Materials World Network: In-situ NMR Studies of Processing and Deformation of Polymer/Clay Nanocomposites
Final Report Abstract
The effect of mechanical load on unfilled and filled polymers has been investigated by nuclear magnetic resonance (NMR). Poly(propylene) and poly(propylene) filled with fluoromica have been investigated. Low-field NMR has been applied to investigate solid semi-crystalline polymers under uniaxial stress in situ. Restrictions of the polymer mobility under stress have been found. Under constant extension these restriction of the molecular mobility relax with time. The longitudinal relaxation time T1 provides a measure for the effective contact between the polymer and the filler containing paramagnetic impurities. Uniaxial deformation of the filled polymer results in shorter T1 which indicates that the contact area between the polymer and the filler increased as a result of delaminating the clay sheets. Polymer melts have been studied under shear in a Couette cell by rheo NMR. Increased mobility has been found with increasing temperature as expected. Shearing the unfilled polymer results in enhanced mobility of the polymer chains. This effect dominates the possibly underlying chain ordering. No such effect has been observed for the nanoparticle-filled polymer. Restrictions of the chain mobility from the interaction with the filler do not permit sufficient enhancement of the mobility to dominate the signatures from chain ordering in the NMR data. The longitudinal relaxation time T1 has been used as an indirect measure of the sample temperature. An increase of the sample temperature as a result from shearing is thus excluded. Only small differences in the conformation of the polymer in contact with the filler particle compared to the bulk polymer have been observed by interface-selective solid-state NMR like REDOR dephasing from the filler.
Publications
- Formation of single-walled aluminosilicate nanotubes from molecular precursors and curved nanoscale intermediates. J. Am. Chem. Soc. 133 (2011) 5397
Yucelen, G. I.; Choudhury, R. P.; Vyalikh, A.; Scheler, U.; Beckham, H. W.; Nair, S.
- Solid-State NMR of Polymers under Mechanical Stress. AIP conference proceedings 1330 (2011) 109-112
Ute Böhme, Karsten Gelfert and Ulrich Scheler
