In this report a survey is given on structure and properties of polyacrylamide homopolymers (PAAm) in solution. In addition the unperturbed (theta) dimension parameters K0, 〈h2〉0/M, the characteristic ratio C∞, the steric factor σ, and the thermodynamic interaction parameter B were calculated from the modified Burchard-Stockmayer-Fixman procedure using polymolecularity correction and the results compared with experimental data from the literature. A comparison of the −Mw-relationship with literature data is given. It was found that dn/dc increases slightly up to Mw = 1,8 These results were obtained by consideration of the limit of the dilute solution regime, the determination of zero-shear rate intrinsic viscosities, and the molecular weight dependence of the refractive index increment dn/dc. 106 were determined in toluene at 25☌ by light scattering and viscometry measurements.Intrinsic viscosities, second and third virial coefficients A2 and A3, respectively, and mean square radius of gyration 〈RG2〉 of a polymer homologous series of narrow-molecular-weight-distribution polystyrene samples in a molecular weight range of 2000 up to 24 Daruber hinaus ubt es einen echten Verdunnungseffekt aus, was bedeutet, das die Viskositat zwischen den Werten fur die Schmelze und fur das reine Losungsmittel bei gegebener Temperatur abfallt. Das Losungsmittel hat einen zweifachen Einflus auf das Polymere: Es erniedrigt die Glastemperatur und setzt damit die Aktivierungsenergie fur den viskosen Flus herab.
Die Effekte von Konzentration und Temperatur auf die Viskositat von Polymerlosungen konnen jedoch nicht getrennt behandelt werden, da sie voneinander abhangig sind. Potenz der Polymerkonzentration verlauft. Aus der Literatur geht hervor, das die Viskositat von konzentrierten Losungen annahernd proportional der 5. Furthermore the solvent exerts a real dilution effect, causing the viscosity to fall between that of a polymer melt and that of the pure solvent at the temperature concerned.ĭie Rheologie konzentrierter Polymerlosungen zeigt eine bemerkenswerte Ubereinstimmung mit der Rheologie von Polymerschmelzen, aber sie ist komplizierter wegen eines neuen Parameters, namlich der Konzentration des Polymeren. The solvent has a dual effect on the polymer: it decreases the glass transition temperature and hence lowers the activation energy of viscous flow. The effects of concentration and temperature on the viscosity of polymer solutions, however, cannot be treated separately, since they are interrelated. The literature shows evidence that the viscosity of concentrated solutions is roughly proportional to the 5th power of the polymer concentration. The rheology of concentrated polymer solutions shows a remarkable correspondence with that of polymer melts, but is more complicated due to a new parameter: the concentration of the polymer.
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