Neutron scattering polymer diffusion

There is a fundamental question concerning the nature of the self-motion of protons in glass-forming polymers. In Sect. 4.1 we have shown that the existing neutron scattering results on the self-correlation function at times close to the structural relaxation time r (Q-region 0.2t) with a KWW-like functional form and stretching exponents close to jSsO.5. 

Finally, the study of the protons of the polymer chain measured by incoherent neutron scattering allows the identification of two distinct types of motion (a) a vibrational motion of the Debye-Waller type and (b) a slow jump-like diffusive motion of the whole chain confined within the volume restricted by... 

Rg is the polymer radius of gyration, Xs is the value of the x parameter (see Section 2.3.1) at the spinodal point, and D is the mutual diffusion coefficient of the two polymer components. Bates and Wiltzius (1989) have confirmed the predictions of Eqs. (9-4) and (9-5) for early-time SD of binary blends of perdeuterated and protonated 1,4-polybutadiene. Neutron-scattering studies of SD on a similar system by Jiimai et al. (1993a, 1993b) also confirm the Cahn theory at early times, but the spinodal growth rates deviate somewhat from Eq. (9-5). 

Figured displays simulated form factors for a multiarm star polymer of varying functionality and a hard sphere [41], The high-g asymptotic behavior, characteristic of the coil structure, is absent in the latter case. A handicap in the experimental determination of P(g) is often the narrow-g range accessible by the scattering techniques that can be overcome through the combination of low-g light scattering and high-g X-ray and/or neutron scattering (utilized on the same system). Size and shape also determine the translational diffusion Dq of the nanoparticles in dilute solution, and hence Dq can prove the consistency of the scattering results.

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