| Popis: |
Small-angle X-ray scattering (SAXS) has been applied in obtaining the solution parameters (molecular mass M, radius of gyration Rg, radius of gyration of cross-section Rq, mass per unit length Mu, and persistence length a ∗ ) of a poly(acrylic acid) (PAA) sample in dioxane at 25°C. The M and Rg values measured from SAXS were 552 000 Da (daltons) and 292 A, respectively. These values are in reasonable agreement with those obtained from solution viscometry measurements on the same sample of PAA in dioxane at 30°C ( M = 567 000 Da and R g = 227 A ). The Rq and a ∗ values obtained from SAXS were 6.1 A and 14.4 A, respectively. The Mu value measured from SAXS is 27.9 Da A−1, in excellent agreement with the model (theoretical) value of 28.6 Da A−1 calculated from the structure and molecular mass of the monomer unit. The length L (= M/Mu = 19 790 A) obtained from SAXS thus corresponds to the contour length of the molecule and not to the ‘hydrodynamic’ length (i.e. the length the chain assumes in the fluid medium). |
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