AbstractBinary mixtures of the perdeuterated and protonated isotopes of four amorphous polymerspolystyrenes, 1,4-polybutadienes, 1,2-polybutadienes, and 1,2-polybutenes – have been examined by small-angle neutron scattering (SANS). In each case, evaluation of the SANS results based on the RPA theory of de Gennes indicates non-ideal mixing characterized by a Flory-Huggins interaction parameter 10-4 < χ 10-3. All four χ parameters can be closely predicted based on the measured change in the carbon-hydrogen bond polarizability with deuterium substitution. These findings are discussed in the context of past SANS studies of amorphous polymers.