Static and dynamic light scattering of a random coil polymer in rodlike polymer solution

We have studied ternary solutions of rodlike and random coil polymers in a common solvent. In these solutions, the rods scatter weakly, and almost all scattering comes from the coil component. From light scattering measurements, we gained information about the thermodynamic and hydrodynamic properties of the coil in rodlike polymer solutions.     

Static and dynamic light scattering in turbid suspensions

The application of static and dynamic light scattering to many colloidal systems of practical interest has often been considered too complicated due to strong multiple scattering. There are two new approaches to overcome this problem. One of them aims at suppressing contributions from multiple scattering using novel cross‐correlation schemes. While this relies on the suppression of multiple scattering, the so‐called diffusing wave spectroscopy (DWS) works in the limit of very strong multiple scattering. DWS can be used for the characterization of dynamic and static properties of colloidal systems on a large range of time and length scales ranging from a few Ångstroms to hundreds of nanometers. We demonstrate that a wealth of information can be obtained from these methods on the structure, dynamics, interaction effects, stability, aggregation, and sol‐gel transition in colloidal dispersions.     

Depolarized light scattering from critical polymer blends

Depolarized light scattering of binary polymer blends in disordered state near the demixing critical point is considered both theoretically and experimentally. It is shown that the depolarized scattering in such systems is predominantly due to double scattering processes induced by composition fluctuations. For long enough polymer chains, this scattering is stronger than the contribution from intrinsic anisotropy fluctuations. The general equation for the static and dynamic double scattering function is obtained in terms of the system structure factor. The scattering functions are calculated both analytically and numerically (dynamic part) for polymer blends. We found that the depolarized intensity depends on the polymerization degree N and the relative distance from the critical point τ = 1 – χ*/χ (where χ is the Flory‐Huggins interaction parameter and χ* its critical value) as I_vh ∼︁ N²/τ², which is in good agreement with the experimental data. It is also shown that the dynamic scattering function is decaying non‐exponentially. We calculate the relaxation rate and the non‐exponentiality parameter as functions of the scattering angle and τ. These theoretical predictions are compared with experimental data for three chemically different blends.     

Static and dynamic light scattering study of fluorinated polymer colloids with a crystalline internal structure

The light scattering properties of polymer colloids made of polytetrafluoroethylene with added copolymers are described in some detail. The particles possess a partially crystalline internal structure which makes them optically anisotropic, and consequently gives rise to a strong depolarized component in the scattered light intensity. We present a complete theory of static and dynamic light scattering which includes the effects of polycrystallinity, of optical polydispersity, and of interparticle interactions. We also discuss applications to surfactant adsorption studies, to sedimentation experiments and to fractal aggregation processes     

Static light scattering study of complex formation between protein and neutral water-soluble polymer

Complex formation of poly(N-isopropylacrylamide) (PNIPA) having a weight-average molecular weight of 1,720,000 g/mol with human serum albumin (HSA), ovalbumin (OVA) and lysozyme (LYZ) was studied in an aqueous medium containing 0.01 M NaCl and adjusted to pH 3. The polymer–protein mixtures at different molar ratios (r_m) were examined by static light scattering (SLS). The analysis of SLS data using our own approach [Kokufuta et al., Langmuir 15 (1999) 940; Biomacromolecules 4 (2003) 728] showed that the molecular weight of each resulting complex is smaller than that of the interpolymer complex composed of two polymer chains plus one protein. This indicates the formation of an intrapolymer complex in all the polymer–protein systems studied. Thus, at each r_m we calculated the number of bound proteins per polymer, the value of which was OVA > HSA > LYZ in order. These results were compared with the hydropathy profiles of each protein which are a good tool for obtaining an information about distribution of hydrophobic and hydrophilic segments in a protein. It has become apparent that the hydrophobic interaction between polymer and protein plays an important role in the intrapolymer complex formation.     

Fluorescence and dynamic light scattering studies of niosomes-membrane mimetic systems

Niosomal vesicles are more stable than liposomal vesicles due to higher chemical stability of surfactants compared to phospholipids. Niosomes have been prepared from Span20, Span80, Tween20 and Tween80. Fluorescence resonance energy transfer studies have been performed in these systems to determine donor-acceptor distances. It has been found that the fluorescence resonance energy transfer efficiency is better in niosomes compared to micelles. The formation of niosomes is guided by the hydrophile-lipophile balance value of the nonionic surfactant.     

Neutron and light scattering studies of polymer blends and block copolymers

The structure of compatible polymer mixtures and its temperature dependence can be well described in many cases by the mean-field approximation. Deviations with regard to the temperature dependence of the correlation length of concentration fluctuations can be explained by taking into account the spatial structure of the interaction potential. Concentration fluctuations and the microphase separation in diblock copolymers are in good agreement with theories based on the random phase approximation. In the two-phase region the temperature dependence of the scattered X-ray or neutron intensity is governed by the difference in the thermal expansion coefficients of the two components of the diblock copolymer. Photon correlation spectroscopy (PCS) yields valuable information on the concentration dependence of the mutual diffusion coefficient D_AB.     

Studying the curing of epoxyamine mixtures via dynamic light scattering and differential scanning calorimetry

The curing of epoxy oligomers with different structures and reactivity using an aliphatic amine curing agent was studied and quantitatively characterized by the methods of dynamic light scattering and differential scanning calorimetry. The presence of disperse phase in the initial reagents, as well as in the reacting systems is established. It is shown that the particles of the disperse phase are involved in the process of curing even in the early stages. By changing the width of the devitrification region, the change in the molecular homogeneity of epoxyamine systems during curing is estimated.     

Classical light scattering studies on structure formation in polymer solutions

The scattered light is very sensitive to the presence of supermolecular structures in polymer solutions, offering the possibility to study structure formation in situ by classical light scattering and to characterize the generated particles. An improved analysis of light scattering data yields information on the structure type, polydispersity of the systems, particle mass and size as well as the degree of swelling. The flocculation process of ampholytic modified poly(acrylonitrile) was investigated in dependence on the pH-value and the content of different salts in the solvent. Results obtained give a deeper insight into the flocculation mechanism.     

Dynamic light scattering from ternary polymer blends: critical behavior and bicontinuous microemulsions

We have used dynamic light scattering to study the dynamics of ternary polymer blends consisting of poly(dimethylsiloxane) (PDMS) and poly(ethylethylene) (PEE) homopolymers and a PDMS‐PEE diblock copolymer nearly symmetric in composition. The intensity autocorrelation functions for the binary blend are single‐exponential, and the associated correlation length ξ scales with reduced temperature ϵ in accordance with the Ising universality class (i.e., ξ ∼ ϵ^−ν, with ν = 0.63). An addition of copolymer depresses the critical temperature, but also increases the magnitude of ν. For compositions within the microemulsion channel, ξ exhibits a distinct maximum with decreasing temperature, near the Lifshitz line obtained from the static structure factor. For a particular composition, there is a “re‐entrant” microemulsion, as the system passes into and then out of the phase‐separated region upon cooling.     

Composition determination of binary polymer mixtures by size exclusion chromatography with light scattering detection

<正>Base on the principle of absolute quantification of size exclusion chromatography(SEC),a light scattering(LS) detector coupled with a concentration detector(refractive index detector) is utilized to determine the compositions of complicated binary mixtures.A theoretical analysis predicts that the response factors for both LS and RI detectors are linear functions with the composition of any specified polymer mixtures in the binary polymer mixtures.Two pairs of complicated binary mixtures were used to test the theory mentioned in the present paper,and the experimental results show an excellent accordance with the theory.     

Self-aggregation of mixtures of oppositely charged polyelectrolytes and surfactants studied by rheology, dynamic light scattering and small-angle neutron scattering

In this study, the phase behavior, structure and properties of systems composed of the cationic, cellulose-based polycation JR 400 and the anionic surfactants sodium dodecylbenzenesulfonate (SDBS) or sodium dodecylethoxysulfate (SDES), mainly in the semidilute regime, were examined. This system shows the interesting feature of a very large viscosity increase by nearly 4 orders of magnitude as compared to the pure polymer solution already at very low concentrations of 1 wt%. By using rheology, dynamic light scattering (DLS), and small-angle neutron scattering (SANS), we are able to deduce systematic correlations between the molecular composition of the systems (characterized by the charge ratio Z=[+(polymer)]/[?(surfactant)]), their structural organization and the resulting macroscopic flow behavior. Mixtures in the semidilute regime with an excess of polycation charge form highly viscous network structures containing rodlike aggregates composed of surfactant and polyelectrolyte that are interconnected by the long JR 400 chains. Viscosity and storage modulus follow scaling laws as a function of surfactant concentration (η~c(s)(4); G(0)~c(s)(1.5)) and the very pronounced viscosity increase mainly arises from the strongly enhanced structural relaxation time of the systems. In contrast, mixtures with excess surfactant charges form solutions with viscosities even below those of the pure polymer solution. The combination of SANS, DLS, and rheology shows that the structural, dynamical, and rheological properties of these oppositely charged polyelectrolyte/surfactant systems can be controlled in a systematic fashion by appropriately choosing the systems composition.     

Antiferroelectric behaviour of achiral mesogenic polymer mixtures

X-ray structure determination and pyroelectric and piezoelectric measurements have been carried out on mesogenic mixtures composed of achiral side chain polymers and their monomers. Certain mixtures show antiferroelectric polarization hysteresis loops in the mesophase which was shown to be a bilayered smectic C, while the two components of the mixtures taken alone show no antiferroelectricity. The results obtained on the polymer-monomer mixtures are interpreted in terms of the smectic C structure with alternating tilt which, from a symmetry viewpoint, is allowed to be antiferroelectric. The antiferroelectric mixtures, on being cooled to the glassy state under a d.c. electric field applied, reveal high pyroelectric coefficients with prospects for application as IR detectors.     

Temperature behaviour of a liquid crystal comb polymer: Light scattering and noise of the scattered light

Measurements of the intensity of the monochromatic light transmitted through and scattered by a comb polymer with a polyacrylamide main chain were performed between room temperature and the isotropization temperature of the polymer. The stationary noise of the light scattered at low angle was measured in the same temperature interval. The transmitted intensity is observed to increase strongly above the smectic S_I2-S_c2 transition, where the intensity of the light scattered at low angles is maximized. The power dissipated by the molecular fluctuations dramatically increases above the transition between the two smectic phases. The spectral density curves display a Lorentzian character only below the S_I2-S_c2 transition. At higher temperatures, a more complex frequency behaviour of the stationary noise spectra is observed. Such a behaviour is interpreted in terms of a model explicitly invoking the effect of the Brownian movement of segments of the main chain (backbone) of the polymer on the side chain fluctuations. The parameters governing the Brownian movements of both main and side chains, and their evolution with temperature, are determined and discussed in the light of a simple structural model.     

Synthesis,static, and dynamic light scattering studies of soluble aromatic polyamide

Aromatic polyamide was synthesized via condensation polymerization of 4‐aminophenyl sulfone (APS) with isophthaloyl chloride (IPC) using N,N‐dimethyl acetamide (DMAc) as a solvent under anhydrous conditions. The purified aramid was studied by laser light scattering (LLS) in dimethyl sulfoxide (DMSO), a thermodynamically good solvent at 20°C. Static and dynamic light scattering studies permitted to determine the weight average molecular weight , radius of gyration , second virial coefficient A₂, the hydrodynamic radius R_H, and the diffusion coefficient D. Light scattering experiments were conducted at five concentrations ranging from 0.27 to 2.5 g/L. LLS measurement is also a very useful technique to study the aggregation or association in a polymer system as long as the large “clusters” are reasonably stable in time. The intensity autocorrelation function obtained on the quasi‐elastically scattered light showed a simple diffusive relaxation mode. The ratio of radius of gyration to the hydrodynamic radius, i.e. ～ 1.3 indicates that the polyamide chain has coil conformation in DMSO at 20°C. Copyright © 2008 John Wiley & Sons, Ltd.     

Evaluation of the dynamic properties of polymer latex particles interacting with quartz interface by evanescent wave dynamic light scattering

The diffusion behavior of polymer latex particles in dispersion near the quartz interface has been estimated by evanescent wave dynamic light scattering (EVDLS) technique. The diffusion coefficient of the particles was measured as a function of the distance between the particle and interface. The apparent diffusion coefficient estimated by EVDLS was small for particles near the interface and increased upon increasing the distance from the interface, and then saturated at a certain value which is close to the value expected for free-motion. The range of the distance over which diffusion was affected by interaction with the interface depended on the added salt concentration. This means that the diffusion of the particle is influenced by an electrostatic interaction between the particle and quartz interface in addition to the hydrodynamic effect near the wall. This range was found to be more than 800?nm at 0?M salt condition but about 400?nm at 10^-4 and 10^-3?M salt conditions. Hence it is appropriate to say that the hydrodynamic effect reaches up to 400?nm and the electrostatic effect is longer ranged, more than 800?nm, for the system studied here. The EVDLS technique is a very powerful tool for quantitative estimations of the dynamic behavior of the particle near the interface and for estimation of the range where the wall effect is dominant. EVDLS will give us an answer to the question of “where is the ‘interface’ and where is the ‘bulk’?”.     

Dynamic light scattering method of polymer solutions

The main features of dynamic light scattering are briefly outlined. The capability of this method to characterizing molar mass distributions and to distinguishing different molecular architectures is demonstrated with some examples. Special attention is given to the question of internal mobility and the spectrum of relaxation times. Recent results on asymptotic behavior are presented and discussed. Scaling behavior of the first cumulant with respect of space and of the time correlation function with respect of time (shape function) is found. All examples studied so far demonstrate the dynamic scaling of Zimm-Rouse chains, but the prefactors strongly depend on branching and crosslinking.     

Diffusion of spherical micronetworks in polymer diluent systems and melts studied by dynamic light scattering techniques

Spherical polystyrene (PS) micronetworks can be prepared in microemulsion with bulk radii of 5–60 nm and different cross-linking densities. The diffusion of these PS spheres has been studied in polymer diluent systems ranging from dilute solutions to plasticized melts by using forced Rayleigh scattering and photon correlation spectroscopy. On increasing the PS concentration, a colloid glass transition is observed at a volume fraction Φ_C ≈ 0.64 of the swollen spheres. At higher concentration inside the “colloid glass” state the sphere diffusion is slowed down and becomes very complex but can be observed up to the limit of a melt of collapsed spheres.     

Depolarized light scattering studies on single-phase mixtures of dissimilar polymers: Evidence for local ordering

Depolarized light scattering measurements on single-phase mixtures of dissimilar polymers, poly(methyl methacrylate) (PMMA)/poly (acrylonitrile-co-styrene) (SAN, AN content = 15 wt %) and PMMA/poly (vinylidene fluoride) (PVDF) were carried out. The effective mean-square optical anisotropy γ² of the mixtures was found to be much higher than that estimated by the simple additivity of γ² of component polymers. From the deviation, the order parameter (1 + J₁₂) was estimated to be in a range of 2–13, depending on the blend composition. This suggests local ordering in the single-phase mixtures, i.e., nematic alignment of the locally stretched dissimilar chains. In contrast, the deviation was slight in the polymer/solvent systems, SAN/MMA (monomer) and PVDF/butanone. The degree of ordering decreased with increasing temperature. T. The Specific interaction evidenced by FTIR spectroscopy exhibited a similar temperature dependence. Thus, local ordering seems to be induced by specific interactions and chain connectivity. The temperature dependence of J₁₂ was successfully described by the Landau-de Gennes theory; J ∞ (T + T₀)/ T, T₀ being the isotropic-nematic transition temperature, as in the case of liquid crystals.