Torsional energy barriers, molecular modelling

To develop an understanding of the sub-T relaxational processes of PSF and the nature of molecular motions involved, new forced torsional dynamic medianical data for PSF samples with well-controlled thermal histories were studied. To assist in the assignment of molecular motions, geometry optimized CNDO/2 (Complete Neglect of Differential Overlap) and molecular orbital (MO) calculations of model compounds were used to predict energy barriers to rotation. These energy barriers are compared to the activation energies determined from the dynamic mechanical data for each relaxation. Details of the CNDO/2 and molecular mechanics techniques used may be found elsewhere. 

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