Akademik Veri Yönetim Sistemi
Journal of Applied Polymer Science, cilt.101, sa.1, ss.203-216, 2006 (SCI-Expanded)
The unperturbed molecular dimensions of poly(ethylene glycol) (PEG) samples (of different molecular weights) have been evaluated in aqueous solutions from viscosity measurements at 25, 30, 35, and 40°C. The unperturbed dimension, Kθ, has been determined from extrapolation methods, i.e., Kurata-Stockmayer-Fixman (KSF), Inagaki-Suzuki-Kurata (ISK), and Berry equations. The hydrodynamic expansion factor, αn, as well as the unperturbed root-mean-square end-to-end distance, (r2) 01/2, found for the system indicated that the polymer coils contract as the temperature is raised from 25 to 40°C. The long-range interaction (excluded volume) parameter, B, was also evaluated and a significant decrease was found for the PEG/water system between 25 and 40°C. The theta temperatures, θ, were obtained from the temperature dependence of (1/2 - x) and the second virial coefficient was detected in the temperature interval of 25-40°C for the system and quite a good agreement with the calculated values evaluated via extrapolation and interpolation methods was observed. The thermodynamic interaction parameter x was evaluated through the sum of the individual values of enthalpy and entropy dilution parameters, XH and Xs for PEG samples. All the unperturbed molecular dimensions of PEG/water system were calculated and compared according to Mw and Mn values of PEG samples. Calculated values were interpreted mainly on the basis of hydrogen-bond formation between polymer segments and PEG-water molecules in solution. © 2006 Wiley Periodicals, Inc.