Osmotic compressibility in dilute polystyrene‐cyclohexane and polystyrene‐methylcyclohexane solutions: Correlation of polystyrene virial coefficients with solvent quality

Osmotic compressibilities were determined as a function of temperature for solutions of polystyrene in cyclohexane and methylcyclohexane by static light scattering, the measurements extending well below the theta temperature, T = θ. Virial coefficients extracted from the data are compared with literature values obtained by light scattering, membrane osmometry, and phase equilibrium measurements, and successfully correlated over wide ranges of molecular weight, temperature, and solvent quality. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 184–196, 2001     

Aggregation behavior of polystyrene‐b‐poly(ethylene/butylene)‐b‐polystyrene triblock copolymer in N‐methylpyrrolidone

Solution property of hydrogenated polystyrene‐b‐poly(ethylene/butylene)‐b‐polystyrene triblock copolymer (SEBS copolymer) was studied by using static light scattering and dynamic light scattering for cyclohexane and N‐methylpyrrolidone (NMP) solutions. From the values of dimensionless parameters ρ, defined as the ratio of radius of gyration 〈S²〉^1/2 to hydrodynamic radius R_H, and solubility parameters, SEBS copolymer proved to exist as single chain close to random coil in nonpolar cyclohexane, whereas aggregate into the core‐shell micelle consisting of poly(ethylene/butylene) (PEB) core surrounded by PS shell in polar NMP. The core‐shell micelle formed in NMP is composed of 65 polymer chains, having three times larger average chain density (d = 0.12 g cm^?3) than a single polymer chain (d = 0.04 g cm^?3) in cyclohexane. The comparison with the aggregation behaviors in other solvents demonstrated that the aggregate compactness of the copolymer depended largely on solvent polarity, resulting in formation of the highly dense PEB core (R_c = 4.5 nm) and the thick PS shell (ΔR = 22.9 nm) in high‐polar NMP. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 588–594, 2010     

Hydrodynamic radius of polyethylene glycol in solution obtained by dynamic light scattering

In order to compare the size characterizations in poly(ethylene glycol) (PEG) obtained by dynamic light scattering (DLS) and small angle neutron scattering (SANS), DLS experiments were performed in various PEG solutions to ascertain the hydrodynamic radius. Data from the experiments were analyzed by using a method to eliminate effects of PEG aggregation on dynamic correlation functions. The results of the analysis were then compared to the radii of gyration reported from SANS experiments. The relation between the hydrodynamic radius, obtained by DLS, and the radius of gyration, obtained by SANS, in PEG in solution was found to be in agreement with a previously obtained relation for PEG, where the radius of gyration was found by static light scattering.     

Electroptical and dynamic properties of sulfonated polystyrene molecules and their associates in chloroform

The behavior of sulfonated PS containing 0.5, 1.35, 2.6, and 5.8 mol % of sodium sulfonate groups in chloroform solutions has been studied by static and dynamic light scattering, viscometry, and electric birefringence. The molecular mass of ionomers is measured, and their translational diffusion coefficient, intrinsic viscosity, and free relaxation times are estimated. It has been shown that association in solutions of ionomers containing more than 1.35 mol % of sodium sulfonate groups proceeds according to the open association model. Analysis of autocorrelation functions of scattered light intensity and electric birefringence decay makes it possible to determine translational diffusion coefficients and relaxation times for individual ionomer molecules, their pair associates, and higher multiplicity associates. With an increase in the fraction of sodium sulfonate groups, the hydrodynamic radius of individual ionomer molecules decreases from 8 to 5.8 nm, while the ratio between the hydrodynamic radius of pair associates and individual sulfonated PS molecules increases.     

Dynamic light scattering from non-entangled wormlike micellar solutions

The fuzzy cylinder theory, originally proposed for conventional polymer solutions, was applied to wormlike micellar solutions to take into account effects of the intermicellar collision and hydrodynamic interaction on the self-diffusion of wormlike micelles in solution at finite concentrations. Previously reported apparent hydrodynamic radius data obtained by dynamic light scattering for non-entangled wormlike micelles formed in aqueous solution by non-ionic surfactants, polyoxyethylene monoalkyl ethers C(i)E(j), were analyzed by this theory to estimate the persistence length q of the wormlike micelles. The results of q estimated were consistent with those obtained from radius of gyration data obtained by static light scattering.     

A COMPARATIVE STUDY OF CHAIN DYNAMICS OF DI-AND TRI-BLOCK COPOLYMERS IN SEMIDILUTE SOLUTION IN A NON-SELECTIVE SOLVENT

The chain dynamics of a pair of diblock poly(styrene-b-butadiene) (PS210-b-PB960) and triblock poly(styrene-b-butadiene-b-styrene) (PS200-b-PB1815-b-PS200) copolymers in both dilute and semidilute toluene solutions has been comparatively studied by dynamic laser light scattering. As expected, the mutual diffusion of individual chain changes into a fast cooperative diffusion of the chain segments (“blobs“) between two neighboring entanglement points for both the copolymers as the solution changes from dilute to semidilute. Further increases of the concentration lead to a second slow relaxation mode. For the triblock chains, there exists an additional middle relaxation between the fast and the slow modes.with 0.33 ＜α＜ 0.44, much smaller than 0.75 predicted or 0.72 observed for linear homopolymer chains in good solvent. It implies that the solvent quality of toluene for PB might not be as good as that for PS. Due to such a difference in solubility, it is reasonable to speculate that the PB and PS blocks are transiently segregated in semidilute solution. The relaxation of these transient PB and PS richer domains leads to the observed slow relaxation. Such a speculation is supported by the appearance of an additional slow relaxation mode in the study of polyisoprene-b-polystyrene-b-polyisoprene in semidilute solution in cyclohexane, a non-selective solvent, in which we alternated the solubility difference by a variation of the solution temperature.     

Dynamics of end-grafted polystyrene brushes in theta solvents

The dynamics of the concentration fluctuations in end-grafted polystyrene brushes in a theta solvent (cyclohexane) are probed by evanescent wave dynamic light scattering at different wavevectors q and temperatures. When the solvent quality changes from marginal to poor, the relaxation function C(q, t) exhibits strong effects as compared with the smooth variation of the brush density profile. From a single exponential above 50 °C, C(q, t) becomes a two-step decay function. The fast decay is still assigned to the cooperative diffusion albeit slower than in the good solvent regime whereas the slow nonexponential and nondiffusive process might relate to microsegragated and/or chain dynamics in the present polydisperse brush. The relaxation function of the present three brushes with different grafting density reveals similarities and disparities between wet brushes and semidilute polymer solutions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3590–3597, 2006     

Structure and dynamics of solutions of a polystyrene–polybutadiene pentablock copolymer in a styrene‐selective solvent

We have examined solutions of a polystyrene–polybutadiene pentablock copolymer in 1,4‐dioxane, a slightly selective solvent for polystyrene and a θ solvent for polybutadiene, with static light scattering (SLS), dynamic light scattering (DLS), and small‐angle neutron scattering (SANS). The SANS data have been analyzed with the Percus–Yevick model to represent the scattering from interacting cores, approximated as hard spheres, and with a Lorentzian function to represent the scattering from unassociated and associated polymer chains. The SANS data at 25 °C clearly reveal interacting domains, approximately 6 nm in radius, formed by the association of the insoluble polybutadiene block in the 20% sample. The 4% sample does not show such domains, whereas the 7% sample represents an intermediate situation, with both unassociated polymer and associated polymer. At higher temperatures, the domains dissolve. The DLS data for samples with concentrations of 2–22% show two diffusive modes: a fast mode corresponding to the cooperative dynamics of concentration fluctuations and a slow mode corresponding to the diffusion of clusters. The large length‐scale heterogeneities, indicated by the strong angular dependence of SLS, implies that the small microdomains of about 10–15 polybutadiene blocks are bridged by the polystyrene chains, forming large aggregates with randomly distributed crosslinks on length scales much larger than the domain size. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2807–2816, 2002     

建筑用梳形共聚物分散剂溶液行为的光散射研究

采用激光光散射研究了一种主链为聚丙烯酸侧链为聚乙二醇的梳形共聚物分散剂的一些溶液行为.从静态光散射得出了较为合理的表观重均分子量、均方旋转半径等参数.动态光散射给出了流体力学半径分布及其角度和浓度依赖性.结合静态和动态光散射,上述梳形共聚物分散剂在溶液中的构象也得到初步的表征.通过与描述梳形聚合物的Gay-Raphae模型进行比较表明,这类梳形共聚物溶液在低盐离子和低pH值条件下存在聚集行为,形成以PAA主链为核PEG为壳层的类胶束聚集.     

The effect of nanoparticle nonuniformity on the ratio of gyration and hydrodynamic radiuses

The ratio of the radius of gyration, obtained by static light scattering, and the hydrodynamic radius, obtained by dynamic light scattering, are routine experimental techniques for the assessment of nanoparticle shape. The potential effect of particle nonuniformity is mostly not considered. In this communication, we demonstrate that, even with medium particle nonuniformities, it is advisable to apply appropriate corrections. The values of the correction factors are offered in a diagram for various particle shapes, and two types of particle-size distributions and their widths.     

Behavior of heterogeneous macromolecular structures Part I: Microgels and coated microgels

Homopolymeric microgels composed of PMMA were prepared by emulsion polymerization in the presence of 0.5 % 1,4-butanediol divinylether (BVE) in an aqueous medium followed by careful removal of the soap. The microgels were coated with polystyrene (PS) by anionic grafting of living PS chains onto the surface. Both types of microgels were characterized by GPC and by static and dynamic light scattering in several solvents. A special model consisting of a hard core and a seam of dangling chains has been developed and applied to interpreting the light scattering data from the various solvents. The model gives consistent results, e. g. the core radius agrees well with the radius of gyration. In the coated microgels a strong expansion of the core as a result of the PS/ PMMA incompatibility is observed.Dedicated to Prof. Dr. H.-G. Kilian on the occasion of his 60th birthday.     

Hydrodynamic Radius Characterization of a Vinyl-Type Polynorbornene by Size-Exclusion Chromatography with a Static and Dynamic Laser Light Scattering Detector

Both absolute molecular weight and molecular sizes (radius of gyration and hydrodynamic radius) of a vinyl-type polynorbornene eluting from size-exclusion chromatography columns were determined by combined with a static and dynamic laser light scattering detector. The hydrodynamic radius of polymer fraction eluting from size-exclusion chromatography columns was obtained from dynamic laser light scattering measurements at only a single angle of 90° by introducing a correction factor. According to the scaling relationship between molecular sizes and molecular weight and the ratio between radius of gyration and hydrodynamic radius, the vinyl-type polynorbornene took a random coil conformation in 1,2,4-trichlorobenzene at 150 °C.     

Neutron scattering in polymer gels at the theta temperature

Small angle elastic neutron scattering was performed on three polystyrene networks swollen to equilibrium in cyclohexane at the theta temperature. Comparison of the SANS spectra with similar measurements in uncross-linked solutions reveals that in the intermediate Q region the gels behave like solutions of lower concentration than the equivalent solutions. We assume that the gel spectra are composed of a static component plus a dynamic, or solution-like part. By a suitable fitting procedure, the former can be estimated, yielding the mean square static concentration fluctuation <Δφ²> generated by cross-linking contraints in the gel. Independent measurement of the swelling pressure of these gels permits an estimate to be made of the scattering intensity I(Q=0) of the dynamic part of the spectrum. Plausible agreement is found between the macroscopic and microscopic estimations of the osmotic compressibility if allowance is made for the concentration polydispersity in the gels.     

Miscible blend dynamics and the length scale of local compositions

We consider the influence of a local, or effective, composition on dynamics in the miscible polymer blend PEO/PMMA. Quasielastic neutron scattering in combination with deuterium labeling is employed to determine characteristic relaxation times of the PEO component over spatial scales from 3 to 10 Å. Information about the distribution of relaxation times is obtained indirectly from the stretching parameters in a stretched exponential fit. We examine the behavior of these parameters with spatial scale and temperature, finding that their variation supports a distribution of PEO mobility in the blend which is far wider than pure PEO and narrows with decreasing temperature for small spatial scales. This is linked to the concept of local compositions defined over varying spatial scales, and indicates that the concept of a local composition, linked to PEO dynamics, is important in this system. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2914–2923, 2005     

Shear-sensitive chain extension of dissolved poly(ethylene oxide) by aluminate ions

The phase behavior of poly(ethylene oxide) (PEO) in aqueous salt solutions has been studied many times but rarely for solution conditions relevant to the hydration process of cement, where PEO's interactions with surrounding ions modulate its application as both plasticizer and strength-building additive. Here, the conformation, that is, coil size, of PEO was examined in aqueous solutions in the presence of sodium-, calcium- and aluminum-containing salts. Ion-induced conformational changes for a model linear PEO were mostly unremarkable and consistent with past reports. However, trends for aluminum-containing ions, which predominantly occur in water at neutral and basic pH as the monovalent hydroxo-aluminate anion Al(OH)₄⁻, were different: either present as the sodium or calcium salt, PEO's hydrodynamic radius determined by dynamic light scattering was approximately 30% larger than determined by intrinsic viscosity. The intrinsic viscosity was similar to that measured in the presence of simpler monovalent anions. We hypothesize that aluminum containing ions weakly couple the model polymer's hydroxyl end groups (present at just one chain end), creating polymeric aggregates sensitive to disruption by shearing. Supporting our argument, the hydrodynamic radius determined by dynamic light scattering dropped to the intrinsic viscosity value after hydroxyl groups were converted to methoxy groups.     

Depolarized light-scattering spectroscopy and polymer characterization

Light scattering has long been established as a technique for measuring the molecular weight and radius of gyration of polymer molecules. Depolarized light scattering can be studied accurately with lassers. The theory of static and dynamic depolarized light-scattering spectroscopy is presented and illustrated with two examples of novel particles in solution. From the static intensity measured as a function of angle, the length of rod-like molecules can be evaluated. More complicated geometrical measures are obtained in the eneral case. From the dynamic light scattering, the translational self-diffusion coefficient and the rotational diffusion coefficient are obtained. These quantities can be interpreted in terms of a major semi-axis length and an axial ratio for the molecule or particle by using the Perrin equations.     

Structure and dynamic properties of colloidal asphaltene aggregates

The abundant literature involving asphaltene often contrasts dynamic measurements of asphaltene solutions, highlighting the presence of small particle sizes between 1 and 3 nm, with static scattering measurements, revealing larger aggregates with a radius of gyration around 7 nm. This work demonstrates the complementary use of the two techniques: a homemade dynamic light scattering setup adapted to dark and fluorescent solutions, and small-angle X-ray and neutron scattering. Asphaltene solutions in toluene are prepared by a centrifugation separation to investigate asphaltene polydispersity. These experiments demonstrate that asphaltene solutions are made of Brownian colloidal aggregates. The hydrodynamic radii of asphaltene aggregates are between 5 and 10 nm, while their radii of gyration are roughly comparable, between 3.7 and 7.7 nm. A small fraction of asphaltenes with hydrodynamic and gyration radii around 40 nm is found in the pellet of the centrifugation tube. The fractal character of the largest clusters is observed from small angle scattering nearly on a decade length scale. Previous results on aggregation mechanisms are confirmed ( Eyssautier, J., et al. J. Phys. Chem. B 2011 , 115 , 6827 ): nanoaggregates of 3 nm radius, and with hydrodynamic properties also frequently illustrated in the literature, aggregate to form fractal clusters with a dispersity of aggregation number.     

Block copolymers with Zwitterionic groups at specific sites: Synthesis and aggregation behavior in dilute solutions

Well‐defined linear diblock and triblock copolymers of styrene and isoprene, nearly symmetric in composition, with one or two sulfobetaine associogenic groups at the ends of the polymer chain or the junction points between blocks, were synthesized by anionic polymerization high‐vacuum techniques. The synthetic strategy used the combined initiation of polymerization with 3‐dimethylaminopropyllithium, living end‐capping with 1‐(4‐dimethylaminophenyl)‐1‐phenylethylene, and postpolymerization reaction with cyclopropanesultone. The association behavior of these macromolecules in dilute solutions in the nonpolar solvent CCl₄, good for both blocks, was studied by a number of methods, including static and dynamic light scattering and viscometry. The number and position of the associogenic groups dramatically influenced the association behavior of these model block copolymers. The end‐functionalized samples formed larger aggregates than the junction‐point‐functionalized ones. The difference was attributed to stronger excluded volume effects when the zwitterion group was located within the chain than when the group was at the chain end(s). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3791–3801, 2000     

Dynamic light scattering of semidilute hydrophobically modified alkali‐soluble emulsion solutions with different lengths of poly(ethylene oxide) spacer chain

Semidilute solutions of hydrophobically modified alkali‐soluble emulsion (HASE) were examined by dynamic light scattering and rheological techniques. For the model polymer without associative macromonomer, two q² dependent diffusional modes were detected in the decay time distributions. With increasing hydrophobicity of the associative macromonomer, the narrow fast peak was substituted by a shallow broad peak and only one q² dependent slow mode could be accurately detected, which indicated that the heterogeneity of these associated clusters increases with increasing carbon number. The bulk steady‐shear viscosity exhibits similar results to the diffusion coefficients of the aggregate observed from light scattering measurements. The length of poly(ethylene oxide) (PEO) spacer chain alters the solution properties as well as the associative cluster structure. With increasing length of PEO spacer chain, intramolecular association was substituted by intermolecular association. For EO segment larger than 32 units, intramolecular association dominates, where the formation of HASE aggregates is controlled by the balance of electrostatic repulsion and hydrophobic attraction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3288–3298, 2005     

Critical behavior of trifunctional randomly branched polycyanurates

The behavior near the gelation threshold of trifunctional randomly branched polycyanurates is studied by static and dynamic light scattering. By static measurements the critical exponents γ, σ and η were obtained, which describe the divergence of the weight average (M_w) and the cutoff (M*) molecular weights and the radius of gyration (R_g) respectively. All these independently measured exponents together with τ, characterizing the power law behavior of the molecular weight distribution and measured by size exclusion chromatography coupled with light scattering, confirm the predictions of the three-dimensional percolation theory. With the help of size exclusion chromatography coupled with a light scattering and a viscosity detector, a fractal dimension D = 2.24 is obtained. On the other side, from the corresponding exponent for the whole unfractionated samples a fractal dimension D = 2.21 results, using a theory of Daoud. This suggests that the fractal dimension of the polycyanurates in dilute solution lies between the theoretical predictions D = 2.5 for the unswollen and D = 2.0 for the completely swollen state. Furthermore, it is shown by dynamic light scattering that the power law behavior over some decades in time of the time autocorrelation function and the divergence of the mean relaxation time are characteristics of the gelpoint. The development with increasing reaction time of the time correlation function of the gelling system from the pregel through the gelpoint into the gel state is analyzed quantitatively by a hybrid of a stretched exponential and a power law function.