Biaxial deformation of polymer networks and deuteron quadrupolar interactions

摘要

The use of deuterium quadrupolar interactions to study deformation in polymer networks is well-established. In particular, the quadrupole splitting, obtained from a small deuterated probe molecule diffusing within the network, is known to be sensitive to the network strain, with the splitting dependence on the deformation ratio λ = L/L_0 given by Δω ～ (λ~2 - λ~(-1)). A typical probe molecule might be a deuterated monomer or oligomer of the same chemical composition as the polymer network, or some other small deuterated molecule which is soluble within the network. As this molecule diffuse within the network, it occasionally collides with the polymer segments and suffers steric hindrance, thus being slightly constrained in available orientation. This steric sensitivity to the polymer segment orientation is sometimes termed a "pseudonematic interaction". It enables the probe molecule to "inherit" the orientational order of the host network, albeit significantly reduced by a numerical factor whose precise magnitude depends on the subtle details of interaction averaging.