Branched conformational properties of macromolecules in close relation to chemical synthesis. II. Influence of excluded volume interactions.

The description of perturbed particle conformations needs as a prerequisite the algorithm of unperturbed chains which is outlined in Paper I [J. Chem. Phys.

Branched conformational properties of macromolecules in close relation to chemical synthesis. I. Unperturbed structures.

Similar to uniform linear chains, the unperturbed structure of branched polymers forms the basis for the development of a theory on the effect of excluded volume interactions. A clear overview over the skeleton of such complex structures is obtained with a simplifying modification of the general branching theory. The use of probability generating functions permits a direct incorporation of essential details from the chemical synthesis in this branching theory.

Dendronized Hyperbranched Macromolecules: Soft Matter with a Novel Type of Segmental Distribution.

Dendronization of a hyperbranched polyester with different generation dendrons leads to pseudo-dendritic structures. The hyperbranched core is modified by the divergent coupling of protected monomer units to the functional groups. Compared to dendrimers, the synthetic effort is significantly less, but the properties are very close to those of high-generation dendrimers.

Is the universal law valid for branched polymers?

A matter of phis: The size of macromolecules is determined by the "universal calibration" based on the Flory-Fox equation (see scheme). The effect of the segmental density of real branched systems on this equation is investigated. To study this effect, accurately prepared polymers with discrete molecular properties were characterized in detail and precisely evaluated.

Simultaneous determination of substituent patterns in partially acid hydrolyzed O-Me/O-Me-d(3)-cellulose and quantification of the obtained oligomers by HPLC-ESI-MS.

Substituent patterns in oligosaccharide derivatives obtained from methyl cellulose were determined up to DP10 by electrospray ionization mass spectrometry employing separation of the oligomer fractions by HPLC. Oligosaccharides were labeled with meta-aminobenzoic acid after perdeuteromethylation and partial hydrolysis of methyl cellulose, enabling simultaneous quantification according to DP by HPLC/UV. Control of the HPLC-method was performed with a defined oligomer mixture obtained from β-cyclodextrin.

Solution properties of conventional gum arabic and a matured gum arabic (Acacia (sen) SUPER GUM).

Dilute solution properties of two specially matured gum arabic samples (EM1 and EM2) were compared to the conventional gum (EM0) using static light scattering. The apparent molar mass (M(w,app) and radius of gyration (R(g,app)) for the three samples showed unusual concentration dependence. These data were satisfactorily interpreted by a simple association model that takes into account the repulsive interaction among clusters, which allowed us to obtain the true molar mass (Mw(0)) and radius of gyration (Rg(0)).

Carbanilation of cereal beta-glucans for molecular weight determination and conformational studies.

Cereal beta-glucans can form aggregates in aqueous solution. The presence of aggregates in cereal beta-glucan solutions led to inaccurate determination of molecular weights and it was believed that intermolecular hydrogen bonding caused the aggregation. To eliminate aggregates, a carbanilation method for molecular weight determination of cereal beta-glucans was developed.

Chain dynamics in microgels: poly(N-vinylcaprolactam-co-N-vinylpyrrolidone) microgels as examples.

Microgels are highly swollen colloids built up of flexible cross-linked chains. We studied the static and dynamic light scattering (LS) behavior of thermosensitive microgels based on N-vinylcaprolactam and N-vinylpyrrolidone prepared by precipitation copolymerization in H2O (CP-1) and D2O (CP-2). Striking differences in behavior were observed in the two solvents.

Molecular characterisation of soybean polysaccharides: an approach by size exclusion chromatography, dynamic and static light scattering methods.

Water soluble polysaccharides from soybean (SSPS) have a pectin-like structure and are used as stabilisers in acidified beverages. Physicochemical properties such as structure, molecular weight and shape or conformation are primary factors controlling their functional properties. Two soybean polysaccharides, a native SSPS and a modified SSPS treated with beta-(1-->4)-D-galactosidase (GPase/SSPS) were studied by dynamic and static light scattering (DLS, SLS) and size exclusion chromatography (SEC).

Shear-induced mixing and demixing in aqueous methyl hydroxypropyl cellulose solutions.

The influence of shear flow on the phase separation of aqueous methyl hydroxypropyl cellulose solutions was investigated by means of rheoturbidity and online rheo small angle light scattering (SALS) experiments. In semidilute solution shear-induced mixing was observed and the cloud curve was shifted to higher temperatures with increasing shear rate. With higher concentrated solutions, however, shear-induced demixing was found.

Structure of artificial cytoskeleton containing liposomes in aqueous solution studied by static and dynamic light scattering.

The structure of three types of liposomes (egg yolk phosphatidylcholine (EPC) without modification and EPC vesicles containing cross-linked N-isopropylacrylamide (NIPAM) networks of low and a high concentration inside the vesicles) were analyzed by static and dynamic light scattering. Upon polymerization the network was assumed to become attached to the membrane by reactive anchoring monomers. For the sample of high poly(NIPAM) content the polymer network was assumed to fill the whole space in the vesicles.

Peculiarities of aqueous amaranth starch suspensions.

Among the starches the granules from amaranth starch (a. hypochondriacus, amylopectin type) are singular because of their extremely small size of 1-3 microm and high uniformity. However, large spherical particles of 30-80 microm in diameter were observed from spray-dried amaranth starch by environmental scanning electron microscopy (ESEM) which exhibited a characteristic fine structure.