Analysis of measurements of the static scattering function by electron and X-ray diffraction, ofthedynamicscatteringlaw hyneutronscattering,andofinfraredand Raman spectrapointsattheimportant role of twin helix-reversal defects for the molecular dynamics in the intermediate phase and high-temperature phase (modifications IV and I) of poly(tetrafluoroethy1ene). In contrast to single helix-reversal defects, these twin defects constitute a local perturbation which can move along the chain without affecting remote units. One species, the 'coherent" twin defect, possesses a particularly low formation energy, since it retains the twist long-range order along the chain. Formation of the defects occurs mainly in the intermediate phase.In the high-temperature phase a saturation is observed. The steep increase in the defect concentration in the intermediate phase followed by the equilibration in the high-temperature phase can he understood as a transition between a disordered State controlled by intra-and intermolecular forces to one which is only determined by the intramolecular potentials. In spite of the disorder in the helices, an orientational shortrange order is retained for sequences in adjacent chains. The degree of order is related to the defect concentration. The reorientation of the C h group resulting from the formation and motion of the twin defects occurs with rates in the range of 10-100 GHz. Orientational shorbrange order leads to a slowing down.

The kinetics of the microphase separation transition in a diblock copolymer of polystyrene/ polyisoprene was studied with time-resolved small-angle X-ray scattering. Using synchrotron radiation it was possible to determine the structure factor in time intervals of 10 s. The relaxation of the structure factor after temperature jumps within the disordered regime was found to be wave vector dependent in accordance with Cahn-Hilliard theory. For quenches from the disordered into the ordered state an additional, slow process was found which consists mainly of a decrease in the width of the first-order reflection. It is interpreted as the perfectioning of the lamellar order. Whereas the corresponding relaxation time had been found to decrease strongly with supercooling for shallow quenches, it is found to increase again for deeper quenches.

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Time-resolved small-angle X-ray scattering is used to investigate the time dependence of structure formation at the ordering transition in bulk diblock copolymers. After a quench from the disordered into the ordered state two relaxation processes are found on well-separated time scales. The slow process displays an unusual temperature dependence and is discussed as a nucleation phenomenon.

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