-The dynamics of polymer melts is well reflected in the complex shear compliance J*(o,T,M) measured in wide ranges of frequency and temperature and f o r various molecular weights. In the frame of the meander model all typical features of J * ( U ,T,M) are quantitatively described:(1) J&N is due to intra-meander shear, and decreases by incorporating pairs of chain ends within the superstructure folds, i.e. with decreasing M. (2) This shear motion is guaranteed by a certain amount of edge-dislocations (with Burgers vector b equal to the chain distance d -for some polymers equal to d/2). The glass relaxation and its activation diagram are understood by asking f o r the probability for just this amount of dislocation segments to be present. The dielectric relaxation strengths and those of the thermal properties support the chosen segment lengths. Neglecting flow,the stress-strain curves of uncrosslinked high molecular weight polymer melts can be derived by taking into account intra-and inter-meander shear deformation. INTRODUCTIONIn this paper experimental data shall be summarized which characterize the two main relaxations in uncrosslinked amorphous polymers, the glass process and the viscoelastic flow relaxation. These data (among others) should be explained by any molecular model of the levels of order in amorphous polymers to establish its availability for an understanding of more complex macroscopic properties. Here a quantitative interpretation will be given in the frame of the meander model, the suppositions and derivation of which are discussed elsewhere ( 1 , Z ) . The main topic will be the linear viscoelastic behavior in shear of polymer melts, which is best represented by the complex shear compliance J* (w,T,M) in the range between the glassy state (higho or low T) and the viscous flow region ( l o w w or high T). In fig. 1 -3

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A new high-pressure cell as useful equipment for a polarizing microscope is described. Measurements in a temperature range between −40 and +270 °C under hydrostatic pressures up to 300 MPa allow for example the observation of polymer morphology and phase transitions. In addition to a documentation on video and photograph, respectively, the computer-controlled light intensity measurement offers the possibility of a quantitative analysis. Investigations on the phase diagram of poly(diethylsiloxane) have been carried out and show, that the transition temperature from mesophase to isotropic melt decreases with increasing pressure for pressures above 160 MPa.