| 研究実績の概要 |
The major outcomes of the project are as follows:
(1) Disparity in the size of monomers is sufficient for polymer blends to exhibit anomalous mixing rules for quantities related to entanglements such as the plateau modulus, or equivalently, the tube diameter. We have verified this for blends of polymers that were nearly identical except their monomer sizes were either in the ratio 2:1 or 3:1. The local liquid-like structure of the blend was investigated using the radial distribution function (RDF). The RDF indicated that the mixing was nonrandom with an increased probability for the small monomers to be the non-bonded neighbors of the large monomers. We suspect that the origin of the anomalous mixing rules is related to this nonrandom mixing and efforts are underway to generalize the available mixing rules to account for this effect.
(2) We also investigated the dynamics of blends with monomer size disparity. To simplify matters, we started with unentangled melts. Surprisingly, we found that the terminal relaxation time of the chains with the large monomers increased while that of the chains with the small monomer decreased upon blending. In other words, upon blending, the dynamics of the slow component became even slower while that of the fast component became even faster. This also appears to be related to the nonuniform mixing alluded to earlier. We are currently trying to quantitatively understand the effect of nonuniform mixing on the monomer and chain dynamics. Future work will include the effect of entanglements and chain stiffness on the dynamics.
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