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Influence of Torsional Stiffness Upon Temperature Response of a Polymeric Chain.
ROHM AND HAAS CO HUNTSVILLE AL REDSTONE RESEARCH LABS
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The influence of torsional stiffness upon the temperature dependence of the mean square end-to-end polymer chain distance r squared was studied parametrically for six different polymer chain models. The equations for r squared expressed in terms of the torsional potential energy, were differentiated with respect to temperature and the resulting equations were evaluated numerically. The magnitudes and locations of the secondary barrier heights, angular location and magnitudes of the energy minima, angular location of the maximum barrier, spacing of the extrema, and the number of extrema were each found to play a significant role in the value of the predicted thermal expansion coefficients. The coefficients were also found to critically depend upon the relative energy ratio and were usually a highly non-linear function of this ratio. Transitions between positive and negative values of the thermal expansion coefficients were found to exist and to depend upon the torsional potential shape, energy ratio, and the polymer chain model. Author
APPROVED FOR PUBLIC RELEASE