CONFORMATIONAL DISTRIBUTION OF POLY(ETHYLENE OXIDE) IN MOLTEN PHASE AND IN AQUEOUS-SOLUTION BY QUASI-ELASTIC AND INELASTIC LIGHT-SCATTERING

We report on measurements performed by Raman scattering, PCS and ultra sonic velocity measurements on poly(ethylene oxide) both in the molten phase and in aqueous solution. Increasing the polymerization degree, m, the Raman analysis of the D-LAM (disordered longitudinal acoustic m ode) spectral contribution to the pure polymers reveals a behaviour of the centre frequency and linewidth which has been connected with an o ligomer-polymer transition occurring at m congruent to 13. In aqueous solutions the frequency increase towards values corresponding to the c rystal ones and the sharpening of the D-LAM spectral contribution indi cate that the addition of water,destroys the intermolecular interactio ns and stiffens the coil structure. In addition evidence of a more ord ered conformation with respect to the melt phase is presented. The tem perature analysis of the D-LAM band and of the hydrodynamic radius, ev aluated by PCS, reveals that the solvent power of water increases up t o T = 45 degrees C, decreasing at higher temperature. Interpreted in c onjunction with ultrasonic data these apparently differing findings pr ovide a coherent interpretative key capable of encompassing the struct ural properties of our systems. Finally the role played by inter- and intra-molecular interactions is discussed within the framework of curr ent theories.