In this study we report small-angle neutron-scattering measurements of cyclic and linear polydimethyl-siloxane (PDMS) in the melt. It has been suggested that due to the presence of topological constraints, rings in the melt may be more compact than Gaussian chains. We show that the cyclic chains are partially collapsed and do not follow Gaussian statistics: the weight-average radius of gyration Rg,w is found to be proportional to Mw0.53 and Mw0.40 in the case of linear and cyclic PDMS, respectively. The results are in agreement with recent computer simulations, which predict Rg to be proportional to N2/5, where N is the degree of polymerisation.
|Number of pages||3|
|Journal||Applied Physics A: Materials Science and Processing|
|Issue number||Supplement 1|
|Publication status||Published - Dec 2002|