- R. Pérez-Aparicio, M. Schiewek, J. López Valentín, H. Schneider, D. R. Long, , M. Saphiannikova, P. Sotta, K. Saalwächter, M. Ott.
Local Chain Deformation and Overstrain in Reinforced Elastomers:
An NMR Study
Macromolecules 46, 5549-5560 (2013).
A molecular-level understanding of the strain response of
elastomers is a key to connect microscopic dynamics to macroscopic
properties. In this study we investigate the local strain response of vulcanized,
natural rubber systems and the effect of nanometer-sized filler particles, which
are known to lead to highly improved mechanical properties. A multiplequantum
NMR approach enables the separation of relatively low fractions of
network defects and allows to quantitatively and selectively study the local
deformation distribution in the strained networks matrix on the microscopic
(molecular) scale. We find that the presence of nondeformable filler particles
induces an enhanced local deformation of the matrix (commonly referred to as
overstrain), a slightly increased local stress/strain heterogeneity, and a reduced
anisotropy. Furthermore, a careful analysis of the small nonelastic defect
fraction provides new evidence that previous NMR and scattering results of
strained defect-rich elastomers cannot be interpreted without explicitly taking the nonelastic defect fraction into account.