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doi: 10.1002/masy.19991450103pmid: N/A
Nanoparticles with diameters from 1–100 nm are used in large quantities for very different applications. A precise determination of the important physical quantities (which are responsible for the application properties) such as diameter, particle size distribution, and surface is therefore very essential. The most common methods for the determination of these quantities are analytical ultracentrifugation (AUC) and dynamic light scattering (DLS). The paper demonstrates the techniques of getting a precise characterization of nanoparticles and suggests a new method for the correction of the sedimentation coefficient and its distribution with respect to the diffusion coefficient.
doi: 10.1002/masy.19991450104pmid: N/A
We present the study of the adsorption of a non‐ionic surfactant onto latex particles by small‐angle X‐ray scattering (SAXS). The analysis of the process of adsorption by SAXS is discussed in detail. It is demonstrated that SAXS allows to monitor the gradual built‐up of the surface layer with increasing amount of added surfactant. SAXS also allows to obtain the radial volume fraction of the hydrophilic tails of the surfactant. Possible limitations of this analysis are discussed.
doi: 10.1002/masy.19991450105pmid: N/A
The article handles some aspects of polyelectrolyte research investigated during the last ten years at the university of Osnabrück. They are: counterion binding, polyion complexation, and polyion condensation. Fundamental features are presented that are common to the behaviour of most polyions. Another intention is to bridge a gap between synthetic and biological polyelectrolyte research. For this purpose, DNA condensation is reviewed in some detail.
Oertel, U.; Buchhammer, H.‐M.; Müller, M.; Nagel, J.; Braun, H.‐G.; Eichhorn, K.‐J.; Sahre, K.
doi: 10.1002/masy.19991450106pmid: N/A
An improved method for the preparation of uniform dispersions of non‐stoichiometric polyelectrolyte complexes on the basis of maleic acid copolymers and poly(diallyldimethylammonium chloride) was developed. The dispersed particles showed a narrow size distribution on the nm scale and were used as model systems for the investigation of their adsorption on different model surfaces. A combination of ATR‐FTIR, SPR, ellipsometry and SEM was useful for the monitoring of the adsorption process of individual colloid particles and may lead to a quantitative description of the adsorption process. For a better understanding of the underlying principles and interactions organic model surfaces which meet the requirements of the different methods are required.
doi: 10.1002/masy.19991450107pmid: N/A
Many liquid chromatographic (LC) separations of macromolecules are influenced or directly based on adsorption of solutes on column packing. In the case of well known size exclusion chromatography (SEC), adsorption effects are usually unwanted and therefore suppressed. Still they appear in many SEC systems and may badly affect precision of results obtained. In other LC methods applicable to high polymers, adsorption is deliberately combined with exclusion. The aim is to discriminate complex polymer systems which exhibit more than one single distribution of their molecular characteristics. The main goals of such combinations include either a controlled increase or a full suppression of separation selectivity according to one molecular characteristics. Most important so far known exclusion‐adsorption compensation methods allowing to suppress dependence of LC retention volumes on polymer molar mass are reviewed. The discussion is accomplished with a presentation of newly developed full adsorption ‐ desorption (FAD) method which can be combined with various LC procedures. A very useful combination represents the on‐line FAD/SEC procedure which enables also to study adsorption and desorption phenomena in the systems solid surface ‐ solvent ‐ macromolecules.
Kuckling, Dirk; Adler, Hans‐Juergen P.; Arndt, Karl‐Friedrich; Ling, Long; Habicher, Wolf Dieter
doi: 10.1002/masy.19991450108pmid: N/A
A series of temperature and pH sensitive polymers which contain both temperature and pH sensitive components were synthesised by copolymerization of N‐isopropylacrylamide (NIPAAm) and acrylamide derivatives containing a spacer and a sensitive headgroup. The cloud point and heat of transition (ΔHPT) of aqueous solutions of polymers with various compositions were measured by means of DSC. The observed cloud points and ΔHPT values strongly depend on the polymer composition and the pH value. The irradiation of dimethylmaleinimide groups (DMIAAm) bearing copolymers with UV light resulted in crosslinking of the polymers. The prepared thin layers showed fast temperature dependent swelling with transition temperatures similar to the uncrosslinked polymers.
Knörgen, Manfred; Heuert, Uwe; Schneider, Horst; Kuckling, Dirk; Richter, Sven; Arndt, Karl‐Friedrich
doi: 10.1002/masy.19991450110pmid: N/A
The kinetics of diffusion in polymers ranges from simple Fickian diffusion to higher order diffusion, such as Case II diffusion1‐2). The conventional method for determining the characteristics of solvents into polymer matrices is by measuring the mass uptake of the polymer as the solvent penetrates the matrix. However, since such measurements perform observations at a macroscopic level, little information has been obtained relating to the nature of the solvent in the polymer matrix and the mechanisms of the processes that control the diffusion. Nuclear magnetic resonance (NMR) imaging (‘MRI’) has been used to observe the penetration of solvents into solid systems in realtime. The method provides a one‐ or more‐dimensional image of the density and the mobility of the solvent in a material or of the network changes of the material itself due to the softening influence of the solvent. The first (imaging of the solvent) can be used for a quantitative measurement of the diffusion whereas the observation of the network gives information about the changing of the network (mobility, de‐crystallization…) during the swelling process. For example the diffusion of organic solvents in some polymeric materials (natural rubber, water gels (PNIPAAm), and nematic diblock‐copolymers) are investigated.
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