Solution properties and chain conformation characteristics of cellulose tricarbanilate

Fractions of two cellulose tricarbanilate samples were characterized by light-scattering (weight-average molecular weight, second virial coefficient, mean-square radius of gyration), gel permeation chromatography (polydispersity index), and viscometry (intrinsic viscosity) in tetrahydrofuran and acetone. The intrinsic viscosity data were analyzed in terms of the theory developed for the continuous wormlike cylinder model, and the chain parameters (Kuhn statistical segment length λ^?1, chain diameter d, and shift factor M_L) were evaluated. The molecular-weight dependence of the mean-square radius of gyration in tetrahydrofuran was calculated for the Kratky—Porod chain model and compared with the experimental results. Data on the intrinsic viscosity and radii of gyration for other solvents at temperatures from 0 to 100°C were analyzed in the same way, and the effects of solvent and temperature on the statistical segment length were evaluated. Polymer—solvent interaction parameters were estimated from the second virial coefficients.     

Polysaccharides of Iris I. Glucomannan fromIris sogdiana

Several fractions of alkali-soluble polysaccharides have been isolated from the seeds ofIris sogdiana Bge. The separation of one of the fractions has yielded a glucomannan consisting of glucose and mannose residues in a ratio of 1:1.2. On the basis of the results of oxidation with chromium trioxide of the acetate of the glucomannan, and of periodate oxidation and methylation, it has been established that its molecule consists of a linear chain composed of β-D-glucopyranose and β-D-mannopyranose residues connected by β-1→4 bonds, although the presence of branching is not excluded. The possibility has been shown of isolating D-mannose by the hydrolysis of the seeds.     

Small-angle x-ray scattering measurements on dilute solutions of polyisobutene by use of kratky cone collimation

SAXS measurements on dilute solutions of polyisobutene in n-hexane (M _ν = 25,600?3.55 × 10⁶, c < 53 g/liter) were carried out by combining conventional slit collimation with the new cone collimation technique. With a fractionated sample (M _ν = 25,600; U < 0.2) the radius of gyration (R = 48 Å), the cross-sectional radius of gyration (R_q = 3.9 Å), the molecular weight per unit length (M/L = 22.8 Å^?1), and the Porod persistence length (a^* = 8.1 Å) are found. The persistence length appears to be dependent on the molecular weight. The partial specific volume ν of polyisobutene in n-hexane also depends on the molecular weight according to ν = 1.025 + 105/M _ν (cm³/g).     

Hydrodynamic invariant of polymer molecules

The theories of hydrodynamic properties of macromolecules in solution leading to an invariant relationship between the values of the intrinsic viscosity, [η], the molecular weight, M, and the translational friction coefficient of the molecule, f, have been considered. The review of experimental data comprising as much as about 2000 fractions of various polymers suggests that for all flexible-chain and moderately rigid-chain molecules the hydrodynamic parameter A₀ = kη₀(M[η]/100)^1/3f^?1 is actually an invariant independent of the chain length and the thermodynamic strength of the solvent and for moderately polydisperse samples also independent of the degree of their polydispersity. For polymers with very rigid chains the parameter A₀ has a high value over the experimentally investigated range of M. These conclusions make it possible to recommend the use of the following average experimental values of the invariant A₀ for the determination of M of polymers from the values of [η] and f: for flexible-chain and synthetic polymers with moderately high chain rigidity (3.2 ± 0.2) · 10^?10, for polymers with high chain rigidity (3.7 ± 0.4) · 10^?10, and for cellulose derivatives and other polysaccharides with molecular dispersity of nonelectrolyte solutions (3.30 ± 0.30) · 10^?10 erg deg^?1 mol^?1/3. The fact that the experimental value of A₀ = 3.2 · 10^?10 does not coincide with the value of A_∞ = 3.8 · 10^?10 erg deg^?1 mol^?1/3 predicted by the theories of translational friction and viscosity of macromolecules implies that the theoretical values of P_∞ = 5.11 and Φ_∞ = 2.8 · 10²³ mol^?1 are mutually incompatible and these theories require further development.     

Structure of cellulose in cuoxam

Cuoxam ([Cu^II(NH₃)₄](OH)₂) is a well known solvent for cellulose. Because of its deep blue colour, it has been used so far only for viscosity measurements. Direct light scattering measurements have not yet been reported in the literature. We carried out static and dynamic light scattering measurements in cuoxam using the blue wavelength of λ₀ = 457.9 nm from an Argon ion laser. The measurements were involved with some difficulties mainly caused by colloidal particles of CuO and Cu(OH)₂ which could be removed by direct centrifugation of the cells. Furthermore, the scattering intensity had to be corrected for extinction. The refractive index increment was taken from the literature. 12 samples of different molecular weight and different origin were measured, and common power law behavior was found in a region up to about DP_w = 1000 for both, the radius of gyration R_g and the hydrodynamic radius R_h, derived from the diffusion coefficient D_z. At higher degrees of polymerization characteristic deviations to lower radii occurred.These deviations are not caused by aggregation since the DP_w's agreed with those from the cellulose tricarbanilates. The quantitative analysis of the radii and the angular dependence of the scattered light allowed determination of the chain stiffness. A Kuhn segment length of I_k = 25.6 (±6.2) nm and a characteristic ratio C_∞ = 49.6 (±12.0) were derived. These values are close to those for cellulose-tri-carbanilate in dioxane.The reason for the increased stiffening is discussed on the basis of a special H-bond model.     

Proposed GPC and intrinsic viscosity analyses of randomly crosslinked polymers having primary distributions of the schulz-zimm form

A mathematical treatment is presented for the gel-permeation chromatographic and intrinsic viscosity behavior of randomly crosslinked polymers having primary molecular weight distributions of the Schulz-Zimm form. Kimura's serial solution of the integro-differential equation derived by Saito for randomly crosslinked polymers is employed for the distribution function. The intrinsic viscosity of a molecule containing i crosslinks is assumed related to that of a linear molecule of the same number of units through [η]_br/ = g_i^½[η]_l where g_i = (R_br²)_i/R_l² = {[1 + (i/6)]^½ + (4i/3π)}^?½. R_brand R_l denoting the root-mean-square radii of gyration of branched and linear chains of the same mass. It is also assumed that GPC elution is controlled by the hydrodynamic volumes of the molecules. Representative calculation results are displayed for polymers with a narrow primary distribution and the “most probable” primary distribution. Results for the latter polymers are compared with those previously obtained by a somewhat different mathematical approach.     

The structure of the glucan of Arum korolkovii

A glucomannan has been isolated from the tubers ofArum korolkovii Regel. It has been shown that the polysaccharide contains O-acetyl groups and consists mainly of (1 → 4)-β-linked aldohexopyranose units of glucose and mannose in a ratio of 1:1.6. The nonreducing ends of the glucomannan are glucose residues, and branching is localized at C₂ and C₃ of mannose.     

Configurational statistics of polysaccharides. VI. Linear (1→4)-linked galactan

The conformational energies for (1→4)-linked α-D- and β-D-galactans have been computed by considering nonbonded, torsional, and electrostatic interactions. The electrostatic interactions are estimated by assigning the charges to various atoms in the molecule by the method of Del Re. The characteristic ratios C_N = 〈r²〉₀/Nl_v² are computed for α-D- and β-D-galactans as a function of the degree of polymerization N and the angle τ at the bridge oxygen atom. These values of characteristic ratios obtained for α-D-galactan are very much higher than for β-D-galactan, indicating that the former assumes a highly extended conformation compared to the latter. The values of characteristic ratios of both these polysaccharides show a decrease with increase in τ similar to that observed for other (1→4)-linked polysaccharides. The calculated values of C_∞ of (1→4)-linked polysaccharides show no correlation with the number of allowed conformations but are affected both by the orientation of the interunit glycosidic bonds and the hindered potential associated with chain units. It has also been shown that the magnitude of the steric factor σ may not be used as an index of flexibility for polysaccharides which differ in type of linkage.     

Light-scattering studies on solutions of cellulose in the ammonia / ammonium thiocyanate solvent system. II. Quasielastic light-scattering and liquid crystal study

This is the second part of a two–part study of the NH₃NH₄SCN cellulose solvent system. Quasielastic light scattering was used to determine the diffusion coefficients of cellulose in solution and the effective hydrodynamic radius of the dissolved molecules. Additionally, the system was studied using light microscopy to determine the minimum critical volume fraction or liquid crystal formation. Very little change was found in the diffusion coefficients with change in cellulose concentration indicating little interaction between the chains in solution. Values of 7.69 and 2.66 × 10⁸ cm²/s were measured for samples having a degree of polymerization of 153 and 969. The value of the coefficient relating the hydrodynamic volume to the radius of gyration was found to be in the range of 0.33 to 0.53, indicating an extended coil conformation according to the Kirkwood-Riseman theory. The minimum critical volume fractions necessary for liquid crystal formation, υ₂′ were 0.039, 0.038, and 0.048 for the three solvent compositions studied. The values calculated for υ₂′ based on the measured persistence lengths were much larger than the predicted values, indicating strong deviation from theory or possible aggregation in the system.     

Light-scattering studies on polystyrenes in isorefractive poly(methyl methacrylate)–toluene “solvents”

The rms radii of gyration 〈S²〉^1/2 and second virial coefficients Γ₂ of five monodisperse polystyrenes (M × 10^?5 = 1.6, 2.8, 4.2, 6.6) were measured in isorefractive toluene–poly(methyl methacrylate) (M?_v = 4.0 × 10⁴, 1.6 × 10⁵, and 6.3 × 10⁵) “solvents.” For a given PMMA, the concentration at which the θ condition (defined by Γ₂ = 0) was reached was independent of PS molecular weight, but varied inversely with PMMA molecular weight (0.10, 0.056, and 0.023 g/mL, respectively). When this θ condition is reached by adding PMMA to toluene, the radii of gyration are decreased by only about 15%, much less than when it is reached by going to a poor, low-molecular-weight solvent. This reflects the exclusion of PMMA from the PS coils, the internal environment of which is essentially pure toluene.     

Light-scattering of polyamide hydrazide solutions and conformational characteristics of its molecules

Light-scattering measurements have been carried out for 18 samples of polyamide hydrazide (PAH) in dimethylsulphoxide (DMS) with an over 10-fold variation in molecular weights. It was shown that the excluded volume effect in DMS does not appreciably affect the size of PAH molecules. The length of the Kuhn segment (A ≈ 240 · 10^?8 cm) was estimated from the experimental determinations of molecular weights $\text{M}{}_{\mathrm{w}}$ and the radii of gyration 〈R²〉_z. Viscometric determination of the rigidity of PAH chains yields the value of A ≈ 200 · 10^?8 cm and the hydrodynamic diameter d ≈ 5 · 10^?8 cm. The whole collection of data shows that PAH is a typical rigid-chain polymer; the extended conformation is due to the backbone rigidity tather than to the excluded volume effects.     

Conformational changes of a polyelectrolyte in mixtures of water and acetone

Samples of a polyelectrolyte poly(methacryloylethyl trimethylammonium methylsulfate), PMETMMS, with molar masses M_w = 22−25 × 10⁶ were examined with viscosity, static light scattering, and conductivity measurements in a water–acetone solvent. Because acetone is a nonsolvent for this polymer the measurements were performed to determine the influence of the solvent composition, the polymer concentration, and the presence of added ions on the conformation of the polyelectrolyte in mixed solvents. The possible influence of a hydrodynamic field on the polymer conformation was also studied. The viscosity of the polymer solutions as a function of polymer concentration, as well as of the solvent composition, was studied using a broad range of shear rates. When the mass fraction of acetone in the solvent, γ, is below 0.5, the solutions show a usual polyelectrolyte behavior. When γ ≥ 0.80, the polymer adopts a compact conformation. This is observed as a decrease of the radius of gyration, R_g, second virial coefficient, A₂, the viscosity, and also as a change in the conductivity of the solution. The change in the polymer conformation may be induced also by dilution. When 0.60 ≤ γ < 0.80, a gradual decrease in the polymer concentration leads to a sudden decrease of the reduced viscosity, which indicates a decrease in the particle size. The values of M_w measured by static light scattering were constant in all experiments. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1107–1114, 1998     

Conformational behaviour of poly(2,6-dimethyl-1,4-phenylene oxide) in solution—II. Sedimentation coefficients and permeabilities in the semi-dilute region as a function of temperature

Sedimentation and flotation coefficients of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) solutions have been measured as a function of temperature between 60 and 25°. The solvents were toluene and trichloroethane (TCE). Solvent permeabilities have been calculated from the sedimentation or flotation coefficients. PPO is less permeable to the solvents used than polystyrene of comparable molecular weight is to toluene and cyclohexane. Strong solvation of toluene and TCE by PPO molecules is proposed as an explanation for this finding. The measured permeabilities were used to check an earlier calculation of the change of radius of gyration with temperature from intrinsic viscosity data. A larger decrease in radius of gyration with increasing temperature has been calculated in this way than with the earlier assumption of essentially impermeable polymer coils, i.e. with the assumption of the value 2.5 × 10²³ for the universal viscosity parameter Φ₀.     

The nonlinear change in conformation of polyelectrolyte macromolecules in saltless water-organic solvent

High molecular weight polyelectrolyte: poly(dimethylaminoethyl methacrylate) [PDMAEMA] with molecular weights M_W = 28.0×10⁶, 20.0×10⁶, 15.0×10⁶ was investigated in dilute solution by light scattering, flow birefringence and viscometry (at different rate gradients) in a water-acetone system by varying the weight fraction of acetone r in the mixture. At r=0.76 the polymer undergoes a reversible coil-globule transition accompanied by a drastic decrease in intrinsic viscosity [n], mean-square radius of gyration R²_z^1/2 and second virial coefficient A₂, with no change in molecular weight. The coil asymmetry parameter p (p=2.5 at r=0.50) decreases with increasing r and attains unity (completely symmetrical particle) at the transition point (r=0.76). The anomalous behavior of the viscosity of PDMAEMA-water-acetone solutions, detected near the transition point (r=0.6+0.7), is interpreted by formation of local knots of compactization on the molecular chain under the influence of a hydrodynamic field.     

Excluded-volume effects in dilute polymer solutions. IV. Polyisobutylene

Statistical radii of gyration, second virial coefficients, and intrinsic viscosities of sharp fractions (M?_w/M?_n ≈ 1.1) of polyisobutylene (PIB) covering a wide range of molecular weight (1.6 × 10⁵ to 4.7 × 10⁶) were determined in isoamyl isovalerate (IAIV) at a number of temperatures ranging from 20 to 60°C, in n-heptane at 25°C, and in cyclohexane at 25°C by light-scattering and viscosity measurements. It was found that IAIV at 22.1°C is a theta solvent for PIB. Analysis of the data by the methods described in preceding papers of this series indicated that, except for minor differences, the conclusions derived from similar studies with polychloroprene, polystyrene, and poly-p-methylstyrene hold equally for solutions of the typical linear polymer investigated here. In particular, no decisive evidence for the drainage effect was found.     

Differentiation of stereochemistry of glycosidic bond configuration: Tandem mass spectrometry of diastereomeric cobalt-glucosyl-glucose disaccharide complexes

Configurations of glycosidic linkages (α or β) in a series of 1,3-, 1,4-, and 1,6-glucosyl-glucose disaccharides were differentiated by tandem mass spectrometry. Diastereomeric octahedral complexes, [Co⁺³ (acac)₂/disaccharide]⁺, were generated in situ via fast-atom bombardment ionization. Mass-analyzed, ion kinetic energy spectra of the metastable complexes obtained in the absence of collision gas indicated that the major product ion results from the loss of an acetylacetonate ligand, which thus generates the ion [Co⁺²(acac)/disaccharide]⁺. Kinetic energy release measurements for this dissociation display a consistently greater value for complexes that possess an α-linked disaccharide relative to those that possess β-linked disaccharides, regardless of linkage position.     

Characterization of the chain stiffness for a mesogen-jacketed liquid crystal polymer: Poly{2,5-BIS [(4-Methoxybenzoyl)Oxy] Styrene}

Narrow-distribution fractions of poly{2,5-bis[(4-methoxybenzoyl)oxy] styrene} ranging in weight-average molecular weight Mw from 1.1 × 10⁵ to 1.96 × 10⁶ were studied by static light scattering and viscometry in THF at 25 ^° C. From Mw and the intrinsic viscosity [ η ] Mark-Houwink-Sakurada equation was formulated with K=7.54×10⁻⁴ and ≈=0.82. The relation between [ η ] and Mw was analyzed according to Bohdanecky for the Kratky-Porod wormlike chain, the ranges of the mass per unit length M_L and the persistence length q were estimated as 35 nm⁻¹ M<_L42 nm<₋₁ and 11.5 nm <13.5 nm, respectively. The values of ≈ and q indicate that the polymer, though a liquid crystal polymer of the side-chain type, has wormlike chain in dilute solution as most main chain liquid crystal polymers.     

Dielectric relaxation analysis of starch oligomers and polymers with respect to their chain length

Starch belongs to the polyglucan group. This type of polysaccharide shows a broad β-relaxation process in dielectric spectra at low temperatures, which has its molecular origin in orientational motions of sugar rings via glucosidic linkages. This chain dynamic was investigated for α(1,4)-linked starch oligomers with well-defined chain lengths of 2, 3, 4, 6, and 7 anhydroglucose units (AGUs) and for α(1,4)-polyglucans with average degrees of polymerization of 5, 10, 56, 70, and so forth (up to 3000; calculated from the mean molecular weight). The activation energy (E_a) of the segmental chain motion was lowest for dimeric maltose (E_a = 49.4 ± 1.3 kJ/mol), and this was followed by passage through a maximum at a degree of polymerization of 6 (E_a = 60.8 ± 1.8 kJ/mol). Subsequently, E_a leveled off at a value of about 52 ± 1.5 kJ/mol for chains containing more than 100 repeating units. The results were compared with the values of cellulose-like oligomers and polymers bearing a β(1,4)-linkage. Interestingly, the shape of the E_a dependency on the chain length of the molecules was qualitatively the same for both systems, whereas quantitatively the starch-like substances generally showed higher E_a values. Additionally, and for comparison, three cyclodextrins were measured by dielectric relaxation spectroscopy. The ringlike molecules, with 6, 7, and 8 α(1,4)-linked AGUs, showed moderately different types of dielectric spectra. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 188–197, 2004     

The flexibility of rodlike micelles in aqueous solutions and the crossover concentrations among dilute,semidilute, and concentrated regimes

A flexibility parameter, the persistence length, has been evaluated from the radii of gyration and the contour lengths for rodlike micelles of heptaoxyethylene alkyl ethers (C _n E₇,n=12, 14, 16) and tetradecyldimethylammonium chloride (C₁₄DAC) and bromide (C₁₄DAB) at the observed crossover concentrations between dilute and semidilute regimes. The persistence length range is 43–73 nm, except for C₁₂E₇, for which it is 32 nm. The crossover concentrations between dilute and semidilute regimes for the semiflexible rodlike micelles calculated according to Ying and Chu as a function of the molecular weight, the contour length, and the persistence length are consistent with the observed values. The crossover concentration between semidilute and concentrated regimes was, on the other hand, calculated by using the same micelle parameters, including the value of thickness of cross-section of the rodlike micelles. The obtained values are at variance with the observed values. This means that rodlike micelles in semidilute and concentrated solutions might differ in size and/or flexibility from those in dilute solution.     

Water‐soluble acrylamide copolymers. VI. Preparation and characterization of poly[N,N‐dimethylacrylamide‐co‐acrylamide] and control polyacrylamides

This article describes the first of a new series of preparations of water‐soluble acrylamide, substituted acrylamide copolymers and related homopolymers. Objectives of this work were to measure the progressive influence on the hydrodynamic volume and other properties contributed by incorporation of N,N‐dimethylacrylamide (DMA) into a series of high molecular weight acrylamide copolymers. Traditional photoacoustic Fourier transform infrared, ¹³C NMR, and elemental analysis were used for primary characterization. A series of tests using viscometric, gel permeation, chromatographic, and multiangle laser light scattering methods were then used to measure the hydrodynamic volumes of the products. Copolymers incorporating 14, 23, 43, and 63 mol percent DMA with molecular weights of greater than 5 × 10⁶ g/mol were obtained with yields of better than 70%. Aqueous solutions of these polymers showed little or no decrease in radii of gyration or intrinsic viscosity when low concentrations of sodium chloride were added, in contrast to its effect on solutions of polyacrylamide itself. For the copolymers, higher values were obtained for < r_g > and [η], than were observed for acrylamide homopolymers of comparable molecular weight. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3128–3145, 2000