Static and quasielastic light scattering from solutions of poly(ethyleneoxide) in methanol

Static and quasielastic light scattering measurements on dilute and semi-dilute solutions of monodisperse poly(ethylene oxide) in methanol have been carried out at 25 degrees C. Four PEO fractions having weight average molecular weights equal to 31500, 90000, 230000 and 904000 and degrees of polydispersity lower than 1.1 were used. The angular dependence of Zimm plots shows no downturn at low angles. In addition, monomodal distribution curves were computed from the quasielastic measurements, confirming that PEO are molecularly dispersed in methanol at 25 degrees C. Experimental scaling laws for the radius of gyration R-G. the second Virial coefficient A(2) and the hydrodynamic radius R-H have been determined. The exponents characterizing these scaling laws confirm that methanol is a good solvent for this polymer. Finally, the overlap concentrations corresponding to the transition between the dilute and semi-dilute regimes were determined for the different PEO samples. (C) 1998 Elsevier Science Ltd. All rights reserved.