Solvent Effects and a Test of the Theory of Hypochromism

The hypochromism of the 2600-Å absorption band of isotactic polystyrene (relative to atactic polystyrene) has been examined. It is shown that there are important solvent effects which modify the magnitude of the hypochromism. The theory of Tinoco and Rhodes does not include explicit solvent interactions and cannot account for all our experiments. For the case of chloroform as solvent, the theory is in (fortuitous) agreement with experiment if calculations are performed carefully and convergence is established (±10 rings for 2% residual). If the influence of the solvent may be neglected in this case, it may be concluded that the results obtained are consistent with the retention of local structure when isotactic polystyrene passes from the crystalline phase into solution.