Showing papers by "Peter Schurtenberger published in 1993"

On the application of polymer renormalization group theory to polymer-like microemulsions

Abstract: We report on the application of results from conformation space renormalization group theory for semi-dilute polymer solutions to “equilibrium polymers” such as worm-like micelles or microemulsions. We have tested this approach with data from an extensive static light scattering study of lecithin water-in-oil (w/o) microemulsions. We demonstrate that one can construct a universal curve $(M_{\rm w}/RT)(\partial\Pi/\partial c)$ versus a reduced concentration X∼c/c*, where c* is the overlap concentration, from the experimentally determined values of the osmotic compressibility if a power law of the form Mw∼cα for the c-dependence of the average particle size is assumed. We show that one can thus obtain information from static light scattering experiments on the concentration dependence of both the micellar size distribution and the intermicellar interaction effects, i.e., on the weight average molecular weight Mw(c) and the static structure factor S(0, c).

Murphy’s law of particle sizing: comparison of the size distributions of lecithin liposomes obtained by dynamic light scattering and electron microscopy

Abstract: Frequently, a mean radius is used to characterize colloidal systems. As most real systems possess a broad size distribution, such a mean size will hardly be sufficient to describe the studied system, and more detailed information on the size distribution is desired. Because different techniques imply a different weighting of the individual sizes, the obtained size distributions depend on the method used. On the other hand, a number or mass distribution is the most desirable result for many experiments, and therefore the measured distribution must be transformed. Although such a transformation is often possible, the limitations of the measuring technique and, hence, of the transformed distribution must be considered. — ALecithin lipsomes were used as model colloids. Their size distributions were investigated with dynamic light scattering and both classical freeze-fracture electron microscopy and cryo transmission electron microscopy. Algorithms were developed in order to convert the thus obtained size distributions into “true” number distributions.

Solution properties and light scattering measurements of poly(2,5‐pyrimidinediylterephthalamide)

Abstract: A Series of chains of different molecular weight of the fully aromatic polyamide poly(2,5-pyrimidinediylterephthalamide)1 (PPYMT) in the solvents 96 wt.-% sulfuric acid and methanesulfonic acid have been characterized by means of static and dynamic light scattering, dilute solution viscosimetry and measurements of the critical polymer volume fraction for the onset of a nematic phase. The experimental results are in good agreement with a model of stiff worm-like chains for the solution conformation of PPYMT, and the persistence length is estimated to be ca. 150 A (lower limit: 50–100 A).

The structure of biopolymer-containing microemulsions: A light-scattering study at the optical match point

Abstract: In this study, we focus on the size and structure perturbations induced in the reverse micellar system upon solubilization of the enzyme α-chymotrypsin by using light-scattering techniques. The knowledge of the geometrical parameters is very important in order to develop a good theoretical model of the driving forces responsible for polymer and biopolymer solubilization in microemulsions. Since the size difference between the empty reverse micelles and the average size measured in the biopolymer-containing solution is often very small, the size distribution changes induced by the presence of biopolymers cannot be determined unambiguously by normal light-scattering experiments.