. In each case the metal atom resides on a crystallographic mirror plane which bisects both cyclopentadienyl rings and the ClMCl bond angle. The MCl bond lengths are 2.3518(9) for I, 2.4421(9) for II and 2.415(1) Å for III. The metal—cyclopentadienyl and metal—pentamethylcyclopentadienyl bond distances average 2.38(5) and 2.42(2) Å for I, 2.50(4) and 2.53(2) Å for II, and 2.48(4) and 2.50(1) Å for III respectively.     

Hydrodynamic properties and statistical coil dimensions of poly(o-chlorostyrene)

The theta temperature for the system poly(o-chlorostyrene)-methyl ethyl ketone has been determined as 24·5°. The samples used in the determination were prepared by radical polymerization. The dependence of intrinsic viscosity on molecular weight has been measured in methyl ethyl ketone at 24·5° and found to be $\text{η}{}_{\mathrm{\theta }}\text{= 4·68 × 10}{}^{\mathrm{?4}}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{\mathrm{<mtext>M1</mtext><mtext>2</mtext>}}$. The ratio 〈s₌²〉/M was found, by light scattering, to be 5·60 × 10^?18 cm². Analysis of the solution properties indicates that the Kurata-Yamakawa theory is valid in the vicinity of the Flory temperature (UCST).     

Asymptotic behaviour of molecular bound state wavefunctions

Upper bounds are derived for |r^μ_i|, μ = 1,2, ·, where ? denotes an exact electronic bound state wavefunction of a molecular system in the Born-Oppenheimer approximation, and r_i is the distance of the ith electron from an appropriately chosen point, e.g., the molecular center. It is further shown that ? decays exponentially if r_i → ∞.