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Stable polymeric nanoparticles were prepared by self-assembly of poly(ethylacrylic acid) homopolymers. The mechanism of the self-assembly is based on heating a solution of thermoresponsive partiall...

It is shown that very pure sodium hyaluronate (HA) contains small amounts of strongly scattering impurities not detectable on mass scale by refractometric detection, but clearly detectable using low angle light scattering detection during a static bulk light scattering experiment. Size filtration of its solutions does not remove these impurities, only reduces their amount depending on filter porosity. Complete removal of these particle impurities, independent of filter porosity, is achieved by hydrophobic adsorption on hydrophobic filter membranes. Using 0.1 M NaCl as a mobile phase, size exclusion chromatography (SEC) column removes the impurities by hydrophobic adsorption as well; molar masses obtained from both techniques thus agree when hydrophobic filters are used in bulk light scattering experiments. Diverse hydrodynamic flow retardation effects including slalom chromatography behavior are shown to substantially bias molar mass distributions obtained for ultra-high molar mass (UHM) HA, unle...

Solutions of poly(N-isopropylacrylamide) (PNIPA) with added sodium dodecyl sulfate (SDS) were investigated by light scattering methods at temperatures of 15-40°C. The formation of well-defined nanoparticles of PNIPA was observed on heating at low SDS additions. The effects of PNIPA and SDS concentrations and the molecular weight of PNIPA on nanoparticle parameters were investigated. An interpretation based on stabilization of PNIPA nuclei by SDS was suggested.

Dynamic light scattering was used to investigate the dynamics of sodium poly(styrene sulfonate) and fully neutralized poly(acrylic acid) gels as a function of the degree of swelling and weight ratio of cross-linking agent. It was shown that the collective diffusion coefficient increases with increasing degree of swelling and that the diffusion coefficient shows stronger concentration dependence than predicted by scaling arguments. For gel samples measured at the swelling equilibrium, the diffusion coefficient increases with increasing gel concentration for both gel systems.

A time-resolved small-angle light scattering apparatus equipped with azimuthal integration by means of a conical lens or software analysis of scattering patterns detected with a CCD camera was developed. Averaging allows a significant reduction of the signal-to-noise ratio of scattered light and makes this technique suitable for investigation of phase separation kinetics. Examples of applications to time evolution of phase separation in concentrated statistical copolymer solutions and dissolution of phase-separated domains in polymer blends are given.

The association of styrene−methyl methacrylate statistical copolymers in the selective solvent acetone (a thermodynamically good solvent for poly(methyl methacrylate and bad for polystyrene) was examined by static and dynamic light scattering methods. In dilute solutions, the dynamics was dominated by a single fast mode, whereas in semidilute solutions two modes were generally seen, with fast and slow mean relaxation times. The fast dynamic mode was related to the cooperative diffusion mode. The slow mode was associated with dynamics of polymeric clusters formed by the random association process. Experimental results were interpreted in terms of the coupling model of partly penetrating polydispersed clusters formed by random association of copolymers.

Dynamic properties of styrene-methyl methacrylate (MMA) statistical copolymer solutions in benzene, a solvent isorefractive with MMA, were studied by dynamic light-scattering spectroscopy (DLS) and by pulsed-field-gradient NMR (PFG-NMR). Two separate dynamic processes were found from the DLS results in the semidilute region. The fast process was related to the cooperation diffusion mode. The slow diffusive process was attributed to the dynamics of composition fluctuations. The diffusion coefficient of the slow process has the magnitude similar to the self-diffusion coefficient determined by PFG-NMR. Dynamic property of the slow polydispersity mode were qualitatively interpreted in terms of the theory developed for diblock copolymers.

We examine the influence of the diverging concentration fluctuations near a spinodal on the dynamics of branched polymer solutions in the vicinity of a sol−gel transition. Dynamic light scattering ...

High optical purity polystyrene (PS), poly(methyl methacrylate) (PMMA) and styrene-methyl methacrylate statistical copolymers (S-MMA) were prepared. Light scattering measured on polymeric glasses depends on the chemical composition of the polymer and on the refractive index of the plastifier added. An isorefractive plastifier reduces considerably the scattering values for the copolymers S-MMA, while having no significant effect on the scattering of PMMA. A plastifier with a refractive index different from that of the polymer raises distinctly the light scattering values in all cases. It has been shown that the isorefractive plastifier has a favourable effect on attenuation loss of polymeric optical fibers (POF) obtained from the copolymer S-MMA 2/1. Optisch hochreine Glaser wurden aus Polystyrol (PS), Polymethylmethacrylat (PMMA) und statistischen Styrol-Methylmethacrylat-Copolymeren (S-MMA) hergestellt. Die an diesen Glasern gemessene Lichtstreuung hangt von der chemischen Zusammensetzung des Polymeren und dem Brechungsindex des zugesetzten Weichmachers ab. Ein isorefraktiver Weichmacher verringert die Streuwerte der S-MMA-Copolymeren, hat aber keinen signifikanten Einflus auf das Streuverhalten von PMMA. Ein Weichmacher mit einem vom Polymeren verschiedenen Brechungsindex verschlechtert die Streuwerte in allen untersuchten Fallen. Es wird gezeigt, das ein isorefraktiver Weichmacher die Dampfungseigenschaften von aus dem Copolymeren S-MMA 2/1 gezogenen polymeren Lichtleitern verbessert.

The effect of multiple light scattering on a homodyne intensity auto-correlation function and photocount distribution of scattered light has been studied. The analysis of quasielastic light scattering data has shown that even a small contribution (several percent) of multiple light scattering to the total scattered light intensity can be distinguished and identified by the Laplace transform inversion of the corresponding intensity auto-correlation function. The photocount distribution reflects the coherence time changes of the scattered light only.

Quasielastic light scattering was used to study samples of epoxy resins prepared by copolymerization in bulk of diglycidylether of Bisphenol A with Jeffamine D 400. First cumulants of the autocorrelation functions obtained with dilute solutions of these samples were determined, as well as distributions of sizes of the clusters below the gel point.

Interactions between micelles of the three-block copolymer polystyrene-block-(hydrogenated polybutadiene)-block-polystyrene in selective solvent mixtures 1,4-dioxane/0-30 vol. % n-heptane were investigated by light scattering methods. Experimental values of the second virial coefficient, A 2, from the time-averaged light scattering data agree with theoretical values for the hard sphere model. The diffusion viral-coefficient values, k D, from quasielastic light scattering measurements agree within the limits of experimental error with the experimental k D value determined by Kops-Werkhoven and coworkers for spherical silica particles. Virtually monodisperse block-copolymer micelles appeared to be suitable for testing theoretical results obtained for hard sphere interactions.

The purpose of this communication is to report relaxation time distributions derived from dynamic light scattering measurements, close to the gelation threshold, for PMMA gels swollen in butylacetate. The distributions are composed of contributions from two diffusive (K2-dependent) modes corresponding to collective diffusion of the gel matrix and the interdiffusive modes of sol components inside the gel matrix. While the collective diffusion is typified by a unique value of the correlation length, the latter are described by a very broad distribution due to substantial polydispersity. K-independent structural relaxations, which are usually present in semidilute solutions in poor solvents, are not present.

Three-block copolymers poly[styrene-b-(ethene-co-butene)-b-styrene], where the middle aliphatic block amounts to about 70 wt.-%, form micelles in 1,4-dioxane with an aliphatic core and a polystyrene shell. The basic characteristics concerning the ratio unimer/micelles, the micellar molar mass, the radius of gyration, and the hydrodynamic radius were determined by combining the results of light scattering, small-angle X-ray scattering, photon correlation spectroscopy, osmometry, and viscometry. The characteristics of the micelles, approximated by the model of concentric spheres, were calculated from the data of light scattering and small-angle X-ray scattering. From a comparison of the geometric and hydrodynamic dimensions of the micelles it follows that in dilute solutions they behave like rigid spheres.

Temperature and concentration behaviour of the dynamic structure factor of poly(styrene) was measured in a marginal solvent (dibutyl phthalate) by quasielastic light scattering. Both the concentration and temperature dependences of the hydrodynamic radius of the polymer coil and of the hydrodynamic blob size were found to follow the scaling laws predicted by theory. A relation m + b = -1 between exponents m and b for the concentration and temperature dependence of the blob size in semidilute solutions has been derived, and its validity was checked experimentally.

Micelles of a block copoymer poly(styrene/butadiene/styrene) with cores consisting of polybutadiene blocks were stabilized in dilute solutions by UV radiation in the presence of a photo-initiator and also by fast electrons, and micelles of a block copolymer poly(styrene/ethene-co-1-butene/styrene) with cores formed by the aliphatic blocks were stabilized by fast electrons, in dilute solutions. Stabilization of micelles, i. e., crosslinking of the chains in micellar cores as well as the properties of stabilized micelles were studied by conventional light scattering, by light scattering photon correlation spectroscopy and by gel permeation chromatography.

The response of quasielastic light scattering to the polydispersity of scattering objects has been investigated. A new method of the polydispersity index determination has been suggested, suitable for the range 1.02 ⪬ Mw/Mn ⪬ 2.0 and consisting in the measurement of the dependence of the apparent decay time on the correlator sampling time. The polydispersity index can be determined by comparing these dependences with the theoretical ones obtained using correlation curves simulated for various values of the polydispersity index, assuming lognormal and Schulz-Zimm distributions of molecular weights. The test measurements on polystyrene standards having molecular weights in the range 9 103 – 20.6 106 give polydispersity index values Mw/Mn that are in a good agreement with those given by the manufacturer. The polydispersity index for polystyrene having the molecular weight Mw = 20.6 106 thus determined was Mw/Mn = 1.35.

A three-block copolymer poly(styrene-block-hydrogenated butadiene-block-styrene) forms in 1,4-dioxane and 1,4-dioxane/30 vol% n-heptane mixture spherical micelles with aliphatic cores and polystyrene shells. Properties of these micelles near critical conditions, i.e., above the critical micelle concentration (CMC) and below the critical micelle temperature (CMT) have been studied by light scattering. Integral light scattering is proportional to the weighted contributions of the molar masses of two species present in the solutions under study. Quasielastic light scattering, on the other hand, can provide in principle, the values of diffusion coefficient pertaining predominantly to micelles. Experimental data, namely concentration dependences of the diffusion coefficient and of the apparent mass-average molar mass, strongly deviate from the expected pattern predicted by the model of closed association. The deviation consists in an increase of both molar mass and hydrodynamic radius of micelles in a particular concentration region above CMC.

Quasielastic light scattering measurements on transparent poly (2-hydroxyethyl methacrylate) (PHEMA) gels were performed under temperature equilibrium conditions at several temperatures from 40 to 80°C. All observed correlation functions departed from the single exponential decay with a long-time limit. The asymptotic value relaxation frequency Γa decreased steeply with decreasing temperature. The observed temperature dependence of Γa is interpreted as resulting from polymer fluctuations near the glass transition of weakly swollen PHEMA gels.

Colloidal particles of three-block copolymers polycaprolactam-block-polystyrene-block-polycaprolactam, formed in a solvent mixture toluene/2,2,3,3-tetrafluoropropanol as a good solvent of polycaprolactam, were studied by static and dynamic light scattering and transmission electron microscopy. Two kinds of spherical multimolecular particles differing in size were found in the solution. The smaller particles containing tens of copolymer molecules were interpreted as regular copolymer micelles, and the larger particles formed from thousands of copolymer molecules were interpreted as associates of these micelles.

On compare les donnees theoriques et experimentales sur la distribution du comptage de photons de la lumiere diffusee par un petit nombre de particules en utilisant la distribution de probabilite de l'intensite log normale. On presente une table et des nomogrammes permettant de determiner de petits nombres de particules diffusantes a partir de la distribution de comptage de photons de la lumiere diffusee

Measurements of composite autocorrelation functions extending over a broad time range on semidilute theta solutions of polystyrene in cyclohexane are reported. Three mathematical methods were used to obtain the corresponding distribution functions of decay times, F(τ). Results of the different methods are in mutual agreement. It is found that F(τ) consists of several separated bands. The shortest and longest decay times have been extracted from F(τ) and, on the basis of their concentration and angular dependences, attributed to the gel mode and reptation process, respectively.