M. Roos, K. Schäler, A. Seidlitz, T. Thurn-Albrecht, K. Saalwächter.
NMR study of interphase structure in layered polymer
morphologies with mobility contrast: disorder and confinement
effects vs. dynamic heterogeneities.
Colloid. Polym. Sci. 292, 1825-1839 (2014).
Nanostructured multiphase polymers with mobility
contrast, such as semicrystalline polymers or block copolymers
with two separate glass transitions, are usually characterized
by the presence of an interphase material with inbetween
mobility. This interphase is often assumed to form a
contiguous layer between the adjacent main phases, possibly
exhibiting a mobility gradient. Here, we present evidence
from proton low-field NMR experiments based upon the spin
diffusion effect that suggests less trivial possible arrangements.
A numerical analysis of the NMR data based upon a
2D lattice model demonstrates that a part of the mobile phase
must be in rather direct contact with the rigid phase. Tentatively,
we assume an island-like distribution of the interphase,
or its location within the rigid phase, with sizes on the scale of
a few nanometers. We observe qualitatively the same phenomenon
in a semicrystalline polymer, poly(?-caprolactone),
and in a lamellar poly(styrene)-poly(butadiene) block copolymer,
suggesting that the phenomenon has some degree of
universality. We hypothesize that the non-trivial location of
the interphase results from either a higher than onedimensional
constraint imposed by the surrounding rigid
phase and disorder effects arising from local roughness or
thickness distributions or from the intrinsic dynamic heterogeneity
length scale of material close to the glass transition.