Internal motions high polymers

Heijboer [28] has reported the dynamic mechanical properties of poly(nethacrylate)s with different size of the saturated ring as side chain. The y relaxation in these polymers is attributed to a conformational transition in the saturated ring. In the case of poly(cyclohexyl methacrylate), the transition is between the two chair conformations in the cyclohexyl ring. However, this type of internal motion in hindered by rather high intramolecular barriers, which can reach about 11 kcal mol-1. 

We shall show by a very simple example how these ideas can be transformed into mathematical relations, for it will appear later that many an important property of high polymeric substances is connected directly with the internal motions of large, chain or reticulate molecules. E. Wohlisch in 1927 advanced the idea that the tendency of rubber and muscles to contract is traceable to the thermal motion of molecules and K. H. Meyer showed in 1932 that it is not a question of the motions of entire molecules, but of links in the principal chains which cause the contraction of the extended chain by their thermal motions. The quantitative demonstration of this idea was furnished by H. Mark and his co-workers and independently by W. Kuhn the experimental proof occupies an important position in the field of high polymers. 

Polymers in solution phases have a high degree of freedom for translational and internal motion. They change their conformations randomly by Brownian movements. The purpose of this section is to see how these molecular characteristics of polymers lead to the macroscopic properties of the polymer solutions. 

A second step is necessary. Even crosslinked polymers have residual dissipative features due to internal motions of molecular segments, a type of internal viscosity. It is therefore necessary to carry out the measurements of strength at very low rates of deformation and at high temperatures, far above the glass transition temperature, to minimize energy absorption from these processes. 

N. Nemoto, Y Makita, Y. Tsunashima, and M. Kurata. Dynamic light scattering studies of polymer solutions. 3. Translational diffusion and internal motion of high molecular weight polystyrenes in benzene at infinite dilution. Macromolecules, 17 (1984), 425 30. 

Only the molten state of linear high polymers can be called with some certainty an equilibrium state which is independent of thermal history. Its heat capacity is still caused, for the largest part, by molecular vibration. In additum, conformational changes and internal rotations are possible and need to be accounted for. In general, little is known about the detailed motion in the liquid state as it applies to the l t capacities. Only liquid polyethylene melt has been analyzed in scane detail [Wunderlidi (19 )]. 

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