Structure properties of dextran. 2. Dilute solution

Dilute solution properties of 13 dextrans with different molar masses in wa ter and 0.5 M NaOH were investigated. Seven of these samples were products of Sigma prepared by bacteria from Leuconostoc mesenteroides, one was obtai ned by fractionation of the dextran with the highest molar mass, and five s amples were obtained by degradation via controlled acid hydrolysis. Static and dynamic light scattering, viscometry and analysis of the reducing end g roup were applied. The molar mass dependencies of the radius of gyration R- g, the hydrodynamic: radius R-h, the second virial coefficient A(2) and the intrinsic viscosity [eta] for the nonfractionated samples were determined. The results are compared with data from the literature. Size exclusion chr omatography in on-line combination with multiple-angle laser light scatteri ng and viscosity detection revealed different calibration curves M-i vs V-e for the studied samples. The molar mass dependencies of the radii and intr insic viscosities could be measured. The data of the radii of gyration from four fractionated samples were found to form one common curve. The intrins ic viscosities, on the other hand, gave two curves, one for the Sigma sampl e and another one for the acid-degraded samples. These findings are discuss ed in comparison with the nonfractionated samples. The polydispersity of de xtrans, like those for other hyperbranched polysaccharides, increased stron gly with M-w but weaker than predicted by theory. Generalized ratios rho = R-g/R-h and V-r = A(2)M(w/)[eta] are considered and discussed in comparison with data from other laboratories and compared with predicted values. The coil-coil interpenetration function Psi and the solvent-coil draining funct ion Phi, were found to increase with the molar mass as a result of increasi ng branching density.