ISSN:
1600-5767
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
SAXS by solutions of monodisperse polystyrene at intermediate concentrations has been studied for the solvents having only a small volume-exclusion effect, such as methyl ethyl ketone (MEK) and cyclohexane (CH). Both the density-density correlation function of segments in solution and the osmotic compressibility, as obtained from the absolute intensity at zero angle, were measured for different concentrations and the results were successfully analysed by means of the recent theory of Moore [J. Phys. (Paris), (1977), 38, 265–271] . According to the theory, in the semi-dilute poor-solvent regime the concentration C, dependence of the screening length ξ, and the scattered intensity at zero angle I(0) are given by {{1}\over{\xi^{2}C}} = 12NA{{B_1}\over{A^2}} + 36N2A{{B_2}\over{A^2}}C and {{(\Delta Z)^2}\over{I(0)}} = B1 + 3NAB2C, where M is the molecular weight of a polymer molecule, NA Avogadro's number and A2M the mean square end-to-end distance of an unperturbed chain; m2B1 and m3B2 are respectively the binary and ternary cluster integrals (or the first and the second irreducible integrals) for segments in solution, m being the molecular weight of a segment. ΔZ is the number of excess mole electrons per unit mass of segments. The measured concentration dependences were in agreement with the above prediction and the values of B1 and B2 were obtained.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0021889878013758
