Unperturbed dimensions of polytetrahydrofuran

Phase separation techniques have been utilised to establish the following theta‐conditions for polytetrahydrofuran : isopropanol at 44.6°C, di‐ethyl malonate at 33.5°C and a mixture of ethyl acetate/ n ‐hexane (22.7/77.3 wt.‐%) at 30.4°C. The entropy, enthalpy, and free energy pair interaction parameters ψ 1 , ϰ 1 , and χ 1 were also obtained. Light scattering measurements were conducted in isopropanol alone and the second virial coefficient found to be zero, thus verifying theta‐conditions. For all three solvent systems the K UHN ‐M ARK ‐H OUWINK viscosity exponent ν was confirmed to be 0.50, but a unique value was not exhibited by the corresponding K Θ . Some reasons are proposed to account for this. From each K Θ the steric factor σ is calculated to be 1.67 (in isopropanol), 1.69 (in di‐ethyl malonate) and 1.75 (in the mixed solvent). These values lie between those for polyethylene oxide and polyethylene.