Bimodal Distribution of Relaxational Modes for the Helix-Coil Transition in Poly(oxymethy1ene)
نویسنده
چکیده
The helix-coil transition in poly(oxymethy1ene) has been investigated by using the recently developed dynamic rotational isomeric state (DRIS) model and the related matrix multiplication technique. The conditional probability P,(h/h) that a chain originally in the perfect helical form will preserve its state unchanged at a later time T is evaluated for various chain lengths and temperatures. The transition to the coiled structure in an originally fully ordered helix is found to exhibit a bimodal relaxation, indicated by a plateau in the time decay curves of the conditional probabilities, before restoration of equilibrium distribution. This intermediate quasi-steady state preceding full relaxation is attributed to an equilibrium between perfect helices and chains possessing a single defect in the form of a trans bond, interrupting sequences of gauche bonds of the same sign.
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