CHAIN CONFORMATION OF ISOTACTIC POLYSTYRENE IN THE BULK AMORPHOUS STATE AS REVEALED BY SMALL-ANGLE NEUTRON-SCATTERING

The conformation of labeled isotactic polystyrene (IPSD) in the bulk amorphous state has been investigated using the technique of small-angle neutron scattering (SANS) for two kinds of matrices: IPS matrices and atactic polystyrene (APS) matrices. The experiments have shown in the case of IPS matrices that the chain presents Gaussian behavior for samples molded above melting temperature Tm and rapidly quenched to room temperature. For APS matrices two phenomena have been observed. At first, the iso tactic tagged chains exhibit Gaussian character when they are dispersed in APS matrices having the same or higher molecular weight. In this case the radius of gyration decreases drastically with temperature. In return, IPSD chains behavior diverges from Gaussian state in a certain range of temperature by using APS matrices of lower molecular weight. This is particularly shown by the variation of the scattered intensity in the intermediate range which is proportional to q-1.66 [q = (4 π/λ) sin (θ/2)] for samples molded at 180°C and q-2.5 for samples molded at 200°C instead of q-2 for Gaussian coil. However, these abnormal effects vanish when the samples are prepared above melting temperature Tm. All the results are discussed in terms of conformational models. © 1979, American Chemical Society. All rights reserved.