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Static and dynamic scattering properties of (a-b) diblock copolymer chains having different architectures are discussed in the framework of the random phase approximation (RPA). The case of a symmetric diblock (50/50) in a solvent satisfying the zero average contrast condition, in the semidilute regime, is considered in detail. We, in particular, calculate the scattering intensity and the relaxation times of linear rod-coil and once-broken rod copolymer chains and compare the results to those already known for classical linear diblock copolymers and to more recent results on ring diblock systems. Both static and dynamic scattering properties show that the microphase separation (MST) occurs for the symmetrical case at ( χ ΦN, q m R gt ) = (17.7, 2.9), (8.5, 2.2), and (8.2, 2.5) for ring coil-coil, linear rod-coil, and once-broken rod diblocks, respectively. These results are compared with those for linear diblock copolymers where the MST occurs at (10.5, 2).

Dynamic light scattering (DLS) and small-angle neutron scattering (SANS) are used to characterize the structure and dynamics of ternary solutions consisting either of rods or “hairy rod” polymers and polystyrene (PS) coils in a solvent composed of chloroform saturated with (

Dynamic light scattering (DLS) and transient electric birefringence decay measurements are performed on poly(γ-benzyl-α-l-glutamate) solutions over a wide concentration range. We interpret the primary dynamic decay rate always observed from dynamic light scattering experiments by extending the expression for the decay rate beyond the original limits of the mean field (DSO theory) theory of Doi, Shimada and Okano, (J. Chem. Phys. 1988, 88, 4070) to more general time and length scales. Our result, expressed as a power series in the scattering vector magnitude q, shows that, as expected, the primary decay rate from dynamic light scattering experiments at small q directly provides diffusion coefficients for mutual translation, whereas that at larger q contains contributions from both rotation and translation, including terms containing the translational anisotropy. The rotational relaxation times are obtained independently from the transient electric birefringence experiments and are used in our formula to ex...

Dynamic light scattering-photon correlation spectroscopy (PCS) has been used to study the dynamics of a 2311 base pair (bp) superhelical plasmid DNA in dilute and semidilute solutions. In dilute solution, translational and rotational/internal modes could be resolved. Assuming that the DNA is a rigid rod, the translational diffusion coefficient determined at infinite dilution gives cylinder dimensions consistent with a calculated length L of 230 nm and a diameter of 13.4 nm. If the rotational internal mode is interpreted as rotation of a rigid rod, the derived rotational diffusion coefficient is consistent with a shorter rod of a smaller length to diameter ratio. The dilute and semidilute regimes are clearly distinguished by a break in the concentration dependence of the mutual diffusion coefficient. The transition concentration, using the L given above, was found to lie at cL 3 between 3 and 5. In the semidilute regime, a slow mode was detected in addition to the main diffusion mode. The relative amplitude of the slow mode increases with increasing concentration until it is the dominant mode in the DLS frequency distribution. The slow mode frequency decreases with increasing concentration. The characteristics of the slow mode are not in accord with those of the slow mode predicted by the spinodal decomposition theory of Doi, Shimada, and Okano (DSO) for stiff rodlike polymers. The observed mode is consistent with the formation of aggregates in the semidilute regime. The mutual diffusion coefficient in the semidilute regime shows a linear concentration dependence, which is in qualitative agreement with the predictions of the DSO theory. The slope of this linear concentration dependence, however, differs markedly from the theoretical prediction assuming a concentration-independent self-diffusion coefficient. In addition, no deviation from quadratic scattering vector length dependence of the mutual diffusion mode, as predicted by the DSO theory, is observed. The rotational diffusion/internal relaxation frequencies appear to decrease with increasing concentration. However, the rather large scatter in the data (due to the relatively small contribution of this mode to the spectrum in the presence of the slow mode) prevented a quantitative comparison with existing theories

Dynamic light scattering (DLS) and static light scattering (SLS) nvere used to characterize the structure and dynamics of solutions of polystyrene of molecular weight 390 000 in 1,1,2,2-tetrachloroethane. Mutual diffusion coefficients were determined as functions of concentration and temperature. The diffusion virial coefficients were determined and compared to several theoretical predictions. The DLS intensity autocorrelation function was also carefully examined for the possible presence of fast modes in order to provide a comparison to polystyrene studied in ternary solutions including a rodlike polymer (paper 2)

The dynamics of macromolecules in ternary solutions consisting of a probe polymer (linear polystyrene (PS) of molecular weight 390 000), a matrix polymer (poly(n-hexyl isocyanate) (PHIC) of varying molecular weight and polydispersity), and a solvent (1,1,2,2-tetrachloroethane (TCE) or toluene) are studied using dynamic light scattering (DLS) with refractive index matching and, as supporting techniques, static light scattering and viscometry. PHIC is completely isorefractive in TCE at 75°C

The ionic strength dependences of the translational diffusion coefficient and the first internal mode relaxation time of monodisperse 2311 base pair relaxed circular DNA were studied by dynamic light scattering. Intensity autocorrelation functions were analyzed using the inverse Laplace transform method (CONTIN). Above the lowest scattering angle studied (33°), generally two peaks were found in the distribution of decay rates. The translational diffusion coefficient, corresponding to the slower of the peaks, at a low DNA concentration of 100 μg mL -1 was found to be (4.52±0.2)×10 -8 cm 2 s -1 , nearly independent of added NaCl from 1 to 0.001 M using a buffer of 10 mM Tris-HCl, 1 mM EDTA, pH 8

Five composite liquids consisting of the rigid rod polymer poly(γ-benzyl α,L-glutamate) and narrowly dispersed, spherical silica particles were studied in DMF by dynamic (DLS) and total intensity (TILS) light scattering. The diffusion constant of the spheres was measured by DLS. The effects of sphere size, rod length, and rod concentration on the diffusion of the spheres were investigated to probe the rod solution microstructure. Microviscosities as low as one-half of the solution viscosity were determined from the sphere diffusion constants near the rod concentration c * , which marks the onset of semidilute dynamics

The translational diffusion coefficient of a 2311 base pair circular DNA is in good agreement with the predictions of the circular wormlike cylinder model developed by Fuji and Yamakawa with a persistance length of 45 nm for DNA at 0.2 M salt. The longest internal relaxation time slows down when decreasing the ionic strength to 0.01 M. It was concluded from this result that the relaxation time is not dominated by the local stiffness of the chain. The overall picture of the difference between the dynamics of linear and circular wormlike chains is well represented by the free-draining Rouse-Zimm model with included stiffness

A new rod/sphere composite liquid was synthesized, characterized, and studied by dynamic light scattering (DLS). The liquid consists of coated silica spheres and poly(7-benzyl-a,L-glutamate) rods (PBLG) in dimethylformamide (DMF). Diffusion constants for spheres of radius 60.4 nm and PBLG rods of length 70 nm were measured by DLS in binary sphere/DMF and rod/DMF solutions as functions of concentration. The diffusion in the binary solutions is compared to that in ternary sphere/rod/DMF solutions at similar sphere and rod concentrations. These studies show that the diffusion of each species in the composite liquid can be measured simultaneously. No evidence was found for aggregation in either the binary or the ternary solutions. Changing the solvent to a mixture of DMF and pyridine allowed the spheres to be refractive index matched to the solvent, greatly decreasing their light scattering intensity. The diffusion of the rods in the composite liquid consisting of dilute spheres and rods of varying concentration was essentially the same as that in the binary rod/DMF solution. The transition between dilute and semidilute rod behavior was found to fall at 8.4 mg/mL or nL3 = 17, in the middle of the concentration range studied (2 < nL3 < 60.4). This value is similar to that found by Zero and Pecora for PBLG in dichloroethane. As the rod concentration increases, the product of the sphere diffusion constant and the solution viscosity remains constant, indicating that the sphere diffusion is consistent with the Stokes-Einstein equation. The dependences of the sphere diffusion constant and the solution viscosity on the rod concentration are well fit by a stretched exponential: DIDO = r)o/r) = exp (-0.16~~.~~). The dependence is comparable to that found from experiments using flexible coils as the background polymer. Theoretical predictions for rods, however, give a cO.5 dependence. The similar concentration dependence for silica spheres found in rod and coil solutions suggests that polymer flexibility alone does not account for the deviation from the theoretical predictions. Instead, rod-rod hydrodynamic interactions may play an important role in this deviation.

The molecular dynamic form factor for the Rouse-Zimm free-deaining Gaussian ring is calculated in a form which facilitates comparison with experimental scattering data. The relative contributions of the pure translation mode and various interanl modes are given. At zero time, the dynamic factor form reduces to the well known Casassa result for the static form factor. The differences in the dynamic form factors of linear and circular free-draining gaussian chain are discussed

Dynamic light scattering time correlation functions from dilute solutions of linear, monodisperse DNA restriction fragments, ranging in size from 367 to 2311 base pairs (molecular weight from 0.24 to 1.5 million), were measured at 20°C, in 100 mM NaCl, 10 mM Tris-HCl, and 1 mM EDTA (pH 8). The correlation functions were analyzed by using CONTIN, a constrained inverse Laplace transform program. At scattering angles of 16 and 22°, the correlation functions are consistent with single exponential decays representing the translational motion of the DNAs

Le but de la construction de ces 3 plasmides est la production de quantites suffisamment importants de fragments d'ADN de poids moleculaire varies servant de modeles tests en structure et dynamique moleculaire

Dynamique de polymere sans ecoulement, en solution diluee, a l'aide du modele de Kratky Porod

Reorientation d'une serie homologue de p-chlorobenzoates de n-alkyle dans un liquide homogene ou en solutions dans CCl 4

Emploi de l'interferometrie de Fabry Perot pour observer la diffusion dynamique de la lumiere depolarisee de p-dichlorophenylmethane et de ses melanges avec le PMMA, entre −4 et +98°C