| Abstract: | The temperature ΘA2 at which the second virial coefficient A2 is zero for ring polystyrenes is 28.5°C in cyclohexane, independent of molecular weight in the range 2 × 104 to 4.5 × 105. This cannot be explained solely by the Candau–Rempp–Benoit theory, which takes into account the effect of segment density on ΘA2 The radius of gyration of a ring is found to be approximately one-half that of a linear polymer with the same molecular weight. The intrinsic viscosities η] and intrinsic translational friction coefficients f] of ring polystyrenes with molecular weights ranging from 7 × 103 to 4.5 × 105 have been measured in cyclohexane at 34.5°C (Θ, the Flory theta temperature for linear polystyrenes) and in toluene (a good solvent). The results are compared with those for linear polystyrene. It is found that the Mark–Houwink exponent is less than one-half in cyclohexane at Θ. In toluene it is 0.67 compared to 0.73 for linear polystyrene. The hydrodynamic measurements suggest that large rings are less expanded than the linear polymers with the same molecular weight, contrary to many predictions. |
