SMALL-ANGLE X-RAY-SCATTERING OF POLY(ACRYLIC ACID) IN SOLUTION .1. DIOXANE

Small-angle X-ray scattering (SAXS) has been applied in obtaining the solution parameters (molecular mass M, radius of gyration R(g), radius of gyration of cross-section R(q), mass per unit length M(u), and per sistence length a) of a poly(acrylic acid) (PAA) sample in dioxane at 25 degrees C. The M and R(g) values measured from SAXS were 552 000 D a (daltons) and 292 Angstrom, respectively. These values are in reason able agreement with those obtained from solution viscometry measuremen ts on the same sample of PAA in dioxane at 30 degrees C (M = 567 000 D a and R(g) = 227 Angstrom). The R(q) and a values obtained from SAXS were 6.1 Angstrom and 14.4 Angstrom, respectively. The M(u) value meas ured from SAXS is 27.9 Da Angstrom(-1), in excellent agreement with th e model (theoretical) value of 28.6 Da Angstrom(-1) calculated from th e structure and molecular mass of the monomer unit. The length L (= M/ M(u) = 19 790 Angstrom) obtained from SAXS thus corresponds to the con tour length of the molecule and not to the 'hydrodynamic' length (i.e. the length the chain assumes in the fluid medium).