Dimensions of a Flexible Polymer Chain in the Bulk and in Solution

POLYMER molecules dispersed in a good solvent expand1 significantly beyond the size expected from purely random orientation of the segments. In the bulk, however, there are theoretical reasons2 which indicate that the molecule should recover its “Gaussian” size. For a long time experimental evidence for this assertion was missing. Several people (G. Allen and S. F. Edwards, personal communication and refs. 3 and 4) have recently recognized that such evidence may be obtained from a small angle neutron scattering experiment. One of them4 has already published results on polymethyl methacrylate. We discuss here some results for atactic polystyrene.