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A series of soluble poly(1,4-divinylbenzene) (PDVB) samples was prepared by anionic polymerization of 1,4-divinylbenzene (DVB) in tetrahydrofuran with a varying amount of diisopropylamine. The dilute solution properties of the PDVB samples were examined with conventional methods including viscosimetry, sedimentation equilibrium, and light scattering measurements. The results suggest a considerable amount of long branches in soluble PDVB though not all of the pendant vinyl groups are consumed to form branches. A tree-like model was proposed for the present system. The data were analysed quantitatively according to this model which yielded a consistent pair of values of the z-average mean-square radius of gyration 〈S2〉 and the intrinsic viscosity [η].

Critically branched polyurethanes of varying molecular weight were prepared from poly(oxypropylene)triol and methylenedi-p-phenylene diisocyanate with and without solvent. The static/dynamic light scattering from DMF solutions of these samples was measured. The results were discussed in terms of the classical (Flory-Stockmayer, FS) and percolation theory of gelation; the bulk-polymerized sample obeyed the FS process, whereas the solution-polymerized samples were better described by the percolation process.

Application des simulations de Monte Carlo. Verification pour le polymethylene, polyoxymethylene, polybutadiene et polyisoprene

Cross-linked polystyrenes were prepared from linear polystyrenes of narrow molecular weight distribution by γ-ray irradiation, and their dilute solution properties were studied by light-scattering. The two-parameter theory was used for the analysis of the data; for this purpose the theory was modified with the use of the theory of cascade processes. It is found that the effect of excluded volume becomes smaller with increase of cross-linking and will be negligible in the critically branched state (very near to gel) as seen in the critically branched polycondensates. The depression of the theta temperature and the increase of the unperturbed dimension were discussed at least qualitatively with the aid of the theories of Orofino and Flory, Benoit et al ., and Vrij and Casassa.

A Fortran computer program has been written to perform the bivariate least squares analysis of light scattering data introduced by Miller and Stepto. The program also carries out the necessary extension to the computer plotting of the results. In the conventional Zimm plot analysis, terms of order c2 (where c = concentration) and x 2 [where x = sin 2 ( ϑ 2) ] , are effectively ignored without theoretical justification, although (i) the intramolecular scattering function P(ϑ) is not generally a linear function of x. and (ii) the effect of the third (and higher) virial coefficients cannot always be neglected. Results for the theta system polystyrene cyclohexane, and also for the systems poly x-methyl styrene in benzene and trans-decalin using published data indicate that the inclusion of these terms provides further insight into the dilute solution properties of macromolecules.

Imogolite, though achiral, forms cholesteric spherulites in the anisotropic phase as shown by the regular striations arranged in a swirl-like or fingerprint pattern observed through a polarizing microscope. Electron microscopy revealed the raft-like imogolite sheet floating in the anisotropic phase. The structure of the imogolite sheet was deduced from periodicities observed by an electron microscope using various imaging conditions. The origin of the twisting force to maintain the cholesteric ordering is also discussed.

The static structure factor and the first cumulant of the time correlation function in dynamic light scattering have been calculated for a regularly branched molecule with n shells of branching generations which are connected by chains of m repeating units per chain. Ideal flexibility for the chains is assumed. The dynamic scattering functions of these soft spheres show behavior significantly different from that of a hard sphere. The theory describes very satisfactorily the static and dynamic light scattering results obtained experimentally with polyvinyl acetate microgels. The possibility of determining the glass transition temperature of latex particles is briefly discussed.

The conformation and conformational change of wool keratin S- carboxymethylated low-sulphur proteins (SCMKA), which are α-helical fibrous proteins, have been investigated in aqueous solution by means of c.d. Comparisons of various methods proposed for c.d. analysis of protein secondary structure are made using least-squares curve-fitting of the observed c.d. spectra of SCMKA with a linear combination of the corresponding reference spectra of secondary structures. It has been found that (i) the most satisfactory results are obtained with the method13 which takes into account the β-turn contribution: (ii) SCMKA is 52–54% α-helical in water and has little β-form, (iii) the addition of n-propanol produces, even at higher concentrations of n-propanol, little chnage in spectra with respect to helical character in water; (iv) SCMKA undergoes a thermally-induced conformational transition from α-helix to random coil around 50 C; and (v) S- aminoethylated low-sulphur proteins with positively charged protecting groups are /_~50% α-helical in water, which is similar to SCMKA, showing that the protecting groups introduced in the low-sulphur proteins are little effect upon their conformation in water

The path-weighting generating function (pwgf) method is applied to calculate the hydrodynamic radii of the randomly crosslinked system as well as its monodisperse faction. Exactly the same relation is found for the z-average reciprocal effective hydrodynamic radius of the linear and the randomly crosslinked system as a function of the weight-average degree of polymerization DPw′, where b〈R h −1 〉 z = C(DP w ) − 1 2 with a constant C depending on the primary chain distribution. The weight-average reciprocal effective hydrodynamic radius, however, depends on the number average degree of polymerization and only moderately changes with crosslinking. The effective hydrodynamic radius of the monodisperse fraction is proportional to the quadratic root of the number of crosslinks. The technique is also applied to the dynamic scattering where formulae for the preaveraged and the non-preaveraged first cumulants are given.

The small-angle X-ray scattering (SAXS) method using a synchrotron radiation source was applied to the study of the self-aggregation process of tobacco mosaic virus protein (TMVP) at a concentration of 5.0 or 12.0 mg ml−1 in 50 m m or 100 m m -phosphate buffer (ionic strengths approx. 0.1 and 0.2, respectively) at pH 7.2 in the temperature region of 4.8 to 25.0 °C. This paper presents the results of static measurements of SAXS. Sedimentation velocity experiments were performed simultaneously under the same conditions. These results are qualitatively parallel to those of the SAXS measurements, although the size of stacked disks derived from the SAXS measurements is larger than that derived from the sedimentation experiments, suggesting a change in the equilibrium conditions in the centrifugal field. Qualitative analysis of the SAXS data with model simulation calculations implies that the aggregation of TMVP consists of two steps: (1) the aggregation of A-protein comprising a few subunits to form double-layered disks; and (2) the random polymerization of double-layered disks by disk-stacking. Increase in temperature, ionic strength or protein concentration induced TMVP to polymerize to form a double-layered disk or a quadruple-layered short rod with consumption of A-proteins, accompanied by a small number of multi-layered short rods. The SAXS results indicate that the A-protein and the multi-layered short rods are polydisperse with respect to size and shape, i.e. the mixture of A-protein, double-layered disks and multi-layered short rods coexists in the equilibrium state without pressure-induced partial dissociation of TMPV as observed during normal ultracentrifugation, and even under solution conditions in which the formation of double-layered disks or higher-order aggregates is favored.

Augmentation brutale des periodes longues a une certaine temperature au-dela de laquelle le degre de cristallinite re-augmente proportionnellement a la vitesse de chauffage. Presence de plusieurs endothermes dans la courbe de DSC, endotherme dont le 1 er intervient a la temperature mentionnee plus haut. Il est conclu que les cristaux originels fondent a chaque pic du thermogramme et que de nouveaux cristaux sont produits par recristallisation

The acidic aqueous solution of imogolite is proposed to be an ideal lyotropic system. No temperature dependence was marked on the two phase boundary concentrations (A and B points) of imogolite solutions as predicted by the theories of Flory and Onsager. A satisfactory quantitative agreement was observed with Onsager's theory. The polydispersity of rod lengths was found to shift the A point towards lower concentrations than expected from theory.

Imogolite, a natural product in the clay fraction of Japanese soil, was characterized through its dilute solution properties. Various methods were employed for this characterization, including viscosity, sedimentation, static/dynamic light scattering, and small angle X-ray scattering. All these measurements have revealed consistently that imogolite is represented by a rigid thin rod within the accuracy of available theories, where its repeat unit is composed of twelve gibbsite units. Since the evaluation of the chain length from the observed quantities depends on the molecular weight distribution, its effect was also considered where Mw/Mn ≈ 1,2 was estimated from the sedimentation profile.

The combinatorial theory of so‐called “trail‐weighting functions,” variously averaged over all trails in distributions of linear or branched molecules which are random (or at least lack long‐range correlations) has been described and exploited for calculation of physical parameters in previous papers. A trail‐weighting function is some arbitrary function φ(n) of the number of distinct trails of length n in the graph of a given molecule. By extending the use of univariate to bivariate generating functions, we here derive the moments of the distribution, the Stokes radii, and second virial coefficients for osmotic pressure and for light scattering of random f‐functional polycondensates. It emerges that the z‐average radius of gyration, the z‐average reciprocal Stokes radius, and the second virial coefficient of osmotic pressure are related to the weight‐average degree of polymerization, and the weight‐average radius of gyration and the weight‐average reciprocal Stokes radius to the number‐average degree of polymerization.

The method of Lagrange's expansion is applied to the bivariate generating function (‘trail-weighting generating function’) previously introduced for combinatorial calculation in polymer science. The wide range of applicability of this method is illustrated by calculation of the moments of the molecular weight distribution function, the Stokes radius and the particle scattering factor of random f -functional branched molecules which are monodisperse (i.e. of fixed molecular weight). The branched molecules in our system are composed of the (random) isomeric mixtures of all possible monodisperse f -functional molecules. This is chemically more realistic than assuming a fixed number of branching units in a molecule, as in Zimm and Stockmayer's, or Kurata and Fukatsu's model. In our model, each branch unit is not necessarily f -functional but the maximum functionality of a branch unit is f , while in an extreme case, the molecule will be linear. Also, the route of the combinatorial calculation is more systematic and appreciably simpler, so that this work helps to clarify the competing effects of branching and polydispersity.

A rapid temperature‐jump (T‐J) device was designed for the kinetic measurements of small‐angle x‐ray scattering from solutions of biological macromolecular systems. The dead time of the apparatus is reduced to a few hundred milliseconds. The structural change of biological macromolecules in solutions can be monitored in the time scale of a few hundred milliseconds by the synchrotron small‐angle x‐ray scattering with a combination of a CAMAC data‐acquisition system and the present T‐J apparatus.

The small-angle X-ray scattering was observed from β-casein micelles in 0.2 M phosphate buffer (pH 6.7) with varying temperatures. An oblate ellipsoid of a rigid core with a thin soft layer was proposed as a probable model of the β-casein micellar structure, according to the results of the model optimization with simple triaxial bodies. Here the axial ratio was found to decrease and the micelle to become spherical when the polymerization proceeds with temperature. The consistency of the present model was examined with the results of hydrodynamic measurements published previously.

Gelation was observed by time-resolved small-angle X-ray scattering and rheology on 10 mg/ml Ca-alginate gels prepared by in situ release of Ca 2+ from CaEGTA or CaCO 3 with total Ca 2+ concentration in the range 10–20 mM. This was carried out for alginates having a fraction of α- l -GulA (G) of F G =0.39 and 0.68, respectively, obtained by the selection of alginates isolated from two different brown algae, Ascophyllum nodosum and Laminaria hyperborea stipe. Correlation between the rheological data and SAXS data shows that a large fraction of the lateral association precedes the formation of a continuous network through the sample cell. Following the initial association of chain segments in junction zones, the analysis using two-component broken rod model indicates the formation of larger bundles, and that the relative weight of these bundles increases with increasing time. The molecular model for the bundles is proposed by associating 2–16 units (G-blocks) composed of 14 (1→4) linked residues of α- l -GulA in parallel according to the available crystallographic data. The storage modulus increases as the bundles composed of associated alginate chains grow during the gel formation. The gel elasticity is mainly sustained by single chains in the alginate sample with a low fraction of α- l -GulA. The alginates with a high fraction of α- l -GulA associate into thicker bundles which join to form a network. Here the gel elasticity seems to be due to the flexible joints between bundles, since the fraction of single chains is extremely low.

The β-1.3/1.6 glucan schizophyllan is a fungal polysaccharide that is known to suppress tumor growth. Thermoreversible, optically transparent gels of schizophyllan were obtained on addition of sorbitol to aqueous solutions of schizophyllan. Gel temperatures were independent of the history of sample preparation. The gelation process was followed by low-amplitude oscillatory shear and by static and dynamic light scattering. Power law behavior of storage modulus G′(ω) and loss modulus G″(ω) was found at the gel temperature with the exponent n=0.5. The static LS measurements showed a strong irregularity at the gel temperature. The intensity time correlation functions (TCFs) as measured by dynamic LS during the gelation process were transformed into the electric field TCFs, taking into account the heterodyne contributions. At the gel temperature which was estimated by rheology, DSC and static LS, no power law was found for the TCF. The angular dependence of the intensity TCF was measured and converted to the field TCF by use of a non-ergodicity treatment and by the heterodyne approximation, respectively. Both methods result in mean relaxation times that agree quite well. Two relaxation modes were found in the whole temperature range (above and below the gel temperature) indicating the existence of inhomogeneities in the gel.

Normal stresses and the shear stress in steady shear flow as well as the dynamic complex modulus are measured for dilute solutions of poly-n-butyl methacrylate in chlorinated diphenyl, in the range of concentration, 0.2∼1.0 wt.% and of molecular weight, 5.21×105∼2.30×106. The secondary normal stress was negligibly small compared to the principal one when the rate of shear was low. The steady shear compliance was proportional to the number of polymer molecules in the solution and its magnitude was of the order predicted from the spring-beads model theories. A relatively strong tendency to non-Newtonian effect was observed for the solutions with relatively high concentrations, and the reduced plot which was successfully performed for polystyrene solutions failed in this case at high rate of shear.