Segmental diffusion molecular weight

Radical polymerizations of macromonomers are greatly influenced by the diffusion control effect [44]. Segmental diffusivity and translational diffusivity of the growing chains of macromonomers are strongly affected by the feed concentration and the molecular weight of the macromonomers. Furthermore, there is little difference in the degree of polymerization between macro-... 

In a solid polymer, low-molecular-weight species diffuse with D 10 7— 10 9cm2 s 1 [67]. Segments of a macromolecule with the free valence diffuse still more slowly (T>eff 10 9 10 12cm2 s-1)- With the lifetime of P02 of 10-100 s, the distance covered by this radical... 

The rate of growth of polymer-salt complexes can provide fundamentally important information that is difficult to determine otherwise. The rate of crystal growth of (PEO)3 NaSCN from its undercooled liquid was measured and used to determine values for the diffusion coefficients of Na" " and SCN (Lee, Sudarsana and Crist, 1991). Also it was shown that the rate of the salt diffusion is independent of the molecular weight of the polymer for PEO molecular weights above 10. This result is fully consistent with the concept that ion motion is due to local segmental motion of the polymer. 

Stokes radius of a polymer segment = r8. Applying our experimental data to Equation 2, we obtained r8 10 A. This value seems to be quite reasonable. On the other hand, we can set D8 in relation to experimentally determined diffusion constants of a certain polymer. This enables us to attribute a molecular weight of the segment to D8. For MMA, we obtain M , Mma 2000. 

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