Solid amorphous polymers, molecular

As emphasized above, in contrast to common thermoplastics, thermoplastic elastomers contain a very soft phase (with Tg around —50°C), which is in a liquid state at room temperature and is characterized by a viscosity closer to that of low-molecular-weight liquids rather than a solid amorphous polymer. In this respect it seems useful to recall that the molecular weight of the PTMG and PEG used is 1000, i.e. one is dealing with typical oligomer systems. For this reason it looks reasonable to accept that such a liquid will be characterized by a negligibly small microhardness, in the equation ... 

PHOTOCHEMISTRY AND MOLECULAR MOTION IN SOLID AMORPHOUS POLYMERS... 

Photochemistry and Molecular Motion in Solid Amorphous Polymers 91... 

The deviations from exponential relaxation at long as well as short times ( long time tails ) represented by these equations are not often found for simple molecules in liquids but are comnon in molecular solids amorphous polymers and polymer solutions raising questions as to why this should be ... 

Recall that the diffusion coefficient in a glass of water equals 10 " - 10 cmVs, in melted polymer - 10 in a solid amorphous polymer - 10 , and in crystalline polymer - lO -lO" cmVs. Thus the molecule s motion and speed at transition from liquid low molecular compoimd to solid crystalline polymer may vary by 20 orders of magnitude or higher. Hence, a transition from kinetic area (when the reaction rate is defined by reactivities of the substances) to diffusion area (when the situation is completely defined by reagent delivery to the interaction site and the Frank-Rabinovich cage effect) may occur. 

GuiUet, J. E., Photochemistry and molecular motion in solid amorphous polymers, Adv. Photo-chem., 14, 91, 1988. 

So far we have outlined the conceptual framework in which we discuss charge transfer in organic semiconductors. It is based on a molecular picture where the molecular unit is considered central, with interactions between molecular units added afterwards. For amorphous molecular solids and for molecular crystals this approach is undisputed. In the case of semiconducting polymers, a conceptually different view has been proposed that starts from a one-dimensional (ID) semiconductor band picture, and that is generally known as the Su-Schrieffer-Heeger (SSH) model [21-24]. 

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