Dynamics of Polystyrene in a Theta Solvent Investigated by Neutron Spin Echo

Abstract

Dynamics of polystyrene in cyclohexane at the theta temperature was investigated by neutron spin echo. The intermediate scattering function up to 50 nano seconds could be observed, then the result was quantitatively compared with the Zimm theory, where the Gaussian approximation for polymer dynamics and the preaveraging approximation for hydrodynamics effect are applied. We found that the theory agrees with the experimental result only in low momentum transfer \(Q\) range, (\(Q \times b < 1\) with the effective bond length \(b\)), which deviates gradually at higher \(Q\). The experimentally observed decay rate is approximately factor 0.5 smaller than the theoretical prediction at the experimental \(Q\) maximum (\(Q \approx 0.1\) Å−1).