Relaxation in Amorphous Polymers

what is the molecular basis for this range of behavior To explore this let us first consider a hypothetical isolated chain in space, then imagine stretching this chain instantaneously so that there is a new end-to-end distance. The distribution of bond angles (trans, gauche, etc.) changes to accommodate the conformations that are allowed by the new constraints on the ends. Because it 

The various relaxation processes that occur in entangled chains may be so complex and coupled that only a smooth distribution or spectrum of relaxation times may actually exist. Nevertheless, the concept of modes and even models that are characterized by just one or two relaxation rimes is useful when you start out in this subject, as it gives you a good feel for what is going on. Just keep in mind that the dynamics of entangled polymer chains is a complex subject and one where we presently only have rough theoretical models. 

Given all these caveats, how fast are relaxation processes in amorphous polymers In low molecular weight liquids relaxations are very fast, occurring in time frames of the order of 10 10 secs. In a polymer melt (T T) 

General Electric scientists and engineers could find no practical applications for it Academics, of course, loved the material, as it was a beautiful teaching tool with which to demonstrate the fundamentals of viscoelasticity. It wasn t until 1949 that it was marketed as a children s toy. And as they say, the rest is history. Silly Putty is still being produced in Pennsylvania and remains a favorite plaything for children and adults alike. 

But why has silly putty such unusual characteristics It is thought that the relatively weak inter-molecular bonds formed by the transfer of electron pairs from oxygen to boron are largely responsible. These bonds act like temporary or labile cross-links, which are continually making and breaking, and the physical and mechanical properties of the material then depend upon the time scale of the experiment 

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The theory of two potential wells of nearly equal depth has been used to explain secondary relaxations in amorphous polymers. Recent results by L. C. E. Struik led to the result... 

Uchidoi, M., Adachi, K., and Ishida, Y., Volume relaxation in amorphous polymers around glass-transition temperature, Polym. J., 10, 161-167 (1978). 

Ingram, M.D., Imrie, C.T., Ledru,)., and Hutchinson, J.M. (2008) Unified approach to ion transport and stmctural relaxation in amorphous polymers and glasses. J. Phys. Chem. B, 112, 859-866. 

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