| Abstract
| - Dynamic light scattering measurements of the diffusion coefficient D and the Rayleigh ratioRθ are reported for dextran molecules confined in agarose gel networks of various concentrations. In thiscondition, the light scattered by the dextran is some 2 orders of magnitude less intense than that fromthe agarose. Three molecular weights of dextran were investigated: 7 × 104, 5 × 105, and 2 × 106 gmol-1. For the lowest molar mass it is confirmed that, below the dextran overlap concentration c*, theproduct DRθ is independent of the agarose concentration, showing that the reduction of the rate of diffusioninside the gel is the result of a decrease in the osmotic pressure in the confined geometry. For the highermolar masses, entanglement effects between the dextran and the network become noticeable in the morehighly concentrated gels. The dynamic light scattering intensity measurements are also found to yieldreasonable estimates of the molar mass Mw and radius of gyration RG of the trapped dextran molecules.The second virial coefficient A2 is positive, indicating that the agarose−water matrix acts as a good solventfor dextran, but the ratio of RG to the hydrodynamic radius is less than 1.5. These results are interpretedin terms of branching of the dextran molecule.
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